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STFA Spiny Lobster Project Third Progress Report 8/12/2013
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Virgin Islands Spiny Lobster Landings
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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?
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Island Differences in Methods 2010 CCR Data Island DivingTraps St. Thomas/St. John 1.7% 98.3% St. Croix92.4%7.6% Average sizes are significantly different between Islands (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)
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Distribution of 2006 Lobster Landings
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# Lobster Trips by Island (1974-2006)
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% of Lobster by CL (Complete Trips) Minimum Legal CL
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Island Differences in Sizes CFMC Project Complete Trips Island Average CL St. Thomas/St. John 101.9 mm St. Croix91.9 mm Difference significant at 0.001 level
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St. Croix Size of Lobster Traps vs Diving Anova: Single Factor SUMMARY Groups CountSumAverageVariance Traps 990105,236 106.30 220 Diving 2,451262,190 106.97 250 ANOVA Source of Variation SSdfMSF P- valueF crit Between Groups 3191 1.320.2513.844 Within Groups 833,2763,439242 Total 833,5963,440
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Monthly Landings: St. Thomas
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Monthly Landings: St. Croix
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Short/Berried Seasonality
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St. Thomas Tags and Recaptures Month Cumulative # Tagged Adjusted for Mortality Project Recaptures Non-Project Recaptures# Kept September-12492 612 October-12126712551511 November-12158615451624 December-121884181429212 January-13215120422629 February-13241922642038 March-13267524652414 April-13326930003247 May-133593327228327 June-133843344626310 July-133957347816119 August-13 3957347823833 (12%)93
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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.
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STFA Lobster Landings (% of Total Lobster Landings)
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Average Monthly Percentage Projected Monthly Landings # Lobsters Project Lbs Caught % of Projected Landings September7.3%6,1653,447101513.0% October8.2%6,9342,997212531.3% November8.6%7,2493,152229232.1% December10.7%8,9853,005318446.8% January10.6%8,9083,380142618.7% February9.2%7,7222,989201429.8% March9.4%7,9383,253248033.7% April8.7%7,3362,921360654.6% May7.3%6,1562,732229237.1% June6.3%5,2712,286173133.5% July6.9%5,8133,416114614.8%
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Mortality Adjusted Population Estimate
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St. Thomas Average CL
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St. Croix Average CL
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Mortality Calculation
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Total Mortality (Z) Calculated from TIP Data
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Yield Per Recruit
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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?
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Comparison Between Annual Fish Trap Hauls (CCR Reports and Fishermen Interviews)
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Comparison Between Annual Lobster Trap Hauls (CCR Reports and Fishermen Interviews)
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FISHER CODEYEAR FISH_POTS_IN_WATE R LOBSTER_POTS_ IN_WATER COMBINED_TRAPS_IN_ WATER FISH_TRAPS_ HAULED LOBSTER_TRAP S_HAULED GEAR_TYPE_HAUL ED COMBINED_TR APS_HAULEDTRIPS B/C2011(blank) 82(blank) Traps01 B/C2011(blank) 110(blank) Traps01 B/C2012(blank) 82(blank) Traps01 B/C2012(blank) 85(blank) Traps02 B/C2012(blank) 90(blank) Traps03 B/C2012(blank) 110(blank) Traps01 J2011(blank) 110(blank) Traps01 J2011(blank) Traps01 J2012(blank) 110(blank) Traps01 J2012(blank) 120(blank) Traps02 J2012(blank) Traps01 S2012(blank) 194(blank) Traps01 U2011(blank) 5 Traps01 U2012(blank) 5 Traps03 U2012(blank) Traps02 U2013(blank) 5 Traps02 U2013(blank) Traps01 V2011(blank) 201(blank)Traps, Fish18 V2011(blank) 1 Traps, Fish11 V2012(blank) 201(blank)Traps, Fish123 W2012(blank) 700(blank) Traps01 Y2012(blank) 10(blank) Traps01 Z2012(blank) 68(blank) Traps08 Z2012(blank) 76(blank) Traps01 AB2012(blank) 530(blank) Traps01 AG2011(blank) 4 1Traps, Lobster11 AG2011(blank) 30(blank)1Traps, Lobster11 AG2012(blank) 5 1Traps, Lobster12 AJ2012(blank) 182(blank) Traps01 AT2011(blank) 610(blank) Traps01 AY2012(blank) 97(blank) Traps01 AY2012(blank) 102(blank) Traps01
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Traps/Day Hauled in St. Thomas (TIP, Historic and Adjusted CCR Data)
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Total STT/STJ Lobster Landings (lbs x 1000)
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STT Stock Health Indicators
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Total STX Lobster Landings
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STX Stock Health Indicators
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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.
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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.
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