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ICES annual symposium, Bergen, 14 May 2004

Non-additive effects of environmental variables on the recruitment of walleye pollock ( Theragra chalcogramma ) in the Gulf of Alaska. Does the intensity of density-dependent control change over contrasting environmental phases?.

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ICES annual symposium, Bergen, 14 May 2004

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  1. Non-additive effects of environmental variables on the recruitment of walleye pollock (Theragra chalcogramma) in the Gulf of Alaska Does the intensity of density-dependent control change over contrasting environmental phases? L. Ciannelli - NOAA, SeattleK. Bailey - NOAA, Seattle N.C. Stenseth – CEES, University of Oslo, NorwayK.S. Chan - University of IowaA. Belgrano - University of New Mexico ICES annual symposium, Bergen, 14 May 2004

  2. Pollock early life cycle 3 ACC

  3. GAM: additive non-additive continuous CGAM: if E<= E* non-additive threshold TGAM: otherwise Analysis • Hypothesis:non-additive effect of DI and demographic variables on pre-recruitment survival: variable levels of DD Model selection criteria

  4. Data: demographic variables F(SB) Survey Catch-at-age models Survey

  5. Data: environmental variables Spring (TS) and Fall (TF) SST (Wind speed)3 = W TF TS Groundfish predation index (PG) W and TS = egg to age-0 PG and TF = age-0 to age-1 age-1 to age-2

  6. Results: model selection Model Structure Variables CV

  7. GAM CGAM TGAM Egg to Age0 TS TS TS Age-0to Age-1 TF TF TF Age-1 to Age-2 PG TF Results: effects

  8. Results: TGAM partitions

  9. DATA GAM CGAM TGAM Results: model simulations GAM-R2 = 0.43 CGAM-R2 = 0.58 TGAM-R2 = 0.65 GAM-R2 = 0.36 CGAM-R2 = 0.44 TGAM-R2 = 0.51 GAM-R2 = 0.59 CGAM-R2 = 0.64 TGAM-R2 = 0.69

  10. DATA GAM CGAM TGAM Results: model simulations GAM-R2 = 0.43 CGAM-R2 = 0.58 TGAM-R2 = 0.65 GAM-R2 = 0.36 CGAM-R2 = 0.44 TGAM-R2 = 0.51 GAM-R2 = 0.59 CGAM-R2 = 0.64 TGAM-R2 = 0.69

  11. DATA GAM CGAM TGAM Results: model simulations GAM-R2 = 0.43 CGAM-R2 = 0.58 TGAM-R2 = 0.65 GAM-R2 = 0.36 CGAM-R2 = 0.44 TGAM-R2 = 0.51 GAM-R2 = 0.59 CGAM-R2 = 0.64 TGAM-R2 = 0.69

  12. Factors affecting recruitment: cross-scales (wind, temperature, community change) change across-stages (egg-age0; age0-1, age1-2) are non additive, i.e., interact with each other (changes of DD) Summary • New Question: • How do these patterns affect our ability to forecast/manage pollock stocks in changing environment?

  13. Climate in North Pacific

  14. Temperature in the GOA

  15. Community changes in the GOA

  16. Immediately after the regime shift, larval mortality and recruitment were correlated Afterwards, the relationship dissipated There has been no trend in larval mortality There has been a trend for increasing juvenile mortality Control has shifted from environmental effects on larvae to predation of juveniles. Bailey (2000) MEPS 198:215

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