Do environmental factors affect recruit per spawner anomalies in the

1. Do environmental factors affect recruit per spawner anomalies in the Gulf of Maine - Southern New England region ? Jon Brodziak and Loretta O’Brien NOAA Fisheries Northeast Fisheries Science Center Population Dynamics Branch Woods Hole, Massachusetts, USA

2. Areas: • Gulf of Maine • Georges Bank • Southern New England • 12 groundfish stocks • Time series: • 1931 –2001 (range) • 16-71 years

7. Recruitment Survival • RS = recruitment / SSB • Standardized RS anomalies

12. Randomization Tests Ho: There is no year effect in RS anomalies

13. RS anomalies Each area and year:

14. Year effects (P = 0.1) Randomization Tests Manly 1997

15. Nantucket

16. Nantucket

17. Generalized Additive Model Analysis Response variable • Standardized RS anomaly Predictor variables • Surface and bottom temperature • Northwest Atlantic Oscillation Index : NAO • Modeled wind stress • Shelf water anomaly Linear predictor in GLM, is replaced by an additive predictor

18. Surface and Bottom Temperature Anomaly Data • 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

19. Principal Component Analysis: Temperature Anomaly Variability explained by 1st and 2nd PC: GM: 78% GB: 92% SNE:88%

20. NAO Index • NAO Winter Index: Average of ( Decyr-1 + Janyr + Feb yr +Maryr) • NAOyr • NAOyr-1 • NAOyr-2 http://www.cru.uca.ac.uk

21. Wind data Moored Buoys

22. Buoy Locations: Modeled Wind • Wind speed and direction: - recorded every 6 hours - estimated monthly mean • Species specific wind stress and direction: 1-6 month average • Derived an index of shoreward transport [cos (direction +90 deg ) * wind stress] + shoreward transport - offshore transport

23. Shelf Water Anomaly • Shelf water : • primary water mass in MAB • Formed by 2 sources: • Scotian Shelf Water • (cold, low salinity) • Slope Water • (warm, high salinity) Mountain 2004

24. 10 : significant NAO effects • 4 : significant temperature effect • 2 : significant wind effect • 10 : significant NAO lag 2 effect • 9 : significant NAO lag 1 effect • 2 : significant NAO effect

25. Gulf of Maine Redfish RS ~ PCA2 + NAO1 + NAO2 + Wind

26. Georges Bank Haddock RS ~ PCA1 + NAO + NAO2

27. Summary • Meta-analysis useful to discern patterns among stocks • Able to detect significant year effects in the RS time series • -1987 ‘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.

28. Acknowledgements • Jim Manning, NEFSC • Jerry Norton, SWFSC • Greg Lough, NEFSC • Laurel Col, NEFSC • Betty Holmes, NEFSC