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

stock-recruit-environment relations mechanisms for recruit-env’t relation Outline

Northern Shrimp Pandalus borealis Boreal distribution Gulf of Maine=southern limit Locally important fishery from Shumway et al Life history Fishery

Impetus Conventional wisdom: temperature = primary regulating factor will “…not respond well to attempts to control exploitation” (Apollonio et al. 1986)

Stock-Recruitment Series

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

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

Stock-Recruitment Models Time periodVariables testedModel r SSB Spring surface TA Spring bottom TA r 2 = SSB Spring surface TA Spring bottom TA r 2 =0.29

Stock-Recruit-Temperature

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): CZCS and SeaWifs ’78-’86, ’98-’03

Hatch Dates Maine DMR fishery sampling, and Probit analysis: 50% hatch, duration of hatch

Hatch Timing

Shrimp Development temperature-dependent

Bloom Onset and Hatch Timing

Survival

Larval Shrimp Diet Zooplankton bloom ~ one month later (Townsend 1984) Stickney and Perkins (1980) Stage I larvae

Implications

Application Management: Adjust fishing effort to allow higher egg deposition in warmer years

Stephen H. Clark Summary 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, –CZCS / SeaWiFS, ‘83-’91, ‘97-’03 Hatch timing