stfa spiny lobster project third progress report 8/12/2013
DESCRIPTION
On both islands periods of high lobster landings (St. Thomas/St. John from , 136,000 lbs and St. Croix , 156,000 lbs) were followed by decreased landings which have not returned to prior levels. Did these levels represent overfishing? If so, what levels can be sustained?TRANSCRIPT
STFASpiny Lobster Project
Third Progress Report 8/12/2013
Virgin Islands Spiny Lobster Landings
19741976
19781980
19821984
19861988
19901992
19941996
19982000
20022004
20062008
20100
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
St. Croix ACL= 107,307 lbs
St. Thomas/St. John ACL= 104,199 lbs
Year
Land
ings
(lbs
)
• On both islands periods of high lobster landings (St. Thomas/St. John from 2003-2006, 136,000 lbs and St. Croix 2006-2009, 156,000 lbs) were followed by decreased landings which have not returned to prior levels.• Did these levels represent overfishing?• If so, what levels can be sustained?
Island Differences in Methods2010 CCR Data
Island Diving Traps
St. Thomas/St. John 1.7% 98.3%
St. Croix 92.4% 7.6%
Average sizes are significantly different betweenIslands (F= 102.7, p<0.001)
Difference between size of Trap and SCUBA caught lobsters on St. Croix not significant (F=0.76, p=0.38)
Distribution of 2006 Lobster Landings
1.004.00
7.0010.00
13.0016.00
19.0022.00
25.0028.00
31.0034.00
37.0040.00
43.0046.00
49.0052.00
55.0058.00
61.0064.00
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
St. CroixSt. Thomas
# Fishermen
% o
f Tot
al La
ndin
gs
# Lobster Trips by Island (1974-2006)
9741976
19781980
19821984
19861988
19901992
19941996
19982000
20022004
20060
500
1000
1500
2000
2500
3000
3500
4000
St. Croix
St. Thomas/St. John
% of Lobster by CL (Complete Trips)
0%
5%
10%
15%
20%
25%
30%
35%
ST. CroixSt. Thomas
Minimum Legal CL
Island Differences in SizesCFMC Project Complete Trips
Island Average CL
St. Thomas/St. John 101.9 mm
St. Croix 91.9 mm
Difference significant at 0.001 level
St. Croix Size of LobsterTraps vs Diving
Anova: Single Factor
SUMMARY
Groups Count Sum Average Variance
Traps 990 105,236 106.30 220
Diving 2,451 262,190 106.97 250
ANOVASource of Variation SS df MS F
P-value F crit
Between Groups 319 1 319 1.32 0.251 3.844
Within Groups 833,276 3,439 242
Total 833,596 3,440
Monthly Landings: St. Thomas
January
February
March AprilMay
JuneJuly
August
September
October
N ovember
December
0%
2%
4%
6%
8%
10%
12%
14%
16% 1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2006
2005
Average
Monthly Landings: St. Croix
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
20%1991199219931994199519961997199819992000200120022003200420052006Average
Short/Berried Seasonality
September-1
2
October-1
2
November-1
2
December-1
2
January
-13
February
-13
March-13
April-13
May-13
June-13
July-13
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Shorts CPUEBerried CPUE
Shor
t Lob
ster
s/Tr
ap H
aul
Berr
ied
Lobs
ters
/Tra
p Ha
ul
St. Thomas Tags and RecapturesMonth
Cumulative # Tagged
Adjusted for
MortalityProject
RecapturesNon-Project Recaptures # Kept
September-12 492 492 6 1 2October-12 1267 1255 15 1 1
November-12 1586 1545 16 2 4December-12 1884 1814 29 2 12
January-13 2151 2042 26 2 9February-13 2419 2264 20 3 8
March-13 2675 2465 24 1 4April-13 3269 3000 32 4 7May-13 3593 3272 28 3 27June-13 3843 3446 26 3 10July-13 3957 3478 16 11 9
August-13 3957 3478 238 33 (12%) 93
Summary of Coral World Tag Retention Study
• 22 lobsters were installed at Coral World on 8 May 2013.
• To date there have been 4 molts with no tag loss.• On about 15 July some UVI students who were doing a
lionfish study removed the grate separating the lobsters from the pump intake, resulting in total mortality.
• We are waiting to restock until catches of small lobsters increase.
• In the mean-time we have tagged an additional 10 (very) small Coral World Lobsters.
0 20 40 60 80100
120140
160180
200220
240260
280300
320340
0
10
20
30
40
50
60
# Recaptures/ Days at Large
# Days at Large
STFA Lobster Landings (% of Total Lobster Landings)
2,003.00 2,004.00 2,005.00 2,006.0080,000
90,000
100,000
110,000
120,000
130,000
140,000
150,000
75%
80%
85%
90%
95%
100%Total Lobster LandingsSTFA Lobster LandingsSTFA % of Total
Lobs
ter L
andi
ngs (
lbs)
Average Monthly
Percentage
Projected Monthly Landings
# LobstersProject Lbs
Caught% of Projected
Landings
September 7.3% 6,165 3,447 1015 13.0%
October 8.2% 6,934 2,997 2125 31.3%
November 8.6% 7,249 3,152 2292 32.1%
December 10.7% 8,985 3,005 3184 46.8%
January 10.6% 8,908 3,380 1426 18.7%
February 9.2% 7,722 2,989 2014 29.8%
March 9.4% 7,938 3,253 2480 33.7%
April 8.7% 7,336 2,921 3606 54.6%
May 7.3% 6,156 2,732 2292 37.1%
June 6.3% 5,271 2,286 1731 33.5%
July 6.9% 5,813 3,416 1146 14.8%
Mortality Adjusted Population Estimate
September
October
November
December
January
February
March
AprilMay
JuneJuly
August
200,000
250,000
300,000
350,000
400,000
450,000
St. Thomas Average CL
1970 1975 1980 1985 1990 1995 2000 2005 2010 201590
95
100
105
110
115
120
St. Croix Average CL
1980 1985 1990 1995 2000 2005 2010 201590.0
95.0
100.0
105.0
110.0
115.0
120.0CL
(mm
)
Mortality Calculation• Von Bertalanffy growth equation . • Solve for (t) for carapace length. • This provides the age for each size class in the size frequency
distribution so that total mortality (Z) Where: is the number of fish at time (t) and (t-1)andZ is the rate of total mortality.
can be calculated as the difference in numbers from the size class bin at full recruitment and the size class bin containing L
Total Mortality (Z) Calculated from TIP Data
19711981
19831985
19871989
19911993
19951997
19992001
20032005
20072009
2011
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
St. Thomas Moving average (St. Thomas)
St. Croix Moving average (St. Croix)
Tota
l Ann
ual M
orta
lity
(Z)
01224364860728496108120132144156168180
0 1224 3648 6072 8496 108120 132144 156168 180
Fishing mortality rate
Size
at fi
rst c
aptu
re (m
m ca
rapa
ce le
ngth
)
St. Thomas St. Croix
Yield Per Recruit
• On both islands periods of high lobster landings (St. Thomas/St. John from 2003-2006, 136,000 lbs and St. Croix 2006-2009, 156,000 lbs) were followed by decreased landings which have not returned to prior levels.• Did these levels represent overfishing?• If so, what levels can be sustained?
Comparison Between Annual Fish Trap Hauls(CCR Reports and Fishermen Interviews)
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 20070
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
450,000
500,000
CCR Reports Fishermen Interviews
Year
Tota
l Ann
ual T
rap
Hau
ls
Comparison Between Annual Lobster Trap Hauls(CCR Reports and Fishermen Interviews)
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 20070
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
CCR Trap Hauls/Day
Adjusted Trap Hauls /Day
FISHER CODE YEARFISH_POTS_IN_WATE
RLOBSTER_POTS_
IN_WATERCOMBINED_TRAPS_IN_
WATERFISH_TRAPS_
HAULEDLOBSTER_TRAP
S_HAULEDGEAR_TYPE_HAULED
COMBINED_TRAPS_HAULED TRIPS
B/C 2011 (blank) (blank) 82 (blank) (blank)Traps 0 1B/C 2011 (blank) (blank) 110 (blank) (blank)Traps 0 1B/C 2012 (blank) (blank) 82 (blank) (blank)Traps 0 1B/C 2012 (blank) (blank) 85 (blank) (blank)Traps 0 2B/C 2012 (blank) (blank) 90 (blank) (blank)Traps 0 3B/C 2012 (blank) (blank) 110 (blank) (blank)Traps 0 1J 2011 (blank) (blank) 110 (blank) (blank)Traps 0 1J 2011 (blank) (blank) (blank) (blank) (blank)Traps 0 1J 2012 (blank) (blank) 110 (blank) (blank)Traps 0 1J 2012 (blank) (blank) 120 (blank) (blank)Traps 0 2J 2012 (blank) (blank) (blank) (blank) (blank)Traps 0 1S 2012 (blank) (blank) 194 (blank) (blank)Traps 0 1U 2011 (blank) (blank) 5 (blank) (blank)Traps 0 1U 2012 (blank) (blank) 5 (blank) (blank)Traps 0 3U 2012 (blank) (blank) (blank) (blank) (blank)Traps 0 2U 2013 (blank) (blank) 5 (blank) (blank)Traps 0 2U 2013 (blank) (blank) (blank) (blank) (blank)Traps 0 1V 2011 (blank) (blank) 20 1 (blank)Traps, Fish 1 8V 2011 (blank) (blank) (blank) 1 (blank)Traps, Fish 1 1V 2012 (blank) (blank) 20 1 (blank)Traps, Fish 1 23W 2012 (blank) (blank) 700 (blank) (blank)Traps 0 1Y 2012 (blank) (blank) 10 (blank) (blank)Traps 0 1Z 2012 (blank) (blank) 68 (blank) (blank)Traps 0 8Z 2012 (blank) (blank) 76 (blank) (blank)Traps 0 1AB 2012 (blank) (blank) 530 (blank) (blank)Traps 0 1AG 2011 (blank) (blank) 4 (blank) 1Traps, Lobster 1 1AG 2011 (blank) (blank) 30 (blank) 1Traps, Lobster 1 1AG 2012 (blank) (blank) 5 (blank) 1Traps, Lobster 1 2AJ 2012 (blank) (blank) 182 (blank) (blank)Traps 0 1AT 2011 (blank) (blank) 610 (blank) (blank)Traps 0 1AY 2012 (blank) (blank) 97 (blank) (blank)Traps 0 1AY 2012 (blank) (blank) 102 (blank) (blank)Traps 0 1
Traps/Day Hauled in St. Thomas (TIP, Historic and Adjusted CCR Data)
1965 1970 1975 1980 1985 1990 1995 2000 2005 20100.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
f(x) = 1.79170982869248 x − 3525.0792390348R² = 0.939675637834702
TIPMARFINMRAGVIERSAdjusted CCR
Year
Trap
Hau
ls/D
ay
Total STT/STJ Lobster Landings(lbs x 1000)
19751977
19791981
19831985
19871989
19911993
19951997
19992001
20032005
20072009
20110
20000
40000
60000
80000
100000
120000
140000
160000
Divers Trap
Year
Land
ings
(lbs
x 1
000)
1970 1975 1980 1985 1990 1995 2000 2005 20100
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
STT Trap LandingsObserved LandingsPredicted Landings
Year
Land
ings
(kg)
1970 1975 1980 1985 1990 1995 2000 2005 20100
1000
2000
3000
4000
5000
6000
STT Diver LandingsObserved LandingsPredicted Landings
Year
Land
ings
(kg)
1970 1975 1980 1985 1990 1995 2000 2005 20100
0.20.40.60.8
11.21.41.61.8
2
STT Trap IndexObserved IndicesPredicted Indices
Year
Stan
dard
ized
CPUE
1970 1975 1980 1985 1990 1995 2000 2005 20100
0.5
1
1.5
2
2.5
STT Diver IndexObserved IndicesPredicted Indices
Year
Stan
dard
ized
CPUE
STT Stock Health Indicators
1975 1980 1985 1990 1995 2000 2005 20100
0.5
1
1.5
2
2.5
Trap CPUE Divers CPUE
Year
Rela
tive
CPU
E va
lue
1975 1980 1985 1990 1995 2000 2005 2010707580859095
100105110115120
Avg Length Minimum size Size at 50% Maturity
Year
Cara
pace
Len
gth
(mm
)
1970 1975 1980 1985 1990 1995 2000 2005 20100
2000
4000
6000
8000
10000
12000
14000
STX Trap LandingsObserved LandingsPredicted Landings
Year
Land
ings
(kg)
1970 1975 1980 1985 1990 1995 2000 2005 20100
10000
20000
30000
40000
50000
60000
70000
80000
STX Diver LandingsObserved LandingsPredicted Landings
Year
Land
ings
(kg)
1970 1975 1980 1985 1990 1995 2000 2005 20100
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2 STX Trap IndexObserved IndicesPredicted Indices
Year
Stan
dard
ized
CPUE
1970 1975 1980 1985 1990 1995 2000 2005 20100
0.5
1
1.5
2
2.5
3
STX Diver IndexObserved IndicesPredicted Indices
Year
Stan
dard
ized
CPUE
Total STX Lobster Landings
19751977
19791981
19831985
19871989
19911993
19951997
19992001
20032005
20072009
20110
20000
40000
60000
80000
100000
120000
140000
160000
180000
Divers Trap
Year
Land
ings
(lbs
x 1
000)
STX Stock Health Indicators
1975 1980 1985 1990 1995 2000 2005 20100
0.5
1
1.5
2Trap CPUEDivers CPUE
Year
Rela
tive
CPUE
val
ue
1975 1980 1985 1990 1995 2000 2005 2010707580859095
100105110115120
Avg Length Minimum size Size at 50% Maturity
Year
Cara
pace
Leng
th (m
m)
Summary of Status: St. Thomas• On St. Thomas, landings increased gradually from the mid-1980s to peaks of
just over 136,000 lbs in 2003 through 2006, followed by decreased landings following this period.
• During this time of historically high catches, the stock showed no consistent signs of decline in catch per unit effort or in the average size of catch.
• The average size of catch itself remained well above the minimum size limit and the size at first maturity.
• As such, catches of 130,000 lbs a year appear to be sustainable. Current OFL is 115,776 lbs.
• Ongoing catch reporting and port sampling allow us to watch for future signs of overfishing, and would allow for the opportunity to adjust catches downward if necessary.
Summary of Status: St. Croix• On St. Croix, landings grew dramatically starting in the mid-1990s to a
peak of over 155,000 lbs in 2008. Catches have exceeded 135,000 lbs most years since 2005.
• Indicators of health provide conflicting information. Whereas catch per unit effort has consistently increased since 2003, the average size of catch has mostly declined since 2007, with particularly dramatic drops in 2011 and 2012. The value in 2012 was close to the minimum size limit and size at first maturity, indicating lobster were being caught just as they grew to legal size and were capable of contributing new lobsters to the population.
• Given the data sources (port sampling versus self-reporting) and problems with assessing diving effort, the size information should probably receive greater consideration than catch per unit effort.
• While the size information is no guarantee that the stock is in poor condition, it does raise concerns about the current catch levels.
• Catches of 100,000 to 120,000 lbs were sustained in the early 2000s and may be a suitable quota, pending ongoing monitoring of this stock. Current OFL is 119,230 lbs.