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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. Outline. stock-recruit-environment relations mechanisms for recruit-env’t relation.
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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
Outline • stock-recruit-environment relations • mechanisms for recruit-env’t relation
Northern ShrimpPandalus borealis • Boreal distribution • Gulf of Maine=southern limit • Locally important fishery from Shumway et al. 1985 Life history Fishery
Impetus • Conventional wisdom: temperature = primary regulating factor • will “…not respond well to attempts to control exploitation” (Apollonio et al. 1986)
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
Analysis • Box-Jenkins TSA to ID factors affecting recruitment • S-R with environmental inputs
SSB 2 + Spring Surface TA - Spring Bottom TA 4 - NAO 1 - Results – TSASignificant crosscorrelations with recruitment Lag Sign 1 Planktonic larvae Male maturation, gender transition without 2002
Conclusion • Shrimp recruitment dependent on SSB and spring temperatures (surface and bottom)
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?
Match-Mismatch Hypothesis • Coastal Gulf of Maine: Bloom timing determined by solar insolation (Townsend and coauthors) • Shrimp development: temperature-dependent
Match-Mismatch Hypothesis • Bloom timing • Hatch timing • Survival rates
Bloom Timing • Townsend and Cammen (1988): 1971-1980 • CZCS and SeaWifs ’78-’86, ’98-’03
Hatch Dates • Maine DMR fishery sampling, 1980-1983 and 1989-1993 • Probit analysis: 50% hatch, duration of hatch
Shrimp Development • temperature-dependent
Larval Shrimp Diet • Zooplankton bloom ~ one month later (Townsend 1984) Stage I larvae Stickney and Perkins (1980)
Application • Management: Adjust fishing effort to allow higher egg deposition in warmer years
Summary Stephen H. Clark 1) SSB and spring temperatures affect GoM shrimp rcrt 2) Spring SST effect may be mediated through match-mismatch
Ongoing Work • Bloom timing • Solar insolation, 1982-1999 • CZCS / SeaWiFS, ‘83-’91, ‘97-’03 • Hatch timing