Do environmental factors affect recruit per spawner anomalies in the Gulf of Maine - Southern New England region ? Jon Brodziak and Loretta OBrien NOAA Fisheries Northeast Fisheries Science Center Population Dynamics Branch Woods Hole, Massachusetts, USA Areas: Gulf of Maine Georges Bank Southern New England 12 groundfish stocks Time series: 1931 2001 (range) years RS = recruitment / SSB RS = recruitment / SSB Standardized RS anomalies Standardized RS anomalies Recruitment Survival Randomization Tests H o : There is no year effect in RS anomalies RS anomalies Each area and year: Year effects (P = 0.1) Manly 1997 Randomization Tests Nantucket Generalized Additive Model Analysis Response variable Standardized RS anomaly Standardized RS anomaly Predictor variables Surface and bottom temperature Surface and bottom temperature Northwest Atlantic Oscillation Index : NAO Northwest Atlantic Oscillation Index : NAO Modeled wind stress Modeled wind stress Shelf water anomaly Shelf water anomaly is replaced by an additive predictor Linear predictor in GLM, Each area: Gulf of Maine, Georges Bank, So. New England 2 Seasons: Spring and Autumn 4 temperature observations / area spring surface and bottom autumn surface and bottom Surface and Bottom Temperature Anomaly Data Principal Component Analysis: Temperature Anomaly Variability explained by 1 st and 2 nd PC: GM: 78% GB: 92% SNE:88% NAO Winter Index: Average of ( Dec yr-1 + Jan yr + Feb yr +Mar yr ) NAO yr NAO yr-1 NAO yr-2 NAO Index Wind data Moored Buoys Buoy Locations: Modeled Wind Wind speed and direction: Wind speed and direction: - recorded every 6 hours - recorded every 6 hours - estimated monthly mean - estimated monthly mean Species specific wind stress and direction: Species specific wind stress and direction: 1-6 month average 1-6 month average Derived an index of shoreward transport Derived an index of shoreward transport [cos (direction +90 deg ) * wind stress] [cos (direction +90 deg ) * wind stress] + shoreward transport + shoreward transport - offshore transport - offshore transport Shelf Water Anomaly Mountain 2004 Shelf water : primary water mass in MAB Formed by 2 sources: Scotian Shelf Water (cold, low salinity) Slope Water (warm, high salinity) 10 : significant NAO lag 2 effect 10 : significant NAO lag 2 effect 9 : significant NAO lag 1 effect 9 : significant NAO lag 1 effect 2 : significant NAO effect 2 : significant NAO effect 10 : significant NAO effects 10 : significant NAO effects 4 : significant temperature effect 4 : significant temperature effect 2 : significant wind effect 2 : significant wind effect Gulf of Maine Redfish RS ~ PCA 2 + NAO 1 + NAO 2 + Wind Georges Bank Haddock RS ~ PCA 1 + NAO + NAO 2 Summary Meta-analysis useful to discern patterns among stocks Able to detect s ignificant year effects in the RS time series wind event increased advection (Polachek et al 1992) - Investigate what factors influenced other years with extreme RS values,i.e.1998 Environmental factors have non-linear effect on RS anomalies Longer time series were more informative RS time series >20 years had sign. temperature and wind effects RS time series < 21 years: no detectable differences from a random time series NAO global variable: proxy for local climate event Further work /ongoing work determine mechanisms and inter-relationships: circulation, local wind, seasonal stratification, spawning variability, predator/ prey composition, temperature/growth, etc. Acknowledgements Jim Manning, NEFSC Jim Manning, NEFSC Jerry Norton, SWFSC Jerry Norton, SWFSC Greg Lough, NEFSC Greg Lough, NEFSC Laurel Col, NEFSC Laurel Col, NEFSC Betty Holmes, NEFSC Betty Holmes, NEFSC