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Environmental Effects on Recruitment of Northern Shrimp in the Gulf of Maine Anne Richards Michael Fogarty David Mountain NOAA National Marine Fisheries Service Woods Hole, MA
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stock-recruit-environment relations mechanisms for recruit-env’t relation Outline
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Northern Shrimp Pandalus borealis Boreal distribution Gulf of Maine=southern limit Locally important fishery from Shumway et al. 1985 Life history Fishery
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Impetus Conventional wisdom: temperature = primary regulating factor will “…not respond well to attempts to control exploitation” (Apollonio et al. 1986)
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Stock-Recruitment Series 1968-2002
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Environmental Variables Temperature anomalies (W Gulf of Maine) –fall bottom: developmental rates, egg parasitism –spring bottom: developmental rates, hatch timing –spring surface: larval development NAO winter index
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Analysis Box-Jenkins TSA to ID factors affecting recruitment S-R with environmental inputs
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Results – TSA Significant crosscorrelations with recruitment 1 -4 Spring Bottom TA -1NAO - Spring Surface TA +2SSB LagSign without 2002 Planktonic larvae Male maturation, gender transition
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Stock-Recruitment Models Time periodVariables testedModel r 2 1968-2001SSB Spring surface TA Spring bottom TA r 2 =0.46 1968-2002SSB Spring surface TA Spring bottom TA r 2 =0.29
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Stock-Recruit-Temperature
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Conclusion Shrimp recruitment dependent on SSB and spring temperatures (surface and bottom)
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Mechanisms: Spring SST Spring surface temperature effect (larvae): –Appears intuitively correct –But counters laboratory studies: better growth and survival at warmer temperatures. –Indirect effect, e.g. match-mismatch?
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Match-Mismatch Hypothesis Coastal Gulf of Maine: Bloom timing determined by solar insolation (Townsend and coauthors) Shrimp development: temperature- dependent
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Match-Mismatch Hypothesis –Bloom timing –Hatch timing –Survival rates
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Bloom Timing Townsend and Cammen (1988): 1971-1980 CZCS and SeaWifs ’78-’86, ’98-’03
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Hatch Dates Maine DMR fishery sampling, 1980-1983 and 1989-1993 Probit analysis: 50% hatch, duration of hatch
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Hatch Timing
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Shrimp Development temperature-dependent
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Bloom Onset and Hatch Timing
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Survival
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Larval Shrimp Diet Zooplankton bloom ~ one month later (Townsend 1984) Stickney and Perkins (1980) Stage I larvae
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Implications
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Application Management: Adjust fishing effort to allow higher egg deposition in warmer years
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Stephen H. Clark Summary 1) SSB and spring temperatures affect GoM shrimp rcrt 2) Spring SST effect may be mediated through match-mismatch
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Ongoing Work Bloom timing –Solar insolation, 1982- 1999 –CZCS / SeaWiFS, ‘83-’91, ‘97-’03 Hatch timing
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