1. Comparative selectivity on length at maturity among Alaskan sockeye salmon fisheries Neala Kendall Tom Quinn School of Aquatic and Fishery Sciences University of Washington Seattle, WA, USA M. Bond

2. Need for evaluating harvest selection  Life history traits are changing over time (Darimont et al. 2009 PNAS)

3. Need for quantifying harvest selection  Life history traits are changing over time (Darimont et al. 2009 PNAS)  Importance of quantifying harvest selection (Carlson et al. 2007 Ecology Letters, Edeline et al. 2007 PNAS)

4. Need for quantifying harvest selection  Life history traits are changing over time (Darimont et al. 2009 PNAS)  Importance of quantifying harvest selection (Carlson et al. 2007 Ecology Letters, Edeline et al. 2007 PNAS)  Evaluating implications of selection (Olsen et al. 2004 Nature, Heino and God Ø 2002 Bulletin of Marine Science)

5. Difficult to quantify fishery selection Hutchings, Nature 2005 Fish caught Length Fishery selectivity curve ?

6. Alaska salmon: good model to study fishery selection  Semelparous  Anadromous  Length and age at maturity easy to measure  Know population size and structure  Long-term gillnet fisheries  Large, long term data set J. Carter

7. Research questions  Does fishery selection vary by fish length and sex? J. Carter

8. Research questions  Does fishery selection vary by fish length and sex?  Are fish length at age changes over time correlated with fishery selection? J. Carter

9. Alaska sockeye salmon fisheries Bristol Bay Upper Cook Inlet Alaska

10. Methods  Yearly historical fishery reconstruction  Characterize annual length distributions in catch, escapement (not caught), and total run  Estimate: 1) Length-specific vulnerability 2) Selection differentials

11. Length frequency histogram example Females Males

12. Vulnerability profiles by length Females Males 1990 19941999 20022003 400 650 400 650 400 650 0 1 0 1

13. Selection on length: SSDs SSD Larger fish are escaping to spawn than are getting caught + - Smaller fish are escaping to spawn than are getting caught Standardized selection differential = length escapement – length total run std. deviation of length total run

14. J. Carter Female SSDs more consistently negative than male SSDs Female average Male average

15. Fishery selection on Bristol Bay sockeye salmon and length at age changes over time

16. Differential fishery selection on ocean age 2 fish Proportion frequency Standardized selection differential P < 0.001 P = 0.143 P < 0.001 P = 0.002 P < 0.001 P = 0.051 P = 0.010 P = 0.756 Nushagak Naknek-Kvichak Egegik Ugashik Togiak Nushagak Naknek-Kvichak

17. Average length of ocean age 2 fish has decreased over time Average length (mm) slope=-0.60 slope=-0.64 slope=-0.26 slope=-0.31 slope=-0.16 slope=-0.05 slope=-0.19 slope=-0.21 slope=-0.16 slope=-0.21 450 550 450 550 Average length (mm) 450 550 450 550 Egegik Ugashik Togiak Nushagak Naknek-Kvichak slope: P = 0.003 slope: P = 0.033 slope: P = 0.005 slope: P = 0.218 slope: P = 0.869

18. SSDs somewhat correlated with decreasing length at age over time

19. Conclusions  Are larger than average fish more vulnerable to being caught ? YES Fish caught ConclusionsConclusions

20. Males  Does the fishery harvest different lengths of males than females? YES Length Females Conclusions

21.  Are fish length at age changes over time correlated with fishery selection? YES Fishing districts that harvest larger fish show a greater decline in fish length at age over time Conclusions

22.  Mary Beth Loewen and Matt Foster, ADFG  Mark Willette and Terri Tobias, ADFG  Tim Baker, ADFG  Jeff Hard, NOAA Fisheries  Alaska Salmon Program, UW  Funding: School of Aquatic and Fishery Sciences Alaska Sustainable Salmon Fund National Science Foundation Gordon and Betty Moore Foundation Acknowledgements

24. J. Bennis J. Carter

25. Bristol Bay—100% gillnets

26. Chignik—100% purse seines

27. Alitak—mixed purse seines/gillnets

28. Vulnerability differs by length & sex example Females J. Carter Males

29. Females Vulnerability curves differ among years J. Bennis Length (mm) 19801991 2002 420 620 420 620 420 620 J. Carter

30. Vulnerability profiles Chignik female

31. Vulnerability profiles Chignik male

32. Vulnerability profiles Upper Cook Inlet female

33. Vulnerability profiles Upper Cook Inlet male

34.  Using estimated selectivities, model ideal length and age at maturity under different harvest scenarios (J Ø rgensen et al. 2009 Evol. Apps.)  Calculate maturation reaction norms for spawning populations J. BennisJ. Carter Future work, extensions J. Bennis