ABUNDANCE AND DISTRIBUTION OF FRESHWATER EELS IN PANGI RIVER, MAITUM, SARANGANI PROVINCE

ARIANE SHANE M. VALDEZ

An Undergraduate Thesis Presented to the Faculty of the College of Fisheries

Mindanao State University General Santos City

In Partial Fulfillment of the Requirements for the Degree of Bachelor of Science in Fisheries

Major in Aquaculture

March 2015

APPROVAL SHEET

The thesis attached hereto entitled “Abundance and Distribution of

Freshwater Eels in Pangi River Maitum, Sarangani Province” prepared and

submitted by Ariane Shane M. Valdez in partial fulfilment of the requirements for

the degree Bachelor of Science in Fisheries major in Aquaculture is hereby

accepted.

PROF. RONALD P. SOMBERO PROF. GLENNVILLE A. CASTRENCE Member, Thesis Committee Member, Thesis Committee __________________________ _______________________________ Date Signed Date Signed

PROF. TERSA R. CASTILLO Adviser

_________________________

Date Signed

Accepted as partial fulfilment of the requirement for the degree of Bachelor of

Science in Fisheries major in Aquaculture

PROF. RONALD P. SOMBERO Dean, College of Fisheries

________________________

Date Signed

VITAE

The Researcher, Ariane Shane M. Valdez was born on May 27, 1995 in

Maitum Municipal Hospital, Maitum Sarangani Province. She is the second child

of Mr Allan A. Valdez and Mrs Ailen M. Valdez.

She spent her five elementary years in Edenton Mission College Inc., then

transferred to Pangi Elementary School, Maitum, Sarangani Province and

graduated in year 2007. In the same year, she continued her secondary

education at Malalag National High School, Maitum, Sarangani Province and

graduated as second honourable mention in the year 2011.

She took up Bachelor of Science in Fisheries major in Aquaculture at

Mindanao State University, General Santos City.

ACKNOWLEDGEMENT

The researcher would like to dedicate her work to those who shared their

support and guidance.

To her adviser, Prof. Tersa R. Castillo for the time and supervision, for the

significant ideas she had contributed for the success of the study.

To the members of the Thesis panel, Prof. Glennville A. Castrence and

Prof. Ronald P. Sombero, for their suggestions and contributions for the best

outcome of the study.

To Dr. Apolinario V. Yambot of the Central Luzon State University, Nueva

Ecija, for the knowledge he had shared and for his time and guidance throughout

the study.

The researcher would also like to express her gratitude to uncle illing, to

her friends, KH Family, classmates, CFC-Youth for Christ and MBH family for

giving her moral support.

All of these are impossible without her parents, Mr Allan A. Valdez and

Mrs Ailen M. Valdez, to his siblings Ezra and Dwin and her special someone,

Rein who had been her inspiration to finish this study.

And lastly, she is most grateful to the Almighty God, for He made all this

work in order. Thank you.

TABLE OF CONTENTS

Page

LIST OF FIGURES i

LIST OF TABLES ii

LIST OF APPENDICES iii

ABSTRACT iv

INTRODUCTION 1

REVIEW OF RELATED LITERATURE 3

MATERIALS AND METHODS 11

RESULTS AND DISCUSSION 19

CONCLUSION AND RECOMMENDATIONS 27

LITERATURE CITED 29

APPENDICES 33

i

LIST OF FIGURES

FIGURE PAGE

1 Map of Maitum, Sarangani Province 11

2 Sampling Area 12

3 Mouth of Pangi river during High Tide 12

4 Mouth of Pangi river at Low Tide showing the 3

stations and substations 13 5 Net Traps set at the Sampling Stations 14

6 Setting up the Net Trap 15

7 Monitoring the Trap and collection of trapped glass eels using scoop net (sigpaw) 15 8 Morphological characteristics of glass eels species showing the tail bud and caudal fin cutaneous pigmentation patterns; (a) Anguilla marmorata and/or Anguilla luzonensis (b) Anguilla bicolor pacifica (c) Anguilla japonica. 16

9 Net trap destroyed by waves and drifting woods at Station 1 21 10 Species of Anguillid eels collected from October 2014 to February 2015 23

ii

LIST OF TABLES

TABLE PAGE

1 Density of Anguillid eels Collected during 10 Sampling days from October 2014 to February 2015. 19

2 Species of Anguillid eels collected from Pangi River, Maitum, Sarangani Province from October 2014 to February 2015, their density and indices of abundance, frequency and dominance 22

3 Catch per Unit Effort 25

4 Temperature and salinity reading for 5 months of sampling from October 2014 to February 2015 26

iii

LIST OF APPENDICES

APPENDIX PAGE

1 Recording the collected eels 34

2 Sorting of the animals caught 34

3 The collected species of anguillid eels on Nov. 22, 2014 35

4 Monitoring of water temperature and salinity during sampling 35

5 Weighing of Samples 36

6 GPS and plastic measuring tape used in the study 36

7 Determining the samples using morphological characteristics 37

8 Preserved Samples and Ethanol used as preservative 37

9 Adult Anguilla marmorata trapped in Station 3 38

10 Tail bud of A. bicolor pacifica and A. marmorata 38

11 Other species trapped in the net traps during samplings (Freshwater crabs “Katang”, conger eel, and sea-snakes) 39

iv

ABSTRACT

VALDEZ, ARIANE SHANE M. Mindanao State University, General Santos City. March 2015. Abundance and Distribution of Freshwater Eels in Pangi River, Maitum, Sarangani Province.

Adviser: Prof. Tersa R. Castillo

A study on the abundance and distribution of freshwater eels was conducted in Pangi River, Maitum Sarangani Province. Three stations, 50 meters away from each other, were set starting at the mouth of the river with coordinates 06.02278° N, 124.52069° upstream. In every station are three substations; at the right side near the bank, at the center and at the left side of the river bank. The study was done for a period of 5 months starting from October 2014 to February 2015, where sampling was done every full moon and new moon of the month during the low tide and high tide fluctuations. Salinity and temperature were monitored during sampling.

The freshwater eels were identified using the morphological characteristics. Results showed that out of 18 species of anguillid eels identified, two species where collected in the area; the Anguilla marmorata and the Anguilla bicolor pacifica. The study further showed that Anguilla marmorata is most abundant with abundance index of 96.73%, frequency index of 100% and dominance index of 196.73%, while Anguilla bicolor pacifica had the abundance index of 3.26%, frequency index of 42.86% and dominance index of 46.12%. A total of 4,262 individuals had been collected for five (5) months of sampling, Freshwater eels were found abundant during new moon with a total of 4,249 individuals and only 13 individuals were collected during full moon. Catch per unit effort (CPUE) computed ranged from 0.075gm/hour to 500 gm/hour.

Temperature was monitored to be within the range of 22°C-28°C for the entire sampling period.

Further study is recommended to extend the stretch of sampling site beyond Station 3 to monitor migration pattern of freshwater eels upstream the river of Pangi, Maitum, Sarangani Province. Also to complete the one year data on the abundance and distribution of freshwater eels, a similar study shall be conducted for a period of one year.

Introduction

Eel is the common name for any fish of the 10 families constituting the

Order Anguilliformes. It is characterized by a long snakelike body covered with

minute scales embedded in the skin. Eels lack the hind parts of fins, adapting

them for wriggling in the mud and through the crevices of reefs and rocky stones.

The catadromous eels of the genus Anguilla appear to have originated in

the tropical regions of the Pacific Ocean, where the greatest number of species is

found (Tsukamoto & Aoyama 1998).

The fishing for freshwater eels, along with environmental pollution

and other human impacts, have all contributed to a significant decline in eel

numbers over the last 25–30 years. Total volume of glass eels collected on an

annual basis is around 150 tonnes which satisfies the current aquaculture needs

of approximately 100 tonnes/year with the excess going to human consumption

in Spain. Many people are involved in the eel collection, transportation and

distribution, from glass eel fishers to the eel farmer and processor (Nielsen and

Prouzet, 2008.)

In the Philippines, freshwater eels have different populations scattered in

various regions of the country in which they are considered important food fish

especially to the indigenous people (Jamandre et al 2007). There has been no

documented on the evolutionary history and phylogenetic studies of the eels in

the country and by traditional molecular methods, where those fishes are quite

2

abundant and geographically near to their spawning ground (Jamandre et al

2007). Knowledge and background of the natural life history and specification are

the basis for sound fishery management or development of aquaculture industry

of eels.

The present study provides baseline information on the abundance and

distribution of the freshwater eels at Pangi River, Maitum, Sarangani Province.

This serves as basis for action plan of the Local and National Government Units

for protection and conservation of freshwater eels in the area.

Review of Related Literature

Anguillidae is a family of fishes that composes many of the freshwater

eels. There are about 18 species of anguillid eels in the world. Most of them are

tropical species residing in the Indo-Pacific region (Tesch 2003). According to

Ege (1939), 25,265 were identified from available Anguilla specimens collected

worldwide by systematic analyses. Castle and Williamson (1974) suggested that

A. ancestralis specimens was a synonym of A. celebesensis, and therefore

reduced the genus to 15 species. Based on the report of Ege (1939) on the 12

morphological characters, a phylogenetic synopsis for the genus Anguilla was

constructed. Species with a short dorsal fin and those without variegated

markings were thought to have been derived from a common ancestor.

The anguillid eels are an ancient teleost taxon and besides occupying an

important place in the diet of many human populations, they possess very

unusual features in their multistage catadromous life cycle and different life

stages. Key aspects still rank among the great unsolved mysteries of biology, the

most obvious being that there is still no direct observational evidence on the

oceanic migrations of anguillid silver eels to their spawning grounds, spawning

itself nor the return journeys of larvae to growth areas in continental waters

(Tesch, 2003). Even then, the individual and population biology of the larvae is

also a mystery.

4

Freshwater eels are elongated with tube like, snaked-shaped bodies. They

have a large, pointed heads and their dorsal fins are usually continuous with their

caudal fins and anal fins, to form a fringe lining at the posterior end of the body.

They have small pectoral fins to help them propel and navigate along river

bottoms. These species are aquatic breathers but also possess cutaneous mode

of respiration. According to Helfman (1987), males tend to be found in lower

parts of estuaries, and females much farther away from spawning grounds.

Oliveria (1999) stated that females require lower densities and they are much

larger than the male eels.

In their natural habitat eels are top predators that feed during the night on

small fish, amphibians, crustaceans, echinoderms, insect larvae, etc. Once

attaining maturity at an age of 5-15 years, the female eels stop eating, change

body shape and colour, develop the reproductive organs and migrate to the sea.

Males become mature before the females. (Herwaarden 2003).

Freshwater eels of the Genus Anguilla are catadromous fishes that

migrate between freshwater and marine environments with their spawning areas

being offshore in the ocean (Tesch 1997, 2003). The catadromous life history of

anguillids is unique because they have a relatively long larval development as a

transparent leaf-like larva (leptocephalus) that is peculiar larval form of

elopomorph fishes and is thought to be highly adapted to a planktonic life in the

open ocean (Smith 1989; Pfeiler 1999; Miller and Tsukamoto 2004). The eels

5

have a multi-stage life cycle and spawn in the open ocean. Anguillid eels spawn

in the open ocean and eggs hatch into a larval form called leptocephali. The

leptocephali metamorphosize into the glass eel stage while drifting with the

currents towards continental waters. Glass eels typically begin to show

pigmentation as they arrived in continental waters where they are called elvers.

Once fully pigmented, they are termed yellow eels and will spend the majority of

their lives feeding and growing across range habitats. Upon maturity, a silvering

of the skin prepares the “silver eel” for the oceanic migration back to their

spawning area (Tesch 2003).

After spawning, their leaf-like larvae called leptocephali, drift with the

oceanic currents towards their continental growth habitat where they

metamorphose to glass eels in the continental growth habitat and develop to

elvers when they reach the estuary. The elvers eventually settle in the brackish

coastal water, estuaries and rivers to grow into yellow eels and go back to the

oceanic spawning ground to reproduce and die (Tseng 2001;Tzeng, 2004).

The catadromous life history of spawning in the ocean and rearing in fresh

water is commonly assigned to anguillid eels which are often termed “freshwater

eels”. However, catadromy is a misleading descriptor for this genus because

growth is not restricted to fresh water. Residency in fresh water is not obligatory

for European eels, A. anguilla (Limburg, et al 2003), Japanese eels (A. japonica)

6

(Tsukamoto and Arai 2001), short finned eels (A. australis) (Arai et al. 2004) or

American eels (A. rostrata) (Morrisson et al. 2003).

Light intensity appears to have a strong effect on the inshore migration

mechanisms of glass eels entering the mouth of the river as has been observed

in previous studies with other species. Usually fish migrate upstream mainly

during twilight and dark periods (Jonsson 1991), Deelder (1952) found that

Anguilla anguilla glass eels migrated during darkness. They started to ascend

into freshwater at the beginning of sunset, with abundance gradually increasing

during the night up to a peak around midnight and then rapidly decreasing just

before sunrise.

Most species of aquatic animals including eels are utilized for human

consumption. Fresh eels are the primary food during September and October in

European countries. Eels are dried when they are abundant, providing

sustenance from November through January. Smoked eels, being lightweight

and highly nutritious (Casselman 2003), were commonly used as traveling food

(Junker-Anderson 1988). Indigenous peoples often give eels as gifts to early

European travellers or used them in trade (Beauchamp 1916).

The aquaculture production of Anguillid eels has shown a staggering

growth in the last few decades. Global eel production in 2001 was estimated by

FAO at 231,000 MT and is predominantly concentrated in the Far East (China

155.800 MT, Taiwan 34.000 MT, Japan 23,100, Malaysia 2,400 MT, and Korea

7

2,600 MT) and a few countries in Europe (10,200 MT). In Europe, the only

species cultured is European eel (Anguilla anguilla), whereas in Asia, the

Japanese eel (A. japonica) is the main species cultured. However, due to

shortages of seed fish of the Japanese eel in its native range, a considerable

amount (50,000 MT) of European eel is produced in this area as well.

(Herwaarden, 2003).

According to Jamandre et al (2007), in the Philippines, freshwater eels

have different natural populations scattered throughout the whole country. The

Philippine archipelago accommodates four of the total 18 species of eel found

around the world. The most widespread species is A. marmorata which can be

found throughout the archipelago. Anguilla bicolor pacifica inhabits the Southern

part of Luzon, the Visayas and Mindanao whereas A. celebensis can be found in

western half of the archipelago. The three above mentioned species are known

as tropical eels. The Japanese eel (A. japonica) is a species from the temperate

regions that migrate in low percentage in the Northern part of Luzon. It is an

important food fish for many of the indigenous people that live along the swamps

and rivers. Some regard this group of fish as mystical because of its long life and

largeness in size. However, there has been no documentation of the basic

biology of eels in the Philippines, where these fishes are quite abundant and

geographically near to their spawning ground.

8

The Philippine archipelago lies within the Indo-Pacific region, near the

major spawning grounds of both the tropical eels and the temperate eel (Anguilla

japonica) in the western waters of the Marianas Islands. With the influence of the

North Equatorial Current and its archipelagic nature, many freshwater eels thrive

and succeed in building separate populations in the Philippines, especially in the

large rivers and estuarine areas of Northern Luzon. It has been known that the

Indo-Pacific region was the origin of the speciation of the freshwater eels of the

genus Anguilla (Aoyama & Tsukamoto, 1997; Lin et al., 2001). The ancestors of

both temperate and tropical eels originated from the Indo-Pacific region,

particularly in the archipelagic area of Indonesia, Malaysia and the Philippines.

The Philippines has been identified as an increasingly important source of

Anguilla spp. in recent years. Owing to the dramatic increase in exploitation and

price of glass eels in the Philippines in 2011 and 2012, in May 2012 the

Philippine Bureau of Fisheries and Aquatic Resources (BFAR) brought in a

precautionary measure banning the export of juvenile eels ≤15cm in length

(Crook 2014).

In Asia, the Philippines in particular were identified as an important

source, being the home to at least five different Anguilla species: A. bicolor, A.

marmorata, A. japonica, A. celebesensis and A. luzonensis, the latter only

described in 2009 (Watanabe et al., 2009). Due to its similar texture and taste, if

A. japonica is not available to the consumer, A. bicolor is the preferred second

9

option and therefore in particular demand (Anon, 2013; Anon, 2014a). All five

species have recently been assessed against the IUCN Red List criteria, and due

to concerns that a variety of threats, including over‐exploitation, are causing

declines in their populations, A. japonica was rated as Endangered and A.

bicolor, A. celebesensis and A. luzonensis as Near Threatened (A. marmorata

was rated as Least Concern) (Jacoby and Gollock, 2014).

There is a related study conducted in Luzon by Jamandre et al. (2007)

where they used to identify the eel species collected in the Philippines and to

validate their identity and determine their phylogenetic relationship by analyzing

the 16S rRNA and cytochrome b genes of mitochondrial DNA (mtDNA). A total of

24 freshwater eels were collected from the Cagayan River system and Chico

River. Morphological characteristics of the eel, such as the presence of mottles

on the skin and length of fins were used to establish a basis for preliminary

identification of the species. The morphometric measurements gathered were as

follows: total length (TL), head length (H), pre-dorsal fin length (PD), pre-anal fin

length (PA), distance between verticals from origin of dorsal fin to anus (AD) and

percent (%) values of AD in proportion to TL.

The present study is a survey of freshwater eels in Pangi River, located at

Maitum, Sarangani Province. The headwater of this river originates from Mount

Busa, Datal Mahe or Datal Aga of Sarangani Province. The downstream portion

is located at the foot of the Pangi Bridge, Maitum Sarangani Province,

10

approximately 1-2 km. from the mouth of the river with coordinates N 06° 02’13.3,

E 124° 31’ 56.0”. Its upstream portion is located at NIA Dam, New La Union,

Maitum, Sarangani Province with coordinates N 06° 04’17.8” E 124° 34”39.8”.

Pangi River is the boundary between the Municipality of Maitum and the

Municipality of Kiamba, Sarangani Province. It is primarily used for irrigation as

well as for bathing, washing and drinking of both the residents and their

domesticated animals, ( Rellon, 2013). Pangi river empties into Sarangani Bay.

Another study also on the Poigar river was conducted by Sugeha (2001)

on inshore migration of the tropical eels Anguilla spp. recruiting to the Poigar

River estuary on north Sulawesi Island. They collected 32,836 glass eels in the

Poigar River estuary on north Sulawesi Island, Indonesia, in monthly collections

from 1997 to 1999. They found 3 species, A. celebesensis, A. marmorata, and A.

bicolor pacifica. A. marmorata was the second most abundant species next to A.

celebensis and comprised 23.8, 18.8, and 17.7% of the yearly catches,

respectively, and reached peaks in abundance during June in 1997 and 1998,

and during January in 1999. A. bicolor pacifica comprised only 2.7, 1.7, and 0.3%

of the yearly catches, respectively, with peak catches in June in 1997, in January

in 1998, and in January and February in 1999.

MATERIALS AND METHODS

Sampling Area and Sampling Stations

The study was conducted at Pangi River at Brgy. Pangi, Maitum

Sarangani Province (Figs 1 and 2). The sampling stations were set at the river

from its mouth upstream, each sampling station was subdivided into three (3)

substations, where two (2) are designated at both sides and one (1) substation at

the center (Figs 3 and 4). The study was done for five (5) months from October

2014 to February 2015.

Figure 1. Map of Maitum, Sarangani Province

12

Figure 2. Sampling Area

Figure 3. Mouth of Pangi river during high tide

Maitum

Kiamba

Stretch of

Pangi River

Mouth of the

river

13

Figure 4. Mouth of Pangi river at low tide showing the 3 stations and substations Sampling stations were set from the mouth of the river going upstream

with Station 1 at coordinates 06.02278 °N, 124.52069 °E at the mouth of the

river, expanding from 31 meters at low tide to 100 meters up at high tide. Station

2 was set 50 meters away from Station 1, at coordinates 06.02435 °N,

124.52196 °E while Station 3 was 50 meters away from Station 2 at coordinates

06.02479 °N, 124.52287 °E. Every sampling station was further subdivided into 3

substations across the width of the river where the station was set. Substations 1

are set at the right side of the river bank, while at the opposite left side are

Substations 3 and at the middle is designated as Substation 2 (Fig. 4)

14

Sampling Methods and Sample Collection

Collection of samples was done by setting the net traps (as collecting

gears) at the three (3) stations (Fig. 5). This is made of 8 meters fine mesh net as

wings, ropes for holding, bamboo sticks to form support of the nets, and rocks as

sinkers. A set of three net traps were installed in the three substations to

intercept as many as possible eels over a wide area. The net traps were set in

the afternoon in time with the incoming high tide, for four (4) hours, after which,

the nets were checked for presence of trapped glass eels, which were collected

using the scoop net (“sigpaw”) (Figs 6 and 7). Sampling was done every full

moon and new moon of the month in time with the tidal fluctuation to facilitate

collection of freshwater eels. The collected samples of anguillid eels were fixed in

95% ethanol immediately after weighing and counting to serve as voucher

specimen.

Figure 5. Net traps set at the Sampling Stations

15

Figure 6. Setting up the Net Traps

Figure 7. Monitoring the trap and collection of trapped glass eels using scoop net (sigpaw)

16

Data Collection

The information that were noted and gathered during sampling was the

following:

1. Date and Time of sampling

2. Length of fishing period (from setting until retrieval of the net traps)

3. Water parameters like temperature and salinity

4. Biomass of animals caught

5. Morphometric measurements of elvers and adults that were collected.

The eels collected were identified through its morphological

characteristics, (Fig. 8) particularly through the tail bud and caudal fin using the

guide provided by Yambot (2007).

Figure 8. Morphological characteristics of glass eels species showing the tail bud and caudal fin cutaneous pigmentation patterns; (a) Anguilla marmorata and/or Anguilla luzonensis (b) Anguilla bicolor pacifica (c) Anguilla japonica.

a c b

17

From the data, collected the following formulas were used to compute for

the following biological informations:

1. Catch per unit effort (CPUE)

The Catch per unit effort (CPUE) provides information on biomass of

animals caught and for a particular fishing duration.

(Total weight of catch) CPUE (kg/hour) = ------------------------------------------------

(No. of hours fishing)

2. Abundance Index (AI)

Abundance Index (AI) describes the most abundant species in relation to

all species caught or gathered.

Total no. of particular species Abundance Index= ------------------------------------------ x 100 Total no. of all species

3. Frequency Index (FI)

Frequency Index (FI) describes the number of times a particular species

appears in all the sampling conducted.

18

No. of sampling the particular species found Frequency Index = ------------------------------------------------------------ x 100 Total no. of sampling

4. Dominance Index (DI)

Dominance Index (DI) describes the sum of the Abundance and

Frequency Indices.

Dominance Index= Abundance Index + Frequency Index

Water parameters Monitoring and Observation of Climatic Conditions

Salinity and temperature readings were taken during sampling using

refractometer and thermometer, respectively. General Climate conditions were

observed and noted every sampling period.

RESULTS AND DISCUSSION

Density of anguillid eels collected during the sampling period from October

2014 to February 2015 are presented in Table 1.

Table 1. Density of Anguillid eels Collected during 10 Sampling days from

October 2014 to February 2015.

Sampling Collected Eels Species Collected Condition of

the Area

During

sampling

Day

Date

Lunar Phase

No.

(pcs)

Weight

(g)

A.

marmorata

A. bicolor

pacifica

1 October

9 Full Moon 1 2,000 1 0 Cloudy, windy

stormy

2 Oct. 29 New

Moon

0 0 0 0 Windy,Stormy,

Heavy rain

3 Nov. 7 Full Moon 10 1.5 10 0 Rainy, dark

4 Nov. 22 New

Moon

3,560 534 3,453 107 Cloudy,

rainy, dark

5 Dec. 6 Full Moon 0 0 0 0 Stormy,

flood

6 Dec. 22 New

Moon

620 93 592 28 Cloudy,

rainy

7 Jan. 5 Full Moon 0 0 0 0 Rainy, Dark

8 Jan. 20 New

Moon

18 2.7 18 0 Rainy, Dark

9 Feb. 4 Full Moon 2 0.3 2 0 Rainy,Dark

10 Feb. 19 New

Moon

51 7.6 47 4 Rainy,Dark

20

For the whole duration of the sampling, from October 2014 to February

2015, the large catch of freshwater eels were during the new moon, with the

largest catch on November 22, 2014 with 3,560 pieces followed by 620 pcs on

December 22, 2014, 51 pcs on February 19, 2015 and 18 pcs on January 20,

2015. During the full moon, very minimal catch of Anguillid eels, with the largest

catch on November 7, 2014 with 10 pcs and 2 pcs on February 4, 2015 and only

1 adult eel (2,000g or 2.0kg) trapped in Station 3 upstream on October 9, 2014.

The rest of the sampling period had no catch for reason like occurrence of

storms, heavy rains and strong waves and winds which practically destroyed the

net traps.

Most of the trapped animals were glass eels in Station 2, particularly in its

Substation 1 and few in Substations 2 and 3. This portion was observed to have

less current so that glass eels are not easily drifted. Stronger currents in

Substation 2 of the 3 Stations caused the drifting of net traps set so that these

are often times destroyed. No eels were gathered in Station 1 designated at the

mouth of the river, since this area is often times exposed to strong winds and

waves and nets traps were overrun by drifting woods especially during stormy

days with heavy rain (Fig. 9).

21

Figure 9. Net trap destroyed by waves and drifting woods at Station 1

As gathered from informal interview with the fishermen-collectors in the

area and with those from identified collecting areas like in Buayan River, glass

eels are usually trapped in large number in river banks where water currents are

already dissipated in the area due to some crevices and irregular coastline

margins which obstruct water flow thus slow down water currents and provided

refuge to the animals.

According to Tzeng (1985) eel is more abundant during new moon phase

than full moon phase since, freshwater eels are more seen during dark hours

such as new moon and glass eels prefer to migrate during these times.

There are two (2) types of substrates observed in the area: sandy and

rocky. The mouth of the river in Station 1 had sandy bottom while Stations 2 and

3 had rocky bottom.

Station 3 located 100 meters from the mouth of the river upstream is

already freshwater (0 ppt) with its bottom characterized by the rocks and strong

22

currents so that this made setting the net traps difficult. For the whole sampling

period, only 1 adult eel (2.0 kg) was collected in its substation 1 (Appendix Figure

9).

As the eels migrate upstream, it undergoes metamorphosis as affected by

salinity and age. Animals that reach the freshwater environment are usually fully

pigmented and called as “yellow eels” where they spend majority of their lives

feeding and growing across range habitats (Tesch 2003). Elvers and yellow eels

are bigger enough to elude from the traps. This could be the reason for

particularly no catch in Station 3.

Table 2 presents the species of Anguillid eels, their density and indices of

abundance, frequency and dominance for the five (5) month sampling.

Table 2. Species of Anguillid eels collected from Pangi River, Maitum, Sarangani Province from October 2014 to February 2015, their density and indices of abundance, frequency and dominance.

Species Collected

Density (pcs)

Indices

Abundance

(%)

Frequency

(%)

Dominance

(%)

Anguilla marmorata 4, 123 96.73 100.00 196.73

Anguilla bicolor

pacifica

139 3.26 42.86 46.12

Total 4,262

23

There were two species of Anguillid eels sampled from October 2014 to

February 2015. These are the Anguilla marmorata and Anguilla bicolor pacifica.

Of the total sample of 4,262 individuals collected for the whole sampling

period, A. marmorata was the most abundant anguillid eels in all the samplings

with a total of 4,123 individuals with an abundance index of 96.73%. It is likewise,

the most frequently occurring species (Fig. 10). In fact, it appears in all samplings

conducted, thus resulted to 100% frequency index. Being the most abundant

species and frequently occurring species, it is also the most dominant species

(Dominance Index of 196.73%). On the other hand, only 139 pcs of A. bicolor

pacifica were collected with abundance index of 3.26%, frequency index of

42.86% and dominance index of 46.12%.

Figure 10. Species of Anguillid eels collected from October 2014 to February 2015

24

Arai (2011) reported that catadromous eels, Anguilla marmorata, A.

bicolor pacifica are widely distributed in Asian countries including Vietnam.

Anguilla marmorata is more quietly abundant with the abundance index of 80%

while A. bicolor pacifica had an abundance index of 50%.

Sugeha (2001) described the inshore migration of the tropical eels,

Anguilla spp., recruiting to the Poigar River estuary on north Sulawesi Island. He

collected a total of 32,836 glass eels in Poigar River on North Sulawesi Island,

Indonesia, in monthly collections from 1997 to 1999. The samples were identified

using morphological characters, where three (3) species, A. celebensis, A.

marmorata and A. bicolor pacifica, were found each year in fluctuating

abundances. A. celebensis was the most abundant species. This is relatively all

three (3) years with peaks during June 1997 and 1998, and during September in

1999. A. marmorata was the second most abundant species which reached

peaks in abundance during June 1997 and 1998 and January 1999. A. bicolor

pacifica comprised smaller yearly catches, with peak in June 1997, in January

1998 and January and February in 1999. A. celebensis and A. marmorata were

collected almost throughout the year in 1997, 1998, and 1999, suggesting that in

contrast to the temperate eels that and recruited during half the year from winter

to spring, these tropical eels were recruited to some degree throughout the year.

Glass eels were more abundant during new moon sampling periods

25

Catch per unit effort (CPUE) was computed based on the corresponding

catch every sampling after four (4) hours of setting the net traps. The Highest

CPUE of 133.5 g/hour was computed in the 4th sampling on Nov. 22, 2014 during

the new moon, followed by 23.25 g/hour on the 6th sampling on Dec. 22, 2014

then on the 10th sampling on Feb. 19, 2015 with the CPUE of 1.99 gm/hour, and

CPUE of 0.675 gm/hour, 0.375 gm/hour and 0.0759 gm/hour, on the 8th, 3rd and

9th samplings, respectively (Table 3). However, CPUE of 500 gm/hour was

computed in the 1st sampling where only 1 adult individual trapped in Station 3.

During the sampling days, temperature was read, which ranged from 22

°C to 28 °C. Temperature readings were low during samplings in October 2014,

until January 2015 with range from 22 °C to to 25 °C, then increased in the

month of February 2015 ranging 26 °C to 28 °C. Salinity levels were read with a

range from 0-15 ppt (Table 4).

Table 3. Catch per Unit Effort

26

Table 4. Temperature and salinity reading for 5 months of sampling from October 2014 to February 2015

No. of Samplin

gs

Date

Temperature (°C)

Salinity (ppt)

1 Oct. 9 22-25 0-15

2 Oct. 29 - -

3 Nov. 7 23-25 0-10

4 Nov. 22 23-24 0-10

5 Dec. 6 - -

6 Dec. 22 22-24 0-10

7 Jan. 5 22-24 0-10

8 Jan. 20 23-24 0-10

9 Feb. 4 26-27 0-10

10 Feb. 19 26-28 0-10

CONCLUSION AND RECOMMENDATION

After five (5) months of sampling from October 2014 to February 2015, in

Pangi River, Maitum Sarangani Province, the large catches of freshwater eels

were during the new moon, with the largest catch on November 22, 2014 with

3,560 species. During full moon phase, very minimal catch was observed with

the largest catch of 10 pcs Anguillid eels on November 7, 2014. From these

catches two types of species were identified; A. marmorata and A. bicolor

pacifica.

A. marmorata was the most abundant anguillid eels in all the samplings

with a total of 4,123 individuals and had an abundance index of 96.73%,

frequency index of 100% and dominance index of 196.73%. On the other hand,

there were only 139 pcs of A. bicolor pacifica collected with abundance index of

3.26%, frequency index of 42.86% and dominance index of 46.12%.

Catch per unit effort (CPUE) was computed every sampling based on the

corresponding catch after four (4) hours of setting the net traps. The highest

CPUE of 133.5 gm/hour was computed in the 4th sampling on Nov. 22, 2014

during the new moon, while the lowest CPUE of 0.075 gm/hour was in the 9th

sampling during full moon on February 4, 2015.

During the sampling days, temperature was read, which ranged from 22

°C to 28 °C. Temperature was low ranging from 22 °C to 25 °C during samplings

28

in October 2014 until January 2015, and then increased in the month of February

2015 with temperature readings from 26 °C to 28 °C. Salinity levels were read

with a range from 0-15 ppt.

Further study is recommended to extend the stretch of sampling site

beyond Station 3 to monitor migration pattern of freshwater eels upstream the

river of Pangi, Maitum, Sarangani Province. Also to complete the one year data

on the abundance and distribution of freshwater eels, a similar study shall be

conducted for a period of one year.

29

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APPENDICES

34

Appendix Figure 1. Recording the collected eels

Appendix Figure 2. Sorting of the animals caught

35

Appendix Figure 3. The collected species of anguillid eels on Nov. 22,2014

Appendix Figure 4. Monitoring of water temperature and salinity during sampling

36

Appendix Figure 5. Weighing of Samples

Appendix Figure 6. GPS and plastic measuring tape used in the study

37

Appendix Figure 7. Determining the samples using morphological characteristics

Appendix Figure 8. Preserved Samples and Ethanol used as preservative

38

Appendix Figure 9. Adult Anguilla marmorata trapped in Station 3

Appendix figure 10. Tail bud of A. bicolor pacifica and A. marmorata

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Appendix figure 11. Other species trapped in the net traps during samplings (Freshwater crabs “Katang”, conger eel, and sea-snakes)