movements and site fidelity of the giant manta ray, manta birostris, in the komodo marine park,...
TRANSCRIPT
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6amp7 5th Street Radhakrishnan Salai Chennai Tamil Nadu India ndash 600004Re Marine Biology DOI101007s00227-008-0988-x
Movements and site fidelity of the giant manta ray Manta birostris in the Komodo Marine ParkIndonesia
Authors Heidi Dewar middot Peter Mous middot Michael Domeier middot Andreas Muljadi middot Jos Pet middot Jeff Whitty
Permission to publishI have checked the proofs of my article andq I have no corrections The article is ready to be published without changes
q I have a few corrections I am enclosing the following pagesq I have made many corrections Enclosed is the complete article
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Metadata of the article that will be visualized in OnlineFirst
ArticleTitle Movements and site fidelity of the giant manta ray Manta birostris in the Komodo Marine Park IndonesiaArticle Sub-Title
Article CopyRight - Year Springer-Verlag 2008(This will be the copyright line in the final PDF)
Journal Name Marine Biology
Corresponding Author Family Name DewarParticle
Given Name HeidiSuffix
Division National Oceanographic and Atmospheric Administration
Organization Southwest Fisheries Science Center
Address 8604 La Jolla Shores Dr 92037 La Jolla CA USA
Email heididewarnoaagov
Author Family Name MousParticle
Given Name PeterSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name DomeierParticle
Given Name MichaelSuffix
Division
Organization Pfleger Institute of Environmental Research
Address 901B Pier View Way 92054 Oceanside CA USA
Author Family Name MuljadiParticle
Given Name AndreasSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name PetParticle
Given Name JosSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name WhittyParticle
Given Name JeffSuffix
Division
Organization Murdoch University
Address South Street 6150 Murdoch WA Australia
Schedule
Received 31 August 2007
Revised
Accepted 24 April 2008
Abstract Despite their large size and frequent occurrence in near-shore tropical habitats little published informationis available on the movements and behaviors of the giant manta ray Manta birostris and what factors influencevisitation patterns To examine the movements of manta rays in the Komodo Marine Park Indonesia anacoustic array was installed at up to seven sites in the park between 2000 and 2003 A total of 41 acoustictags were deployed in three separate deployments in 2000 2001 and 2002 Mantas were recorded in the parkfor up to 526 days with an average duration of 183 plusmn 136 days when mantas made from 3 to 303 individualvisits to different sites (median 58 visits) There was a clear preference for three sites that comprised over90 of manta activity The most popular site (German Flag) was off the southern tip of Komodo Island inan area with a high degree of bathymetric structure Examination of the longest records suggests some sitepreference with 5 of 7 individuals spending greater than 90 of their time at the location where they weretagged Using a general linear model it was possible to examine the effects of daytime lunar phaseaggregation site season and tidal phase on visitation patterns The vast majority of visits were recorded duringdaylight hours at all sites The strongest effects of both the lunar and tidal phase were apparent in the northernsites with the most visits occurring when tidal intensity was the greatest during full and new moons Thestrongest seasonal pattern was observed in the south where no mantas were recorded during the first quarterin any year This coincides with an increase in temperature and reduction of productivity in this regionassociated with monsoonal shifts The long-term fidelity indicates that marine-protected areas centered aroundaggregation sites could help protect this species from overexploitation
Footnote Information Communicated by R J Thompson
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CR54 K Yano F Sato T Takahashi (1999)
Journal 227 Article 988
Mar Biol
DOI 101007s00227-008-0988-x
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LE TYPESET CP DISK
ORIGINAL PAPER
Movements and site Wdelity of the giant manta ray
Manta birostris in the Komodo Marine Park Indonesia
Heidi Dewar middot Peter Mous middot Michael Domeier middot
Andreas Muljadi middot Jos Pet middot JeV Whitty
Received 31 August 2007 Accepted 24 April 2008
Springer-Verlag 2008
Abstract Despite their large size and frequent occurrence
in near-shore tropical habitats little published information
is available on the movements and behaviors of the giant
manta ray Manta birostris and what factors inXuence visi-
tation patterns To examine the movements of manta rays in
the Komodo Marine Park Indonesia an acoustic array was
installed at up to seven sites in the park between 2000 and
2003 A total of 41 acoustic tags were deployed in three
separate deployments in 2000 2001 and 2002 Mantas were
recorded in the park for up to 526 days with an average
duration of 183 sect 136 days when mantas made from 3 to
303 individual visits to diVerent sites (median 58 visits)
There was a clear preference for three sites that comprised
over 90 of manta activity The most popular site (German
Flag) was oV the southern tip of Komodo Island in an area
with a high degree of bathymetric structure Examination of
the longest records suggests some site preference with 5 of
7 individuals spending greater than 90 of their time at the
location where they were tagged Using a general linear
model it was possible to examine the eVects of daytime
lunar phase aggregation site season and tidal phase on vis-
itation patterns The vast majority of visits were recorded
during daylight hours at all sites The strongest eVects of
both the lunar and tidal phase were apparent in the northern
sites with the most visits occurring when tidal intensity was
the greatest during full and new moons The strongest sea-
sonal pattern was observed in the south where no mantas
were recorded during the Wrst quarter in any year This
coincides with an increase in temperature and reduction of
productivity in this region associated with monsoonal
shifts The long-term Wdelity indicates that marine-pro-
tected areas centered around aggregation sites could help
protect this species from overexploitation
Introduction
The giant manta ray (Manta birostris DonndorV 1798) is a
monogeneric species in the subfamily Mobulinae (Family
Myliobatidae) that consists of the devil rays The giant
manta is the largest of all rays reaching a disc width of up to
67 m and 1400 kg weight (Last and Stevens 1994) Like
the largest whales and sharks manta rays are Wlter feeders
They and the other members of the subfamily funnel water
and prey into their mouths using their distinctive cephalic
lobes Prey is then Wltered from the water by modiWed gill
rakers The giant mantas are often observed feeding in
surge channels (Wilson et al 2001) on surface slicks or
near lights at night that act to concentrate prey Like the
largest Wlter feeding shark (the whale shark) manta rays
occur worldwide in tropical and subtropical waters
(Bigelow and Schroeder 1953 Last and Stevens 1994
Compagno 1999) While mantas are observed primarily in
Communicated by R J Thompson
H Dewar (amp)
National Oceanographic and Atmospheric Administration
Southwest Fisheries Science Center 8604 La Jolla Shores Dr
La Jolla CA 92037 USA
e-mail heididewarnoaagov
P Mous middot A Muljadi middot J Pet
The Nature Conservancy PO Box 80228
Jl Pengembak No 2 Sanur Denpasar 80235 Bali Indonesia
M Domeier
PXeger Institute of Environmental Research
901B Pier View Way Oceanside CA 92054 USA
J Whitty
Murdoch University South Street Murdoch WA 6150 Australia
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near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
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Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
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aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
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documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
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427
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
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446
447
448
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450
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452
453
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463
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478
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482
483
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
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531
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541
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
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and trade of whale sharks and manta rays in the Bohol Sea Phil-
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International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
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Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
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an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
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Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
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satellites with temperature data from tags on Wsh Fish Bull
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Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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tho
r P
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EC
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PR
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Dispatch 30408 No of Pages 13
LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
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Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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Fax to +44 870 622 1325 (UK) or +44 870 762 8807 (UK)To Springer Correction Team
6amp7 5th Street Radhakrishnan Salai Chennai Tamil Nadu India ndash 600004Re Marine Biology DOI101007s00227-008-0988-x
Movements and site fidelity of the giant manta ray Manta birostris in the Komodo Marine ParkIndonesia
Authors Heidi Dewar middot Peter Mous middot Michael Domeier middot Andreas Muljadi middot Jos Pet middot Jeff Whitty
Permission to publishI have checked the proofs of my article andq I have no corrections The article is ready to be published without changes
q I have a few corrections I am enclosing the following pagesq I have made many corrections Enclosed is the complete article
Date signature ______________________________________________________________________________
Metadata of the article that will be visualized in OnlineFirst
ArticleTitle Movements and site fidelity of the giant manta ray Manta birostris in the Komodo Marine Park IndonesiaArticle Sub-Title
Article CopyRight - Year Springer-Verlag 2008(This will be the copyright line in the final PDF)
Journal Name Marine Biology
Corresponding Author Family Name DewarParticle
Given Name HeidiSuffix
Division National Oceanographic and Atmospheric Administration
Organization Southwest Fisheries Science Center
Address 8604 La Jolla Shores Dr 92037 La Jolla CA USA
Email heididewarnoaagov
Author Family Name MousParticle
Given Name PeterSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name DomeierParticle
Given Name MichaelSuffix
Division
Organization Pfleger Institute of Environmental Research
Address 901B Pier View Way 92054 Oceanside CA USA
Author Family Name MuljadiParticle
Given Name AndreasSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name PetParticle
Given Name JosSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name WhittyParticle
Given Name JeffSuffix
Division
Organization Murdoch University
Address South Street 6150 Murdoch WA Australia
Schedule
Received 31 August 2007
Revised
Accepted 24 April 2008
Abstract Despite their large size and frequent occurrence in near-shore tropical habitats little published informationis available on the movements and behaviors of the giant manta ray Manta birostris and what factors influencevisitation patterns To examine the movements of manta rays in the Komodo Marine Park Indonesia anacoustic array was installed at up to seven sites in the park between 2000 and 2003 A total of 41 acoustictags were deployed in three separate deployments in 2000 2001 and 2002 Mantas were recorded in the parkfor up to 526 days with an average duration of 183 plusmn 136 days when mantas made from 3 to 303 individualvisits to different sites (median 58 visits) There was a clear preference for three sites that comprised over90 of manta activity The most popular site (German Flag) was off the southern tip of Komodo Island inan area with a high degree of bathymetric structure Examination of the longest records suggests some sitepreference with 5 of 7 individuals spending greater than 90 of their time at the location where they weretagged Using a general linear model it was possible to examine the effects of daytime lunar phaseaggregation site season and tidal phase on visitation patterns The vast majority of visits were recorded duringdaylight hours at all sites The strongest effects of both the lunar and tidal phase were apparent in the northernsites with the most visits occurring when tidal intensity was the greatest during full and new moons Thestrongest seasonal pattern was observed in the south where no mantas were recorded during the first quarterin any year This coincides with an increase in temperature and reduction of productivity in this regionassociated with monsoonal shifts The long-term fidelity indicates that marine-protected areas centered aroundaggregation sites could help protect this species from overexploitation
Footnote Information Communicated by R J Thompson
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3 Following citation IDs are not cited in text [CR54]
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Journal 227 Article 988
Mar Biol
DOI 101007s00227-008-0988-x
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ORIGINAL PAPER
Movements and site Wdelity of the giant manta ray
Manta birostris in the Komodo Marine Park Indonesia
Heidi Dewar middot Peter Mous middot Michael Domeier middot
Andreas Muljadi middot Jos Pet middot JeV Whitty
Received 31 August 2007 Accepted 24 April 2008
Springer-Verlag 2008
Abstract Despite their large size and frequent occurrence
in near-shore tropical habitats little published information
is available on the movements and behaviors of the giant
manta ray Manta birostris and what factors inXuence visi-
tation patterns To examine the movements of manta rays in
the Komodo Marine Park Indonesia an acoustic array was
installed at up to seven sites in the park between 2000 and
2003 A total of 41 acoustic tags were deployed in three
separate deployments in 2000 2001 and 2002 Mantas were
recorded in the park for up to 526 days with an average
duration of 183 sect 136 days when mantas made from 3 to
303 individual visits to diVerent sites (median 58 visits)
There was a clear preference for three sites that comprised
over 90 of manta activity The most popular site (German
Flag) was oV the southern tip of Komodo Island in an area
with a high degree of bathymetric structure Examination of
the longest records suggests some site preference with 5 of
7 individuals spending greater than 90 of their time at the
location where they were tagged Using a general linear
model it was possible to examine the eVects of daytime
lunar phase aggregation site season and tidal phase on vis-
itation patterns The vast majority of visits were recorded
during daylight hours at all sites The strongest eVects of
both the lunar and tidal phase were apparent in the northern
sites with the most visits occurring when tidal intensity was
the greatest during full and new moons The strongest sea-
sonal pattern was observed in the south where no mantas
were recorded during the Wrst quarter in any year This
coincides with an increase in temperature and reduction of
productivity in this region associated with monsoonal
shifts The long-term Wdelity indicates that marine-pro-
tected areas centered around aggregation sites could help
protect this species from overexploitation
Introduction
The giant manta ray (Manta birostris DonndorV 1798) is a
monogeneric species in the subfamily Mobulinae (Family
Myliobatidae) that consists of the devil rays The giant
manta is the largest of all rays reaching a disc width of up to
67 m and 1400 kg weight (Last and Stevens 1994) Like
the largest whales and sharks manta rays are Wlter feeders
They and the other members of the subfamily funnel water
and prey into their mouths using their distinctive cephalic
lobes Prey is then Wltered from the water by modiWed gill
rakers The giant mantas are often observed feeding in
surge channels (Wilson et al 2001) on surface slicks or
near lights at night that act to concentrate prey Like the
largest Wlter feeding shark (the whale shark) manta rays
occur worldwide in tropical and subtropical waters
(Bigelow and Schroeder 1953 Last and Stevens 1994
Compagno 1999) While mantas are observed primarily in
Communicated by R J Thompson
H Dewar (amp)
National Oceanographic and Atmospheric Administration
Southwest Fisheries Science Center 8604 La Jolla Shores Dr
La Jolla CA 92037 USA
e-mail heididewarnoaagov
P Mous middot A Muljadi middot J Pet
The Nature Conservancy PO Box 80228
Jl Pengembak No 2 Sanur Denpasar 80235 Bali Indonesia
M Domeier
PXeger Institute of Environmental Research
901B Pier View Way Oceanside CA 92054 USA
J Whitty
Murdoch University South Street Murdoch WA 6150 Australia
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near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
58
59
60
61
62
63
64
65
66
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LE TYPESET CP DISK
Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
158
159
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161
162
163
164
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167
168
169
170
171
172
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176
177
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182
183
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185
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187
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LE TYPESET CP DISK
Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
188
189
190
191
192
193
194
195
196
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201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
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238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
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LE TYPESET CP DISK
aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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LE TYPESET CP DISK
describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
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501
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503
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531
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540
541
542
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546
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548
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
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LE TYPESET CP DISK
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Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
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Metadata of the article that will be visualized in OnlineFirst
ArticleTitle Movements and site fidelity of the giant manta ray Manta birostris in the Komodo Marine Park IndonesiaArticle Sub-Title
Article CopyRight - Year Springer-Verlag 2008(This will be the copyright line in the final PDF)
Journal Name Marine Biology
Corresponding Author Family Name DewarParticle
Given Name HeidiSuffix
Division National Oceanographic and Atmospheric Administration
Organization Southwest Fisheries Science Center
Address 8604 La Jolla Shores Dr 92037 La Jolla CA USA
Email heididewarnoaagov
Author Family Name MousParticle
Given Name PeterSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name DomeierParticle
Given Name MichaelSuffix
Division
Organization Pfleger Institute of Environmental Research
Address 901B Pier View Way 92054 Oceanside CA USA
Author Family Name MuljadiParticle
Given Name AndreasSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name PetParticle
Given Name JosSuffix
Division
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name WhittyParticle
Given Name JeffSuffix
Division
Organization Murdoch University
Address South Street 6150 Murdoch WA Australia
Schedule
Received 31 August 2007
Revised
Accepted 24 April 2008
Abstract Despite their large size and frequent occurrence in near-shore tropical habitats little published informationis available on the movements and behaviors of the giant manta ray Manta birostris and what factors influencevisitation patterns To examine the movements of manta rays in the Komodo Marine Park Indonesia anacoustic array was installed at up to seven sites in the park between 2000 and 2003 A total of 41 acoustictags were deployed in three separate deployments in 2000 2001 and 2002 Mantas were recorded in the parkfor up to 526 days with an average duration of 183 plusmn 136 days when mantas made from 3 to 303 individualvisits to different sites (median 58 visits) There was a clear preference for three sites that comprised over90 of manta activity The most popular site (German Flag) was off the southern tip of Komodo Island inan area with a high degree of bathymetric structure Examination of the longest records suggests some sitepreference with 5 of 7 individuals spending greater than 90 of their time at the location where they weretagged Using a general linear model it was possible to examine the effects of daytime lunar phaseaggregation site season and tidal phase on visitation patterns The vast majority of visits were recorded duringdaylight hours at all sites The strongest effects of both the lunar and tidal phase were apparent in the northernsites with the most visits occurring when tidal intensity was the greatest during full and new moons Thestrongest seasonal pattern was observed in the south where no mantas were recorded during the first quarterin any year This coincides with an increase in temperature and reduction of productivity in this regionassociated with monsoonal shifts The long-term fidelity indicates that marine-protected areas centered aroundaggregation sites could help protect this species from overexploitation
Footnote Information Communicated by R J Thompson
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Query Details required Authorrsquos response 1 Domeier and Colin (1992) has been
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3 Following citation IDs are not cited in text [CR54]
CR54 K Yano F Sato T Takahashi (1999)
Journal 227 Article 988
Mar Biol
DOI 101007s00227-008-0988-x
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ORIGINAL PAPER
Movements and site Wdelity of the giant manta ray
Manta birostris in the Komodo Marine Park Indonesia
Heidi Dewar middot Peter Mous middot Michael Domeier middot
Andreas Muljadi middot Jos Pet middot JeV Whitty
Received 31 August 2007 Accepted 24 April 2008
Springer-Verlag 2008
Abstract Despite their large size and frequent occurrence
in near-shore tropical habitats little published information
is available on the movements and behaviors of the giant
manta ray Manta birostris and what factors inXuence visi-
tation patterns To examine the movements of manta rays in
the Komodo Marine Park Indonesia an acoustic array was
installed at up to seven sites in the park between 2000 and
2003 A total of 41 acoustic tags were deployed in three
separate deployments in 2000 2001 and 2002 Mantas were
recorded in the park for up to 526 days with an average
duration of 183 sect 136 days when mantas made from 3 to
303 individual visits to diVerent sites (median 58 visits)
There was a clear preference for three sites that comprised
over 90 of manta activity The most popular site (German
Flag) was oV the southern tip of Komodo Island in an area
with a high degree of bathymetric structure Examination of
the longest records suggests some site preference with 5 of
7 individuals spending greater than 90 of their time at the
location where they were tagged Using a general linear
model it was possible to examine the eVects of daytime
lunar phase aggregation site season and tidal phase on vis-
itation patterns The vast majority of visits were recorded
during daylight hours at all sites The strongest eVects of
both the lunar and tidal phase were apparent in the northern
sites with the most visits occurring when tidal intensity was
the greatest during full and new moons The strongest sea-
sonal pattern was observed in the south where no mantas
were recorded during the Wrst quarter in any year This
coincides with an increase in temperature and reduction of
productivity in this region associated with monsoonal
shifts The long-term Wdelity indicates that marine-pro-
tected areas centered around aggregation sites could help
protect this species from overexploitation
Introduction
The giant manta ray (Manta birostris DonndorV 1798) is a
monogeneric species in the subfamily Mobulinae (Family
Myliobatidae) that consists of the devil rays The giant
manta is the largest of all rays reaching a disc width of up to
67 m and 1400 kg weight (Last and Stevens 1994) Like
the largest whales and sharks manta rays are Wlter feeders
They and the other members of the subfamily funnel water
and prey into their mouths using their distinctive cephalic
lobes Prey is then Wltered from the water by modiWed gill
rakers The giant mantas are often observed feeding in
surge channels (Wilson et al 2001) on surface slicks or
near lights at night that act to concentrate prey Like the
largest Wlter feeding shark (the whale shark) manta rays
occur worldwide in tropical and subtropical waters
(Bigelow and Schroeder 1953 Last and Stevens 1994
Compagno 1999) While mantas are observed primarily in
Communicated by R J Thompson
H Dewar (amp)
National Oceanographic and Atmospheric Administration
Southwest Fisheries Science Center 8604 La Jolla Shores Dr
La Jolla CA 92037 USA
e-mail heididewarnoaagov
P Mous middot A Muljadi middot J Pet
The Nature Conservancy PO Box 80228
Jl Pengembak No 2 Sanur Denpasar 80235 Bali Indonesia
M Domeier
PXeger Institute of Environmental Research
901B Pier View Way Oceanside CA 92054 USA
J Whitty
Murdoch University South Street Murdoch WA 6150 Australia
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LE TYPESET CP DISK
near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
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Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
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aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
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536
537
538
539
540
541
542
543
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546
547
548
549
550
551
552
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555
556
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560
561
562
563
564
565
566
567
568
569
570
571
572
573
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
581
582
583
584
585
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
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and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
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in the northeastern PaciWc with an automated algorithm that esti-
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satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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tho
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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Au
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of
Organization The Nature Conservancy
Address Jl Pengembak No 2 Sanur PO Box 80228 80235 Denpasar Bali Indonesia
Author Family Name WhittyParticle
Given Name JeffSuffix
Division
Organization Murdoch University
Address South Street 6150 Murdoch WA Australia
Schedule
Received 31 August 2007
Revised
Accepted 24 April 2008
Abstract Despite their large size and frequent occurrence in near-shore tropical habitats little published informationis available on the movements and behaviors of the giant manta ray Manta birostris and what factors influencevisitation patterns To examine the movements of manta rays in the Komodo Marine Park Indonesia anacoustic array was installed at up to seven sites in the park between 2000 and 2003 A total of 41 acoustictags were deployed in three separate deployments in 2000 2001 and 2002 Mantas were recorded in the parkfor up to 526 days with an average duration of 183 plusmn 136 days when mantas made from 3 to 303 individualvisits to different sites (median 58 visits) There was a clear preference for three sites that comprised over90 of manta activity The most popular site (German Flag) was off the southern tip of Komodo Island inan area with a high degree of bathymetric structure Examination of the longest records suggests some sitepreference with 5 of 7 individuals spending greater than 90 of their time at the location where they weretagged Using a general linear model it was possible to examine the effects of daytime lunar phaseaggregation site season and tidal phase on visitation patterns The vast majority of visits were recorded duringdaylight hours at all sites The strongest effects of both the lunar and tidal phase were apparent in the northernsites with the most visits occurring when tidal intensity was the greatest during full and new moons Thestrongest seasonal pattern was observed in the south where no mantas were recorded during the first quarterin any year This coincides with an increase in temperature and reduction of productivity in this regionassociated with monsoonal shifts The long-term fidelity indicates that marine-protected areas centered aroundaggregation sites could help protect this species from overexploitation
Footnote Information Communicated by R J Thompson
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3 Following citation IDs are not cited in text [CR54]
CR54 K Yano F Sato T Takahashi (1999)
Journal 227 Article 988
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ORIGINAL PAPER
Movements and site Wdelity of the giant manta ray
Manta birostris in the Komodo Marine Park Indonesia
Heidi Dewar middot Peter Mous middot Michael Domeier middot
Andreas Muljadi middot Jos Pet middot JeV Whitty
Received 31 August 2007 Accepted 24 April 2008
Springer-Verlag 2008
Abstract Despite their large size and frequent occurrence
in near-shore tropical habitats little published information
is available on the movements and behaviors of the giant
manta ray Manta birostris and what factors inXuence visi-
tation patterns To examine the movements of manta rays in
the Komodo Marine Park Indonesia an acoustic array was
installed at up to seven sites in the park between 2000 and
2003 A total of 41 acoustic tags were deployed in three
separate deployments in 2000 2001 and 2002 Mantas were
recorded in the park for up to 526 days with an average
duration of 183 sect 136 days when mantas made from 3 to
303 individual visits to diVerent sites (median 58 visits)
There was a clear preference for three sites that comprised
over 90 of manta activity The most popular site (German
Flag) was oV the southern tip of Komodo Island in an area
with a high degree of bathymetric structure Examination of
the longest records suggests some site preference with 5 of
7 individuals spending greater than 90 of their time at the
location where they were tagged Using a general linear
model it was possible to examine the eVects of daytime
lunar phase aggregation site season and tidal phase on vis-
itation patterns The vast majority of visits were recorded
during daylight hours at all sites The strongest eVects of
both the lunar and tidal phase were apparent in the northern
sites with the most visits occurring when tidal intensity was
the greatest during full and new moons The strongest sea-
sonal pattern was observed in the south where no mantas
were recorded during the Wrst quarter in any year This
coincides with an increase in temperature and reduction of
productivity in this region associated with monsoonal
shifts The long-term Wdelity indicates that marine-pro-
tected areas centered around aggregation sites could help
protect this species from overexploitation
Introduction
The giant manta ray (Manta birostris DonndorV 1798) is a
monogeneric species in the subfamily Mobulinae (Family
Myliobatidae) that consists of the devil rays The giant
manta is the largest of all rays reaching a disc width of up to
67 m and 1400 kg weight (Last and Stevens 1994) Like
the largest whales and sharks manta rays are Wlter feeders
They and the other members of the subfamily funnel water
and prey into their mouths using their distinctive cephalic
lobes Prey is then Wltered from the water by modiWed gill
rakers The giant mantas are often observed feeding in
surge channels (Wilson et al 2001) on surface slicks or
near lights at night that act to concentrate prey Like the
largest Wlter feeding shark (the whale shark) manta rays
occur worldwide in tropical and subtropical waters
(Bigelow and Schroeder 1953 Last and Stevens 1994
Compagno 1999) While mantas are observed primarily in
Communicated by R J Thompson
H Dewar (amp)
National Oceanographic and Atmospheric Administration
Southwest Fisheries Science Center 8604 La Jolla Shores Dr
La Jolla CA 92037 USA
e-mail heididewarnoaagov
P Mous middot A Muljadi middot J Pet
The Nature Conservancy PO Box 80228
Jl Pengembak No 2 Sanur Denpasar 80235 Bali Indonesia
M Domeier
PXeger Institute of Environmental Research
901B Pier View Way Oceanside CA 92054 USA
J Whitty
Murdoch University South Street Murdoch WA 6150 Australia
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near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
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LE TYPESET CP DISK
Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
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LE TYPESET CP DISK
aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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LE TYPESET CP DISK
describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
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491
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
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(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
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Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
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Bigelow HB Schroeder WC (1953) Fishes of the Western North
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Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
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Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
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Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
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Dewar H (2002) Preliminary report manta ray harvest in Lamakera
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Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
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Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
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DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
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LE TYPESET CP DISK
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Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
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Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
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Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
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Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
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Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
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Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
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Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
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Holm KJ Burger AE (2002) Foraging behavior and resource partition-
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Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
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Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
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the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
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Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
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Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
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Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
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McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
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Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
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Musick J A (1999) Ecology and conservation of long-lived marine ani-
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Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
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Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
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Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
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Shanks AL (1983) Surface slicks associated with tidally forced internal
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Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
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Sims DW Nash JP Morritt D (2001) Movements and activity of
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Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
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Sugimoto T (1975) EVects of boundary geometries on tidal currents
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Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
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Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
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Tont SA (1975) Deep scattering layers patterns in the PaciWc
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Author Query Form
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Query Details required Authorrsquos response 1 Domeier and Colin (1992) has been
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3 Following citation IDs are not cited in text [CR54]
CR54 K Yano F Sato T Takahashi (1999)
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ORIGINAL PAPER
Movements and site Wdelity of the giant manta ray
Manta birostris in the Komodo Marine Park Indonesia
Heidi Dewar middot Peter Mous middot Michael Domeier middot
Andreas Muljadi middot Jos Pet middot JeV Whitty
Received 31 August 2007 Accepted 24 April 2008
Springer-Verlag 2008
Abstract Despite their large size and frequent occurrence
in near-shore tropical habitats little published information
is available on the movements and behaviors of the giant
manta ray Manta birostris and what factors inXuence visi-
tation patterns To examine the movements of manta rays in
the Komodo Marine Park Indonesia an acoustic array was
installed at up to seven sites in the park between 2000 and
2003 A total of 41 acoustic tags were deployed in three
separate deployments in 2000 2001 and 2002 Mantas were
recorded in the park for up to 526 days with an average
duration of 183 sect 136 days when mantas made from 3 to
303 individual visits to diVerent sites (median 58 visits)
There was a clear preference for three sites that comprised
over 90 of manta activity The most popular site (German
Flag) was oV the southern tip of Komodo Island in an area
with a high degree of bathymetric structure Examination of
the longest records suggests some site preference with 5 of
7 individuals spending greater than 90 of their time at the
location where they were tagged Using a general linear
model it was possible to examine the eVects of daytime
lunar phase aggregation site season and tidal phase on vis-
itation patterns The vast majority of visits were recorded
during daylight hours at all sites The strongest eVects of
both the lunar and tidal phase were apparent in the northern
sites with the most visits occurring when tidal intensity was
the greatest during full and new moons The strongest sea-
sonal pattern was observed in the south where no mantas
were recorded during the Wrst quarter in any year This
coincides with an increase in temperature and reduction of
productivity in this region associated with monsoonal
shifts The long-term Wdelity indicates that marine-pro-
tected areas centered around aggregation sites could help
protect this species from overexploitation
Introduction
The giant manta ray (Manta birostris DonndorV 1798) is a
monogeneric species in the subfamily Mobulinae (Family
Myliobatidae) that consists of the devil rays The giant
manta is the largest of all rays reaching a disc width of up to
67 m and 1400 kg weight (Last and Stevens 1994) Like
the largest whales and sharks manta rays are Wlter feeders
They and the other members of the subfamily funnel water
and prey into their mouths using their distinctive cephalic
lobes Prey is then Wltered from the water by modiWed gill
rakers The giant mantas are often observed feeding in
surge channels (Wilson et al 2001) on surface slicks or
near lights at night that act to concentrate prey Like the
largest Wlter feeding shark (the whale shark) manta rays
occur worldwide in tropical and subtropical waters
(Bigelow and Schroeder 1953 Last and Stevens 1994
Compagno 1999) While mantas are observed primarily in
Communicated by R J Thompson
H Dewar (amp)
National Oceanographic and Atmospheric Administration
Southwest Fisheries Science Center 8604 La Jolla Shores Dr
La Jolla CA 92037 USA
e-mail heididewarnoaagov
P Mous middot A Muljadi middot J Pet
The Nature Conservancy PO Box 80228
Jl Pengembak No 2 Sanur Denpasar 80235 Bali Indonesia
M Domeier
PXeger Institute of Environmental Research
901B Pier View Way Oceanside CA 92054 USA
J Whitty
Murdoch University South Street Murdoch WA 6150 Australia
A1
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LE TYPESET CP DISK
near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
58
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
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Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
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LE TYPESET CP DISK
aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
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327
328
329
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384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
581
582
583
584
585
586
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594
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611
612
613
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619
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621
622
623
624
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627
628
629
630
631
632
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635
636
637
638
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641
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(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
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and trade of whale sharks and manta rays in the Bohol Sea Phil-
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1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
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Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
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Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
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Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
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Dewar H (2002) Preliminary report manta ray harvest in Lamakera
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Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
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Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
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satellites with temperature data from tags on Wsh Fish Bull
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Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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ORIGINAL PAPER
Movements and site Wdelity of the giant manta ray
Manta birostris in the Komodo Marine Park Indonesia
Heidi Dewar middot Peter Mous middot Michael Domeier middot
Andreas Muljadi middot Jos Pet middot JeV Whitty
Received 31 August 2007 Accepted 24 April 2008
Springer-Verlag 2008
Abstract Despite their large size and frequent occurrence
in near-shore tropical habitats little published information
is available on the movements and behaviors of the giant
manta ray Manta birostris and what factors inXuence visi-
tation patterns To examine the movements of manta rays in
the Komodo Marine Park Indonesia an acoustic array was
installed at up to seven sites in the park between 2000 and
2003 A total of 41 acoustic tags were deployed in three
separate deployments in 2000 2001 and 2002 Mantas were
recorded in the park for up to 526 days with an average
duration of 183 sect 136 days when mantas made from 3 to
303 individual visits to diVerent sites (median 58 visits)
There was a clear preference for three sites that comprised
over 90 of manta activity The most popular site (German
Flag) was oV the southern tip of Komodo Island in an area
with a high degree of bathymetric structure Examination of
the longest records suggests some site preference with 5 of
7 individuals spending greater than 90 of their time at the
location where they were tagged Using a general linear
model it was possible to examine the eVects of daytime
lunar phase aggregation site season and tidal phase on vis-
itation patterns The vast majority of visits were recorded
during daylight hours at all sites The strongest eVects of
both the lunar and tidal phase were apparent in the northern
sites with the most visits occurring when tidal intensity was
the greatest during full and new moons The strongest sea-
sonal pattern was observed in the south where no mantas
were recorded during the Wrst quarter in any year This
coincides with an increase in temperature and reduction of
productivity in this region associated with monsoonal
shifts The long-term Wdelity indicates that marine-pro-
tected areas centered around aggregation sites could help
protect this species from overexploitation
Introduction
The giant manta ray (Manta birostris DonndorV 1798) is a
monogeneric species in the subfamily Mobulinae (Family
Myliobatidae) that consists of the devil rays The giant
manta is the largest of all rays reaching a disc width of up to
67 m and 1400 kg weight (Last and Stevens 1994) Like
the largest whales and sharks manta rays are Wlter feeders
They and the other members of the subfamily funnel water
and prey into their mouths using their distinctive cephalic
lobes Prey is then Wltered from the water by modiWed gill
rakers The giant mantas are often observed feeding in
surge channels (Wilson et al 2001) on surface slicks or
near lights at night that act to concentrate prey Like the
largest Wlter feeding shark (the whale shark) manta rays
occur worldwide in tropical and subtropical waters
(Bigelow and Schroeder 1953 Last and Stevens 1994
Compagno 1999) While mantas are observed primarily in
Communicated by R J Thompson
H Dewar (amp)
National Oceanographic and Atmospheric Administration
Southwest Fisheries Science Center 8604 La Jolla Shores Dr
La Jolla CA 92037 USA
e-mail heididewarnoaagov
P Mous middot A Muljadi middot J Pet
The Nature Conservancy PO Box 80228
Jl Pengembak No 2 Sanur Denpasar 80235 Bali Indonesia
M Domeier
PXeger Institute of Environmental Research
901B Pier View Way Oceanside CA 92054 USA
J Whitty
Murdoch University South Street Murdoch WA 6150 Australia
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LE TYPESET CP DISK
near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
58
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
158
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Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
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LE TYPESET CP DISK
aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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RR
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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LE TYPESET CP DISK
near-shore environments they are also reported at sea-
mounts and are even encountered far from shore in the open
sea
Some of the best information available on distribution
patterns within the mantasrsquo broad geographic range comes
from photo identiWcation studies that have recorded the
occurrence of photographically identiWed individuals over
time Based on this and other research local residence pat-
terns appear to be site dependent In certain regions the
same individual mantas are observed repeatedly over long
time periods (eg in Yap Hawaii and Bora Bora) whereas
in others (eg New Zealand Australia Mexico Africa
Ecuador and Southern Japan) their occurrence is seasonal
(Homma et al 1997 DuVy and Abbott 2003 S Fish per-
sonal communication P Ajhia personal communication
S Walker personal communication) When mantas are
sighted on multiple occasions they are often returning to
the same feeding and cleaning stations (Homma et al
1997) While these studies have provided important
insights into manta behavior they are limited temporally
and spatially to periods when divers or snorkelers are in the
water Also exactly what factors inXuence residence pat-
terns between and within diVerent regions is unknown
Although not the target of large-scale Wsheries giant
mantas are captured incidentally andor taken in regional
Wsheries through much of their range (Garcia and Hall
1997 Alava et al 2002 Dewar 2002 Romanov 2002 Fuj-
ita 2006 White et al 2006) Concerns about overexploita-
tion resulted in the listing of the giant manta as threatened
through part of its range by the IUCN World Conservation
Union (Marshall et al 2006) Although scientiWc studies
and exact population estimates are lacking a decline in
manta sightings has been noted in a number of locations
including Japan French Polynesia and Mexico (Homma
et al 1997 Marshall et al 2006) While elasmobranchs are
generally considered highly susceptible to over Wshing due
to their natural history (Musick 1999 Musick et al 2000)
mantas are likely even at greater risk given their very low
reproductive rates (one or two pups per year) generally
small population sizes and potentially limited distributions
(Marshall et al 2006)
An additional challenge to the management and conser-
vation of manta rays is the lack of published data on basic
life history information The lack of publications is due in
part to the fact that no industrial Wshery for mantas exists
and there has been little systematic collection of data The
vast majority of publications simply report on sightings in
regional species lists (Smith and Smith 1963 Santos et al
1997) Information on growth rates gestation period age at
sexual maturity and reproductive rates is scarce (Bigelow
and Schroeder 1953 White et al 2006) The results from
only one of the photo identiWcation studies mentioned
above have been published (Homma et al 1997)
We report on the movements of giant manta rays deter-
mined using an acoustic hydrophone array established in
the Komodo National Park Indonesia There are a number
of sites within the Komodo Marine Park where mantas are
regularly observed although it was not clear whether these
mantas were transient or resident and what factors inXu-
enced local patterns of occurrence There was considerable
interest in these questions for two reasons First local dive
operators were interested in developing manta-based eco-
tourism and it was important to obtain baseline informa-
tion on the local population as well as to identify visitation
patterns to maximize the success of the program Second in
two villages just east of Komodo (Lamalera and Lamakera)
there is a directed manta Wshery causing concern that the
mantas in the park may be impacted The objectives of this
study were to determine whether the mantas in the park
were resident and to identify temporal and spatial move-
ment patterns and their relation to environmental condi-
tions In addition to the value of this study to the local
manta population results may also provide insights into
patterns observed in other locations
Materials and methods
Tag deployments
The mantas were tagged with a V16-6H acoustic transmit-
ter (Vemco V16 Nova Scotia Canada) in a shark casing
Each tag transmitted a unique code allowing individual ani-
mals to be identiWed The tags were secured to the mantas
using large nylon darts that were attached to the tag using
300-lb test monoWlament line and stainless steal crimps
Two diVerent dart types were used White nylon darts with
two anchoring barbs (Prince and Goodyear 2006) were
used in the Wrst deployment Black nylon darts with eight
barbs (Domeier et al 2005) were used in the second and
third deployments The darts were inserted near the trailing
edge of the wing at the margin between the wing and the
axial musculature with a modiWed spear gun When the
mantas were tagged their size was estimated and the
behavior of the animal as well as that of the other mantas in
the area was noted
Acoustic array
The acoustic array consisted of Vemco VR2 omni-direc-
tional hydrophones The hydrophones were suspended at
depths from 8 to 25 m using plastic Wshing Xoats that were
secured to the bottom with large screws or sand bags
depending on the bottom substrate The tag ID code and
time were logged when tagged mantas were detected by the
hydrophones
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
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Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
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LE TYPESET CP DISK
aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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LE TYPESET CP DISK
describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
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491
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
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582
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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717
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719
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721
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723
724
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733
734
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736
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738
739
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741
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757
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759
760
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766
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769
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777
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
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Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
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1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
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Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
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Tont SA (1975) Deep scattering layers patterns in the PaciWc
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Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
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White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
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Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
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Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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Over the course of the study ten receivers were placed
in seven diVerent locations for varying periods of time
(Fig 1) including one hydrophone each at Padar Kecil
(PK) Mawan (MW) Loh Dasami (LD) and Tatawa Kecil
(TK) and two each at Karang Makasar (KM) Manta Alley
(MA) and German Flag (GF) (for color Wgure see online
version) Working from north to south TK is a small steep
isolated rocky island with substantial coral coverage KM is
located near a small sandy island away from distinctive
structures and is characterized by a very gradually sloping
coral rubble Weld with a few isolated coral heads MW is a
small island to the East of Komodo with a broad fringing
reef that is exposed to strong tidal currents PK is near an
isolated rocky island in the channel between Komodo and
Rinca Islands The sites at GF and MA are in the same gen-
eral area approximately 18 km apart at the south shore of
Komodo island where there are a series of rocky islands
and a rocky shoreline with a large degree of structure LD is
situated in a horseshoe-shaped bay in the South of Rinca
Island that has rocky shores and little reef formation All
locations were those where mantas had been observed by
the park rangers and The Nature Conservancy (TNC) staV
on multiple occasions
Range test
Range tests were conducted at GF A tag was placed in the
water and hung over the side of the vessel as the boat
drifted by the receiver with the tidal current The precise
time and location of the boat were documented using a
GPS These were then linked to the time-stamped data
recorded on the receiver
Fig 1 a Map showing Komodo
Island Indonesia and the loca-
tions of receivers around the Is-
land b The time a given
hydrophone was in the water
NKM
SKM
TK
MAW
PK
MA
MA2
GF
GF2
LD
a)
b)
158
159
160
161
162
163
164
165
166
167
168
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172
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Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
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LE TYPESET CP DISK
aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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LE TYPESET CP DISK
describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
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527
528
529
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546
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
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582
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
Au
tho
r P
ro
of
Mar Biol
123
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CO
RR
EC
TED
PR
OO
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Large 227 988 xxxx
Journal Article MS Code
Dispatch 30408 No of Pages 13
LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
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in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
791
792
793
794
795
796
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LE TYPESET CP DISK
Temperature records
Ambient water temperature was recorded at KM and MA
every 10 min using Onset Computer Tidbits (Onset
Bourne MA USA) These were secured to the hydropho-
nes and downloaded at the same time as the hydrophones
Additional temperature records were obtained from other
concurrent studies in the park using the same temperature
loggers
Data analysis
To characterize visitation patterns visits to a given site
were calculated from individual time-stamped data records
(termed hits) A hit was considered part of a given visit if it
occurred within in a 24-h period at the same receiver The
duration of each visit and the interval between visits was
calculated
To examine the eVects of location time of day time of
year moon phase and tides on manta occurrence a general-
ized linear model (GLM) (McCullagh and Nelder 1989)
was constructed using partial likelihood ratios for hypothe-
sis testing (SAS Institute Inc 1993) Applying a binomial
error and logit link function the GLM estimates the likeli-
hood that one or more tagged manta rays are recorded in
dependence of a range of variables (Table 1) This analysis
likelihood which varies between 0 and 1 is an indicator for
the presence of manta rays Analyses were restricted to
hydrophone recordings from the dominant north and south
aggregation areas (variable AA) north Komodo included
KM and south Komodo both GF and MA The other sites
were not included because hydrophone deployment was
less frequent and the number of hits per unit recording
eVort was far lower
For analyses recordings were categorized into calendar
months (variable MONTH) and into daytime (6 amndash6 pm)
and nighttime (6 pmndash6 am) (variable DAY) (these times
coincide with the approximate time of sunrise and sunset
through out the year) To examine the impact of both the
tidal intensity and phase two additional variables were
examined Moon phase (variable MOON) was included at
three qualitative levels lsquonewrsquo (lt10 illuminated) lsquohalfrsquo
(10ndash90 illuminated) and lsquofullrsquo (gt90 illuminated) The
illumination was obtained from the United States Naval
Observatory Astronomical Applications Department (http
aausnonavymildatadocsMoonPhase) Tidal phase (vari-
able TIDE) was categorized as lsquorisingrsquo lsquoslackrsquo or lsquofallingrsquo
Tidal height data were taken from tide tables for Bima (ca
80 km to the East of Komodo National Park) the nearest
location for which data are published The tidal height data
were oVset with +1 h for north Komodo and with +25 h for
south Komodo to align the table with observed current pat-
terns Because the eVects of MONTH DAY MOON and
TIDE may diVer between aggregation areas second order
interactions of these variables with AA were also included
The likelihood of recording a manta ray and number of
hits or visits will likely depend on the number of tags and
hydrophones in a particular area This was accounted for by
including sampling eVort (SEFF) in the GLM deWned as
the product of the number of active hydrophones at a partic-
ular site and the number of deployed tags In later analyses
SEFF was used to derive the number-of-hits per unit
sampling eVort (HUE analogous to catch-per-unit-eVort)
In the GLM however SEFF was included as an indepen-
dent variable along with the other independent variables
described above
The binomial dependent variable in the GLM here
abbreviated as PRSNT has a value of one if a manta ray
was detected (lsquopresentrsquo) and zero when no mantas were
detected (lsquoabsentrsquo) lsquoPresencersquo was evaluated per calendar
day (24 h) per level of each of the qualitative variables For
example if the hydrophones at MA recorded a series of hits
during rising tide at daytime but none during slack at
daytime then the dataset for that calendar day and that
Table 1 Summary of independent variables used in the GLM analysis
Independent
variable
Type Description Values
SEFF Continuous Sampling eVort a product
of the number of hydrophones and
the number of deployed tags
On average the two sites had 2 hydrophones
while 30 tags were deployed
SEFF averaged 54
(minimum 4 maximum 164)
AA Qualitative Aggregation area North Komodo South Komodo
MONTH Qualitative Calendar month 1ndash12 (JanuaryndashDecember)
DAY Qualitative IdentiWes recordings
made during daytime or nighttime
Daytime (6 amndash6 pm)
nighttime (6 pmndash6 am)
MOON Qualitative Illumination of the moon New (lt10 illuminated)
half (10ndash90 illuminated)
and full (gt90 illuminated)
TIDE Qualitative Daily variation in tidal currents Falling slack rising
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
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247
248
249
250
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aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
681
682
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686
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689
690
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692
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694
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728
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731
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734
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777
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tho
r P
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CO
RR
EC
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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aggregation area has one record with PRSNT = 1 DAY =
lsquodaytimersquo and TIDE = lsquorisingrsquo and one record with
PRSNT = 0 DAY = lsquodaytimersquo and TIDE = lsquoslackrsquo Both
records would have the same values for SEFF AA
MONTH and MOON The analysis was done with PROC
GENMOD in SAS 91 (SAS Institute Inc Cary NC)
Visual surveys
To assess the acoustic results and obtain additional infor-
mation on manta abundance a team of six observers made
61 trips to the three main sites (north and south Komodo
and PK) from May 2001 to June 2003 between 830 and
1500 The survey team slowly cruised each site by boat at
a maximum speed of ca 10 km hiexcl1counting mantas swim-
ming at and below the surface when visible When mantas
were observed the team reduced speed to better estimate the
group size It took 5ndash30 min to search each site and verify
the presence of mantas
To compare the acoustic and visual survey results hits
were aggregated over both north and south Komodo and
only daytime hits were used Numbers of hits per area per
day were corrected for SEFF The correlation between the
corrected number of hits and results from the visual surveys
was assessed through a non-parametric test for association
(Spearmanrsquos coeYcient of rank correlation Sokal and
Rohlf 1995)
Results
Tag deployments
A total of 41 tags were deployed during three deployment
periods eight in October 2000 15 in April 2001 and 18 in
May 2002 (Table 2) Deployments occurred at various sites
throughout the park near the location of the receivers The
average estimated wingspan of tagged mantas was 36 sect
08 m (range 18ndash5 m)
Receivers
Acoustic monitoring of manta rays was conducted from
October 2000 to June 2003 (Fig 1b) Due to a number of
problems coverage was not constant Problems included
receiver loss (likely to Wshermen) Xooding and battery
malfunction The main sites including GF (70) MA
(92) PK (78) and KM (86) or north Komodo were
covered for at least 70 of the study The more remote
sites had less coverage MW (51) TK (45) and LD
(26)
The range test at GF revealed that tags could be detected
only 10s of meters from the receiver The spacing of posi-
tions obtained with the GPS during the range test did not
allow for greater accuracy
Sites had diVering amounts of manta activity (Table 3)
with no mantas recorded at LD The highest number of
mantas was recorded at KM (n = 27) with only slightly
fewer at MA (n = 24) and GF (n = 24) 20 of these manta
were recorded at both GF and MA Fewer mantas were
Table 2 Summary of tag deployments including the location (Padar
Kecil = PK Mawan = MW Karang Makasar = KM Manta Alley =
MA German Flag = GF) and date of tagging the days between the tag-
ging date and when the manta was last recorded the total number of
visits and the days a manta was recorded
Six mantas (two from each deployment year) that were never recorded
are not included in the table
Tag Location Date Days Visits Days
2 KM 101600 101 8 7
4 KM 101600 208 26 21
5 KM 101600 162 9 8
3 KM 101700 178 4 4
7 GF 101900 266 28 21
8 GF 101900 98 5 5
9 KM 4201 250 71 66
10 KM 4301 31 24 21
13 GF 4301 151 132 86
14 GF 4301 32 13 10
15 MA 4301 311 53 51
16 GF 4301 48 3 3
17 KM 4301 207 40 36
18 MA 4301 519 165 96
19 MA 4301 222 168 109
20 KM 4301 526 152 131
21 GF 4301 161 60 44
22 GF 4301 198 208 139
23 GF 4301 54 12 9
25 GF 51902 362 57 44
1B PK 52002 202 63 41
2B GF 52002 216 207 125
31 GF 52002 215 159 120
32 GF 52002 116 111 81
33 GF 52002 367 132 92
34 PK 52002 216 170 126
3C MAW 52302 155 29 27
4B KM 52302 383 4 4
26 MA 52302 37 16 14
28 GF 52302 123 36 32
29 KM 52302 346 24 23
30 KM 52302 229 144 85
36 GF 52302 196 91 74
37 GF 52302 230 278 171
38 KM 52302 348 57 42
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
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281
282
283
284
285
286
287
288
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290
291
292
293
294
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296
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299
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
581
582
583
584
585
586
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
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and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
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Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
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Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
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satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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717
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719
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721
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723
724
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734
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736
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RR
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
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White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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LE TYPESET CP DISK
documented at PK (n = 14) TK (n = 3) and MAW (n = 7)
Despite the fact that a receiver was not installed at GF
until the second deployments it had the highest number
of raw and corrected hits and days with 43 of the cor-
rected days at this site The second most popular site was
KM (30 of corrected days) followed by MA (18) and
PK (7) MAW and TK had 1 or less of the total
corrected days
Tag activity
Tag activity is summarized in Table 2 and Fig 2 Of the 41
tags all but 6 were recorded by a receiver at least once Tag
transmitions were detected for periods up to 526 days
(average 183 sect 136) An individual manta made from 3 to
303 visits (median 58 visits) The median number of hits
per visit was 8 (maximum 209) and 23 of all visits con-
sisted of only one hit The median visit duration calculated
for each individual manta ranged from 8 min to 67 h with a
median over all mantas of 2 h The longest visits were close
to 24 h although this was uncommon and only 8 (04)
visits were longer than 20 h The number of days on which
hits were received for the individual mantas ranged from 3
to 171 (median 42) The percentage of days of a given
deployment on which hits were received from a given tag
ranged from 07 to 75 (median 206)
Manta movements
The visits for all the 35 mantas are shown in Fig 2 (for
color Wgure see online version) Given the variability and
complexity of patterns both within and across individuals
two approaches were taken to quantify patterns First the
timing of visits and movement between sites were quanti-
Wed Second the GLM was used to examine the inXuence
of environmental conditions comparing the north (KM) and
south (MA and GF) areas
An examination of successive visits reveals that it was
more common for mantas to visit the same site in subse-
quent visits than move to a diVerent site The majority of
subsequent visits (81) were at the same site Some mantas
were documented at the same site for many consecutive
days For example manta 20 missed only 6 out of 83 days
at KM and manta 22 missed only 7 days out of 113 at GF
When not on consecutive days the median time between
visits was 4 days with a maximum of 335 days (across all
tags the median value of the maximum time between con-
secutive visits was 44 days)
While some mantas visited only one site for weeks at a
time there was considerable movement among sites and
most mantas visited more than one site The most com-
mon movements were between the two closest sites oV
south Komodo MA and GF (n = 376) and 155 of these
occurred within a single day Movements between the
three main areas (PK north and south Komodo) occurred
less frequently (n = 145) Of the 21 animals with more
than 6 months of data and greater than 10 visits 19 visited
at least two areas and nine were recorded in all three areas
(PK north and south Komodo) The interval between vis-
its to diVerent areas increased with distance The average
time between south Komodo and PK (n = 45) was
66 days (min = 045 days) between north Komodo and
PK (n = 30) was 14 days (min = 06 days) and between
north and south Komodo (n = 47) was 25 days
(min = 07 days) Only two movements between the three
main areas (both between south Komodo and PK) were
documented on the same calendar day Note that the aver-
age time between areas is substantially longer than the
minimum values
To explore site preference seven mantas tagged at south
(n = 4 tag 15 18 25 33) and north (n = 3 tag 29 20
38) Komodo with more than 300 days of data and 25 visits
were examined A period of 300 days spans the seasonal
variations (see below) Five of the seven mantas spent on
average 97 (sect4) of the corrected days (days corrected
for SEFF) at the tagging location whereas the remaining
two spent 29 and 34 of the days at the tagging location
(Figs 2 3)
Table 3 Summary of the number of manta rays that visited each site the total and corrected hits and the total and corrected days and of total
corrected days on which mantas were recorded
The data for the two hydrophones at each of GF MA and KM were are combined in this table (Padar Kecil = PK Mawan = MW Karang
Makasar = KM Manta Alley = MA German Flag = GF Loh Dasami = LD Tatawa Kecil = TK)
Location Mantas Total hits Corrected hits Days mantas detected Corrected days Corrected days ()
GF 24 14975 384 958 268 043
KM 27 9265 314 521 188 030
MA 24 4729 124 419 112 018
PK 14 2941 72 185 45 007
MW 7 54 1 15 04 001
TK 3 152 4 4 01 000
LD 0 0 0 0 0 0
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
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LE TYPESET CP DISK
EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
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541
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LE TYPESET CP DISK
Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
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LE TYPESET CP DISK
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Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
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Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
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Sims DW (1999) Threshold foraging behaviour of basking sharks on
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EVects of place time daylight moon phase and tides
The GLM explained 36 of the total deviance using 34
degrees of freedom All main eVects and all interactions
with AA are summarized in Table 4 and were signiWcant
(P lt 001) The GLM that included second order interac-
tions was less parsimonious than the Wrst model (97 degrees
of freedom vs 34 degrees of freedom) and explained only
slightly more of the total deviance (38 vs 36) The more
parsimonious model comprising the main eVects and sec-
ond order interactions with AA was unlikely to have missed
major eVects Consequently this model was used to
Fig 2 The visitation patterns for all 35 mantas recorded by the acous-
tic array with the speciWc location of each visit color coded Data are
separated by the three deployment years For deployment 2 the arrows
indicate that for two tags additional recording were made after June
15th at the sites indicated
9-May-02 8-Jun-02 8-Jul-02 7-Aug-02 6-Sep-02 6-Oct-02 5-Nov-02 5-Dec-02 4-Jan-03 3-Feb-03 5-Mar-03 4-Apr-03 4-May-03
Ta
g
PK
MAW
TK
MA
GF
KM
251B2B313233343B4B26282930363738
22-Mar-2001 6-May-2001 20-Jun-2001 4-Aug-2001 18-Sep-2001 2-Nov-2001 17-Dec-2001 31-Jan-2002 17-Mar-2002 1-May-2002 15-Jun-2002
Ta
g
PK
TK
GF
KM
MA
ma
9
10
13
14
15
16
17
18
19
20
21
22
23
ma
06-Sep-00 20-Nov-00 03-Feb-01 19-Apr-01 03-Jul-01 16-Sep-01T
ag
KM
MA
GF
2
3
4
5
7
8
Fig 3 The corrected days at north Komodo (NK) and south Komodo
(SK) are shown for seven mantas with deployment durations of greater
than 300 days and more than 25 visits
0
10
20
30
40
50
60
70
80
90
100
15 18 25 33 20 29 38
Tag Number
T
ime
in
Are
a
NK
SK
Tagged at SK Tagged at NK Table 4 Results from the Generalized Linear Model (Type I analysis
SAS Institute Inc 1993)
Shown are the source of deviance (McCullagh and Nelder 1989) the
amount of deviance that remains after including the variable the Chi-
Square statistic for estimating signiWcance of the source and the P-val-
ue of Chi-Square
Source Deviance df Chi-Squared P
Intercept 10155
SEFF 9701 1 454 lt0001
AA 9668 1 33 lt0001
MONTH 9044 11 624 lt0001
AA pound MONTH 8081 11 963 lt0001
MOON 8015 2 66 lt0001
AA pound MOON 8000 2 15 00005
DAY 6568 1 1431 lt0001
AA pound DAY 6535 1 34 lt0001
TIDE 6517 2 17 00002
AA pound TIDE 6475 2 432 lt0001
385
386
387
388
389
390
391
392
393
394
395
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
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513
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521
522
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531
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540
541
542
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547
548
549
550
551
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555
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559
560
561
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564
565
566
567
568
569
570
571
572
573
574
575
576
577
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
581
582
583
584
585
586
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619
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621
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623
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629
630
631
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635
636
637
638
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641
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643
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645
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647
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649
650
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664
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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describe patterns standardized for SEFF = 60 The GLM
used 10512 records 1974 indicating presence of tagged
manta rays
The eVects of the interaction of AA and DAY were par-
ticularly strong (Table 4) Figure 4 shows hits in relation to
both time of day and the tidal cycle note that most hits are
recorded during the day in south Komodo even at diVerent
tidal phases Figure 5 shows the compiled hits per hour at
PK south and north Komodo over a 24-h period (note only
north and south Komodo were included in the GLM) The
number of hits gradually increased during the morning and
then decreased again prior to sunset with a peak shifted
slightly later at north Komodo The percent of nighttime
hits varied across locations and was highest at PK (north
Komodo = 1 south Komodo = 4 and PK = 22)
The second strongest interaction was between AA and
MONTH In the south the most visits occurred from April
to July and then declined until December after which no
mantas were recorded until March (Fig 6) In the north the
seasonal pattern appeared the reverse of that in the south
although animals were present in all months The move-
ments of some individuals suggested that mantas might
move from south to north late in the year In 2002 six man-
tas (25 2B 31 30 37 and 38) left southern Komodo in
November and December and arrived at northern Komodo
from 1 to 59 days later two additional manta rays (1B and
34) left PK for north Komodo around the same time These
mantas remained at the northern sites for up to 50 days
before leaving although one animal (38) was recorded
infrequently through May This pattern was not observed in
2001 indicating the potential for inter-annual diVerences
MOON and TIDES aVected visits at both north and
south Komodo but were strongest in the north (Fig 7) For
MOON at north Komodo manta ray abundance was higher
when currents are strongest during full and new moons
The GLM includes all visits over a 24-h period an exami-
nation of nighttime visits alone reveals a diVerent pattern
Around the full moon in south Komodo the number of
Fig 4 Solid line shows the tidal
depth over two diVerent 6-day
periods at south Komodo The
points indicate visits at either
German Flag or Manta Alley on
those days rounded to the nearest
hour The shaded bars indicate
the time between 6 pm and
6 am
Fig 5 Percent of total hits at
north Komodo (NK) south
Komodo (SK) and Padir Kecil
(PK) that occurred in a given
hour through out the day
0
005
01
015
02
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour of the Day
T
ota
l H
its
SK
PK
NK
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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LE TYPESET CP DISK
nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
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455
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457
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460
461
462
463
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469
470
471
472
473
474
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476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
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541
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
681
682
683
684
685
686
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688
689
690
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696
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704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
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721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
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739
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741
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749
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757
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766
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771
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774
775
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777
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RR
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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nighttime visits doubled from 10 (sect1) to 20 (sect1) of the
total visits No similar increase in nighttime visits was
observed at the other sites The eVect of TIDES was also
more pronounced in north with more visits during the rising
than the falling tide (Fig 7)
Visual surveys
During the visual surveys the number of manta rays
counted varied between 0 and 83 averaging 83 The cor-
rected number of visits from the acoustic receivers varied
between 0 and 36 per day averaging 024 The value of
Spearmanrsquos coeYcient comparing the number of corrected
hits and observed mantas was positive and signiWcant
(Spearmanrsquos coeYcient = 03 n = 61 P lt 005)
Temperature
Temperatures varied with season tidal cycles and across
sites The highest (328degC) and lowest (202degC) tempera-
tures were recorded in south Komodo which also had the
most notable seasonal pattern with maximum temperatures
observed in the Wrst quarter and the lowest values in the
third quarter of the year In the north the temperature range
was less from 239 to 294degC and the lowest temperatures
were recorded in both the Wrst and third quarter The tem-
peratures that the mantas encountered varied with location
(Fig 8) In the south 83 of hits occurred from 25 to 27degC
degrees (range 22 to 28degC) In the north 91 of hits
occurred from 26 to 28degC (range 24ndash29degC)
Discussion and conclusions
The acoustic array in the Komodo Marine Park Indonesia
enabled near continuous monitoring of manta activity at the
sites throughout the park where mantas were most com-
monly observed By collecting data over multiple years it
was possible to examine visitation patterns over various
time scales providing insights into the inXuence of time of
day tides lunar phase and season Here we present the
most comprehensive analysis of manta ray movements pub-
lished to date
Acoustic arrays have proven a valuable tool in this and
other studies (Klimley and Halloway 1999 Sundstrom
et al 2001 Voegeli et al 2001 Heupel and Simpfendorfer
2005) and are ideal for species that return to predictable
locations There are however limitations First it is not pos-
sible to determine where a tagged animal is when it is not
recorded or to distinguish between animals leaving the
study area and tag shedding Second the receiver range is
limited in near-shore habitats such as those frequented by
the mantas in the Komodo Marine Park where snapping
shrimp and bubbles associated with strong regional currents
limited the range of receivers (Voegeli et al 2001) Recep-
tion range was particularly low in the south nonetheless
these receivers collected the most data The high number of
detections at GF in particular may result from its location
between Komodo Island and a second small island that
serve as a bottle neck In addition foraging mantas were
observed to repeat the same route which would increase
the probability of detection While estimates of manta pres-
ence are undoubtedly conservative at all sites the agree-
Fig 6 Model results showing monthly variation in presence of tagged
manta rays in north Komodo (NK) and south Komodo (SK) Error bars
are 95 conWdence limits of the model estimates
0
02
04
06
08
1
1 2 3 4 5 6 7 8 9 10 11 12
Month
Pre
se
nc
e
NK
SK
Fig 7 Model results showing
the diVerence in presence of
tagged manta rays at north Kom-
odo (NK) and south Komodo
(SK) during a new moon half
moon and full moon recordings
and b falling slack and rising
tide These model estimates ap-
ply to the month November but
are representative of all months
Error bars are 95 conWdence
limits of the model estimates0
02
04
06
08
1
falling slack rising
Tide
NK
SK
b)
0
02
04
06
08
1
new half full
Moon phase
Pre
se
nce
NK
SK
a)
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
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455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
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518
519
520
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522
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524
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530
531
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537
538
539
540
541
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546
547
548
549
550
551
552
553
554
555
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
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and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
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in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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LE TYPESET CP DISK
ment between visual and acoustic surveys suggests that the
major trends were likely captured in this study
Manta rays in the park exhibited considerable site Wdelity
and demonstrated some individual preference for certain
areas Mantas returned to the same site almost daily for up to
3 months and visited sporadically for up to 2 years Mantas
with the longest records (gt300 days) appeared to prefer cer-
tain areas and were recorded most often near the tagging
location While most mantas with longer records visited at
least two areas movements between areas were somewhat
limited Thus while there is clearly exchange between sites
there may be residency patterns within the park
Site Wdelity has been reported in manta rays in other
locations as well Through photo identiWcation manta rays
have been documented to regularly return to speciWc feed-
ing or cleaning stations over long time periods An individ-
ual manta studied in the Yaeyama Islands Japan for
example was observed in the area for 15 years (Homma
et al 1997) Manta rays observed oV the big island of
Hawaii have been re-sighted over similarly long periods
(T Clark personal communication) In Bora Bora where
studies started more recently the same mantas have been
observed returning to the same cleaning stations for over
2 years (S Walker personal communication) In many
locations it is also common for individuals to be
documented only once (S Walker personal communica-
tion K Yano personal communication) raising the ques-
tion as to whether some mantas are transient This could
explain some of the shorter records observed in this study
although it is impossible to determine whether mantas left
the area or lost their tags
Teleosts and sharks return to predictable locations for a
range of reasons to spawn or reproduce (Domeier and
Colin 1997) using sites as landmarks along a migratory
route (Klimley and Halloway 1999 Klimley et al 1988) to
visit cleaning stations (Homma et al 1997) to take refuge
(Klimley and Nelson 1984 Holland et al 1993 Sims et al
2001) or take advantage of a predictable food source
(Klimley and Anderson 1996 Sims and Quayle 1998 Hey-
man et al 2001 Domeier and Nasby 2006 Graham et al
2006) Based on our observations the mantas returned to
the sites in the park for both feeding and cleaning It is also
possible however that these areas are important for repro-
duction (males and females are observed in the park) andor
provide important refuge from predators such as killer
whales and sharks which are known to attack manta rays
(Homma et al 1997)
While many of the manta rays in the park exhibited con-
siderable site Wdelity there are protracted periods when
they are not recorded at any receiver It is not clear whether
the animals are just outside the range of the array or have
left the park Similarly manta rays in Bora Bora are not
recorded for months at a time before returning although
with only Photo ID this pattern is diYcult to conWrm (S
Walker personal communication) Additional work using
pop-up satellite archival tags andor active telemetry
(Arnold and Dewar 2001 Voegeli et al 2001) would help
to resolve movements of mantas when they are not detected
by the receivers
Diurnal pattern
The examination of diurnal patterns shows the highest tag
activity at all sites during daylight hours The time of
arrival and departure coincides with the approximate time
of sunrise and sunset which changes little at these latitudes
One possible explanation for the diurnal pattern is that the
mantas are moving oVshore during the night possibly to
feed on the deep scattering layer (DSL) when it approaches
the surface (Tont 1975 Robinson and Gomez-Gutierrez
1998) This could help to explain the slight shift to later
hours at the northern site which is farther from deeper
water There is evidence for oV-shore movement and feed-
ing on the DSL from other areas Manta rays that were
actively tracked oV Japan moved oVshore at night and then
returned the following day (K Yano personal communica-
tion) While this may occur in other regions as well no pub-
lished accounts are available Another member of the same
family (Mobula japonica) feeds on crustaceans primarily at
night when they come to the surface (D A Croll et al
unpublished data) A number of other elasmobranchs
including scalloped hammerheads blacktip reef sharks and
gray reef sharks are also observed to aggregate in near
shore waters during the day and then disperse oVshore at
night (Klimley and Nelson 1984 Klimley et al 1988 Eco-
nomakis and Lobel 1998 Heupel and Simpfendorfer 2005)
Other possible explanations for the diurnal pattern are that
diVerent sites are preferred at night or that activity is lower
reducing the potential of detecting animals Clearly more
work is needed to explain the diurnal pattern
Fig 8 The percentage of hits at a given temperature are shown at both
north Komodo (NK) and south Komodo (SK) The temperature range
at each site is also indicated
0
5
10
15
20
25
30
35
40
45
20 21 22 23 24 25 26 27 28 29 30 31 32
Temperature (oC)
H
its
SK
NK
north temperature range
south temperature range
490
491
492
493
494
495
496
497
498
499
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503
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
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LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
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and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
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787
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LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
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Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
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Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
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1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
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White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
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in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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Foraging and tidal currents
While the acoustic tags do not indicate when animals are
feeding insights into foraging were gained through visual
observations and by examining visitation patterns Foraging
(when a mantarsquos cephalic lobes are unfurled and their
mouth is wide open) was common in the three main areas in
the park Mantas fed where prey appeared to be concen-
trated both in the water column where visibility was very
low and on surface slicks The concentration of prey is
considered to be critical for Wlter feeders likely due to the
energetic cost of feeding foraging is observed in both bask-
ing sharks (Sims 1999) and Wn whales (Clark et al 2000)
only above threshold prey density Although it has not been
directly measured prey density appears to be important for
mantas as well
There are a number of factors that likely enhance prey
densities in the Komodo Marine Park (1) The strong tidal
currents and complex bathymetry will enhance upwelling
and increase primary productivity (Field and Gordon 1996
Kinkade et al 1996) (2) The extreme tidal currents and
convoluted shorelines create complex secondary circula-
tions which results in convergence zones and tidal slicks
that act to accumulate zooplankton (Sugimoto 1975) The
site where the majority of visits were documented (GF) has
a high degree of structure (3) In addition tidally forced
internal waves and associated surface slicks transport
entrained material such as planktonic larvae towards the
shore likely bringing additional resources from oV-shore
waters (Shanks 1983) These processes will enhance the
biomass of available prey in the park beyond that produced
locally
Consistent with the apparent role of tidal currents in con-
centrating resources tidal phase and intensity impacted vis-
its More visits were documented at in north Komodo at the
rising tide (when currents move from the south to the north)
when the moon was new or full and tidal Xux is greatest
Tidal currents in this area shift 180 degrees with each tidal
change and can be up to 5 knots In contrast the inXuence
of tidal current and phase was less pronounced in south
Komodo In this region the variation in strength and direc-
tion of tidal currents is lower than in the north and therefore
one might expect a less pronounced eVect of lunar and tidal
phase on visitation patterns Furthermore the southern part
of the island has a more complex geography and bathyme-
try which may result in a more constant food supply that is
less dependent on tidal strength or speciWc direction
The concentration of prey associated with tidal currents
provides important forage for animals from diverse taxo-
nomic groups and impacts the temporal and spatial patterns
in feeding In a comparison of marine birds with diVerent
prey preferences the plankton feeder Ancient Murrelets
were most active when tidal Xow was the greatest (Holm
and Burger 2002) Dolphin foraging was most often
observed in association with tidal fronts in a narrow estua-
rine channel oV Scotland (Mendes et al 2002) The two
Wlter feeding sharks also forage in tidal currents Basking
sharks feed in near-shore regions where strong tidal Xows
aggregate zooplankton often near islands or headlands
(Sims and Quayle 1998) Whale sharks position themselves
to take advantage of tidal currents transporting material out
of the lagoon on Ningaloo reef Australia (Wilson et al
2001) Similar to these other species mantas appear to take
advantage of the increase in prey density associated with
the strong tidal currents around Komodo Island
A second factor that varies along with tidal intensity is
lunar illumination The increase in nighttime visits during
the full moon but not the new moon in south Komodo sug-
gests that high light levels and not tidal intensity are associ-
ated with the increase in visitation This shift could be
associated with an increase in foraging near-shore at higher
light levels or a decrease in oVshore foraging opportunities
During the full moon the DSL organisms remain deeper in
the water column (Blaxter 1974) and overall predation on
zooplankton has been shown to decrease as a result (Her-
naacutendez-Leoacuten et al 2001)
Season
A distinct seasonal pattern was identiWed in both north and
south Komodo Mantas were most abundant in the south
during the summer and in the north during the winter
While maximum abundances were reversed between the
two sites this pattern did not result solely from a shift from
one site to another although there is some suggestion at
least for the 2002 deployments that the some mantas moved
north after leaving south Komodo
While it is diYcult to identify the driving force behind
the seasonal change in manta abundance it is likely linked
to seasonal environmental patterns The shift in abundance
corresponds to the monsoonal shift in the Indo-PaciWc that
inXuences both temperature and productivity During the
Wrst quarter when no mantas were observed in south Kom-
odo the Indian Equatorial Counter Current and north mon-
soon are the driving processes (Tomczak and Godfrey
1994) At this time there is a reduction in the net Xow from
the PaciWc to the Indian Ocean that results in a drop in
productivity and an average 3degC increase in temperature
(Hahude and Gordon 1996) It was during this quarter that
temperatures here exceeded 30degC which is thought to be
the upper thermal limit for manta rays (no mantas were
recorded above 29degC in this study) Over the same period in
north Komodo waters are cool with poor visibility From
May to September when visitation in south Komodo is
high the South Equatorial Current and southeast monsoon
are both fully developed which maximizes westward Xow
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
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620
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628
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661
662
663
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(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
Au
tho
r P
ro
of
Mar Biol
123
UN
CO
RR
EC
TED
PR
OO
F
Large 227 988 xxxx
Journal Article MS Code
Dispatch 30408 No of Pages 13
LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
791
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Au
tho
r P
ro
of
Mar Biol
123
UN
CO
RR
EC
TED
PR
OO
F
Large 227 988 xxxx
Journal Article MS Code
Dispatch 30408 No of Pages 13
LE TYPESET CP DISK
(Tomczak and Godfrey 1994) and results in a drop in tem-
perature and large increase in productivity (Hahude and
Gordon 1996) During this phase the waters in the south
are cool and murky (visibility ca 5 m) and rich in plankton
Temperatures at in the north remained below 30degC and
mantas were seen here through out the year
As mentioned above seasonal shifts in manta distribu-
tions have been documented in a number of places and are
likely associated with temperature In locations such as
New Zealand mantas are observed primarily in the austral
summer (DuVy and Abbott 2003) In the Gulf of California
mantas are observed in the Boreal summer (P Ahjua per-
sonal communication) In the Maldives seasonal shifts are
thought to be associated with the local monsoons when
current directions reverse and mantas move from one side
of the Maldives to the other (Anderson 1996) In the Kom-
odo Marine Park the monsoons also impacted visitations
patterns although seasonality was site dependent This sug-
gests that subtle shifts in distributions may be associated
with seasonal patterns and that in a location as diverse as
Indonesia it may not be necessary to move very far to Wnd
suitable habitat
Management implications
The predictability of the spatial distribution of manta rays
has important consequences for conservation and tourism
management The information on patterns of occurrence
will assist dive operators in successfully planning manta
dives maximizing the potential of this ecotourism resource
For management and conservation the high site Wdelity and
ability to predict spatial patterns has two implications First
there is the potential for localized depletion or extirpation
once Wshers start exploiting an aggregation site On the
other hand site-speciWc protection or marine protected
areas based around aggregations sites should have a direct
positive eVect on local abundance
In Komodo speciWcally one of the key questions was
whether the boundaries of the park serve to protect the local
mantas from regional Wsheries Clearly the park encom-
passes a number of sites that are important for manta rays
and therefore the park provides some protection at least
during the day Of concern however is where the mantas
move when they are not within in the range of the receiver
Tagged mantas were not detected for long periods during
which they may have left the park One of the greatest
potential threats are the Wsheries in Lamalera and Lama-
kera which are approximately 400 km from the park
Manta ray migrations as far as 350 km have been docu-
mented (Homma et al 1997) and longer migrations are
likely possible raising the possibility that mantas could
move into this region In Lamakera it is estimated that
approximately 1000 mantas are taken in the Wshing season
from May through October (Dewar 2002) Mantas are also
taken in other locations throughout Indonesia although at
lower levels Additional information on the larger-scale
movements of mantas and the pattern of Wsheries is
required to better determine the management requirements
As indicated above mantas have the potential to be highly
susceptible to over Wshing and vigilance is warranted
Acknowledgments We thank the PXeger Foundation and The
Nature Conservancy for its support of this project The Weld research
could not have been conducted without the assistance of The Nature
Conservancy staV and Komodo Marine Park Rangers based on Flores
Indonesia who spent long hours on the water We also thank Russ
Vetter and Jason Larese for their valuable comments on the manu-
script The conclusions stated herein reXect the opinions of the authors
and not the National Oceanographic and Atmospheric Administration
Experiments were conducted in accordance with current laws in
Indonesia
References
Alava ERZ Dolumbaloacute ER Yaptinchay AA Trono RB (2002) Fishery
and trade of whale sharks and manta rays in the Bohol Sea Phil-
ippines In Fowler SL Reed TM Dipper FA (eds) Elasmobranch
Biodiversity Conservation and Management Proceedings of the
International Seminar and Workshop Sabah Malaysia July
1997 pp 132ndash148
Anderson C (1996) Manta tagging starts in the Maldives Shark News 76
Arnold G Dewar H (2001) Electronic tags in marine Wsheries research
a 30-year perspective In Seibert J Nielsen J (eds) Electronic tag-
ging and tracking in marine Wsheries Kluwer Dordrecht pp 7ndash64
Bigelow HB Schroeder WC (1953) Fishes of the Western North
Atlantic Part two SawWshes GuitarWshes Skates and Rays
Memoir Sears Foundation for Marine Research Number 1 Yale
University New Haven pp 481ndash515
Blaxter JHS (1974) The role of light in the vertical migration of Wshmdash
a review In Evans GC Bainbridge R Rackham O (eds) Light as
an ecological factor II Blackwell Oxford pp 189ndash210
Clark CW Croll DA Acevedo A Urban-Ramirez J (2000) Multi-mod-
al surveys of Wn whales in the Sea of Cortez Mexico J Acoust
Soc Am 1082539
Compagno LJV (1999) Checklist of living elasmobranchs In Hamlett
WC (ed) Sharks skates and rays the biology of elasmobranch
Wshes John Hopkins University Press Maryland pp 471ndash498
Dewar H (2002) Preliminary report manta ray harvest in Lamakera
Report to the World Wildlife Fund httpwwwtnc-seacmpaorg
downloadsalor20-20eBookpdf
Domeier ML Colin PL (1997) Tropical reef Wsh spawning aggrega-
tions deWned and reviewed Bull Mar Sci 60698ndash726
Domeier ML Kiefer D Nasby-Lucas N Wagschal A OrsquoBrien F
(2005) Tracking PaciWc blueWn tuna (Thunnus thynnis orientalis)
in the northeastern PaciWc with an automated algorithm that esti-
mates latitude by matching sea-surface-temperature data from
satellites with temperature data from tags on Wsh Fish Bull
103292ndash306
Domeier ML Nasby N (2006) Annual re-sightings of photographically
identiWed white sharks (Carcharodon carcharias) in an eastern
PaciWc aggregation site (Guadalupe Island Mexico) Mar Biol
doi101007s00227ndash006-0380-7
DuVy CAJ Abbott D (2003) Sightings of mobulid rays from northern
New Zealand with conWrmation of the occurrence of Manta bi-
rostris NZ J Mar Freshwat Res 37115ndash121
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
Au
tho
r P
ro
of
Mar Biol
123
UN
CO
RR
EC
TED
PR
OO
F
Large 227 988 xxxx
Journal Article MS Code
Dispatch 30408 No of Pages 13
LE TYPESET CP DISK
Economakis AE Lobel PS (1998) Aggregation behavior of the grey
reef shark Carcharhinus amblyrhynchos at Johnston Atoll Cen-
tral PaciWc Ocean Environ Biol Fishes 51129ndash139
Field AL Gordon AL (1996) Tidal mixing structures in the Indonesia
Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
face 3109ndash116
Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
1471239ndash1249
Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
sharks Rhincodon typus aggregate to feed on Wsh spawn in Bel-
ize Mar Ecol Prog Ser 215275ndash282
Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
ments and distribution of hammerhead shark pups on their natal
grounds Copeia 1993495ndash502
Holm KJ Burger AE (2002) Foraging behavior and resource partition-
ing by diving birds during winter in areas of strong tidal currents
Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
of the manta ray Manta birostris Walbaum in the Indo-PaciWc
In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
Conference Noumeacutea Soc Fr Ichthyol Paris pp 209ndash216
Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
soonal diVerences in phytoplankton biomass and production in
the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
Klimley AP Nelson DR (1984) Diel movement patterns of the scal-
loped hammerhead shark (Sphyrna lewini) in relation to El Bajo
Espiritu Santo a refuging central-position social system Behav
Ecol Sociobiol 1545ndash54
Klimley AP Butler SB Nelson DR Stull AT (1988) Diel movements
of scalloped hammerhead sharks Sphyrna lewini to and from a
seamount in the Gulf of California J Fish Biol 33751ndash761
Klimley AP Anderson S (1996) Residency patterns of white sharks at
the South Farallon Islands California In Klimley AP Ainly DG
(eds) Great white sharks the biology of Carcharodon carcharias
Academic Press San Diego pp 365ndash373
Klimley AP Halloway CF (1999) School Wdelity and homing syn-
chronicity of yellowWn tuna Thunnus albacares Mar Biol
133307ndash317
Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
IUCN Red List of Threatened Species httpwwwiucnredlistorg
McCullagh P Nelder JA (1989) Generalized linear models 2nd edn
Chapman Hall London
Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
239221ndash229
Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
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Large 227 988 xxxx
Journal Article MS Code
Dispatch 30408 No of Pages 13
LE TYPESET CP DISK
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Seas J Physic Oceanog 261924ndash1937
Fujita T (2006) A study of tuna bycatch using correspondence analysis
Masters Thesis University of California Los Angeles California
2006
Garcia MA Hall MA (1997) Spatial and seasonal distribution of by-
catch in the purse seine tuna Wshery in the eastern PaciWc Ocean
In Fisheries Bycatch Consequences and Management Dearborn
MI Alaska Sea Grant Program Report 97ndash02 pp 46ndash49
Graham RT Roberts CM Smart JCR (2006) Diving behaviour of
whale sharks in relation to a predictable food pulse J R Soc Inter-
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Hahude AG Gordon AL (1996) Thermocline stratiWcation within the
Indonesian Seas J Geophys Res 10112401ndash12409
Hernaacutendez-Leoacuten S Almeida C Yebra L Ariacutestegui J Fernaacutendez de
Puelles ML Garciacutea-Braun J (2001) Zooplankton abundance in
subtropical waters is there a lunar cycle Sci Mar 6559ndash64
Heupel MR Simpfendorfer CA (2005) Quantitative analysis of
aggregation behavior in juvenile blacktip sharks Mar Biol
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Heyman WD Graham RT Kjerfve B Johannes RE (2001) Whale
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Holland KN Wetherbee BM Peterson JD Lowe CG (1993) Move-
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Holm KJ Burger AE (2002) Foraging behavior and resource partition-
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Waterbirds 25312ndash325
Homma K Maruyama T Itoh T Ishihara H Uchida S (1997) Biology
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In Seacuteret B Sire JY (eds) Proceedings of the 5th Indo-PaciWc Fish
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Kinkade C Marra J Langdon C Knudson C Ilahude AG (1996) Mon-
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the Indonesian Seas tracing vertical mixing using temperature
Deep Sea Res I 44581ndash592
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of scalloped hammerhead sharks Sphyrna lewini to and from a
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Klimley AP Anderson S (1996) Residency patterns of white sharks at
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Klimley AP Halloway CF (1999) School Wdelity and homing syn-
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Last PR Stevens JD (1994) Sharks and rays of Australia CSIRO
Australia
Marshall A Ishihara H Dudley SFJ Clark TB Jorgensen S Smith
WD Bizzarro JJ (2006) Manta birostris In IUCN 2006 2006
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Mendes S Turrell WR Lutkebohle T Thompson PM (2002) InXuence
of the tidal cycle and a tidal intrusion front on the spatio-temporal
distribution of coastal bottlenose dolphins Mar Ecol Prog Ser
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Musick J A (1999) Ecology and conservation of long-lived marine ani-
mals Am Fish Soc Symp 231ndash10
Musick JA Burgess G Cailliet G Camhi M Fordham S (2000) Man-
agement of sharks and their relatives (Elasmobranchii) Fisheries
259ndash13
Prince ED Goodyear CP (2006) Hypoxia-based habitat compression
of tropical pelagic Wshes Fish Oceanogr 15451ndash464
Robinson CJ Gomez-Gutierrez J (1998) Daily vertical migration of
dense deep scattering layers related to the shelf-break area along
the northwest coast of Baja California Mexico J Plankton Res
201679ndash1697
Romanov EV (2002) Bycatch in the tuna purse-seine Wsheries of the
western Indian Ocean Fish Bull 10090ndash105
SAS Institute Inc (1993) SASSTAT Software The GENMOD Proce-
dure Release 609 SAS Technical Report Pndash243 SAS Institute
Inc Cary North Carolina
Santos RS Porteiro FM Barreiros JP (1997) Marine Wshes of the
Azores annotated checklist and bibliography Bull Univ Azores
Supplement 1 p 244
Shanks AL (1983) Surface slicks associated with tidally forced internal
waves may transport pelagic larvae of benthic invertebrates and
Wshes shoreward Mar Ecol Prog Ser 13311ndash315
Sims DW Quayle VA (1998) Selective foraging behaviour of basking
sharks on zooplankton in a small-scale front Nature 393460ndash464
Sims DW (1999) Threshold foraging behaviour of basking sharks on
zooplankton life on an energetic knife edge Proc R Soc Lond B
2661437ndash1443
Sims DW Nash JP Morritt D (2001) Movements and activity of
male and female dogWsh in a tidal sea lough alternative behav-
ioural strategies and apparent sexual segregation Mar Biol
1391165ndash1175
Smith JLB Smith MM (1963) The Wshes of Seychelles Rhodes
University Grahamstown
Sokal RR Rohlf FJ (1995) Biometry 3rd edn W H Freeman
New York
Sugimoto T (1975) EVects of boundary geometries on tidal currents
and tidal mixing J Oceanogr Soc Jpn 311ndash14
Sundstrom LF Gruber SH Clermont SM Correia JPS de Marignac
JRC Morrissey JF Lowrance CR Thomassen L Oliveira MT
(2001) Review of elasmobranch behavioral studies using ultra-
sonic telemetry with special reference to the lemon shark Negap-
rion brevirostris around Bimini Islands Bahamas Environ Biol
Fishes 60225ndash250
Tomczak M Godfrey JS (1994) Regional oceanography an introduc-
tion Permagon Tarrytown
Tont SA (1975) Deep scattering layers patterns in the PaciWc
CALCOFI Rep 18112ndash117
Voegeli FA Smale MJ Webber DM Andrade Y OrsquoDor RK (2001)
Ultrasonic telemetry tracking and automated monitoring tech-
nology for sharks Environ Biol Fishes 60267ndash281
White W Giles J Dharmadi Potter I (2006) Data on the bycatch Wsh-
ery and reproductive biology of mobulid rays (Myliobatiformes)
in Indonesia Fish Res 82 65ndash73
Wilson SG Taylor JG Pearce AF (2001) The seasonal aggregation of
whale sharks at Ningaloo Reef Western Australia currents
migrations and the El NintildeoSouthern Oscillation Environ Biol
Fishes 611ndash11
Yano K Sato F Takahashi T (1999) Observations of mating behavior
of the manta ray Manta birostris at the Ogasawara Islands
Japan Ichthyol Res 46289ndash296
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
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Au
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