Dynamic programming part II

1. Dynamic programming part II Life history evolution in cod From individual states to populations

2. Evolutionemerges Trade-offs emerge A population is a collection of individuals and their actions Patterns emerge Bioenergetics Physical forcing Individual state

3. Northeast Arctic cod Marshall CT, Yaragina NA, Ådlandsvik B, and Dolgov AV. 2000. Reconstructing the stock-recruit relationship for Northeast Arctic cod using a bioenergetic index of reproductive potential. Can. J. Fish. Aquat. Sci., 57: 2433-2442.

4. Recruitment Something Why is state dependence important? An example: Recruitment in fish. ?

5. Recruitment What is ’something’ that we can measure? But, what about juvenile and immature stages? But, what about mature fish that do not spawn? Mature biomass? Biomass? Spawning stock biomass?

6. Recruitment in Icelandic cod Marteinsdottir G and Thorarinsson K. 1998. Improving the stock-recruitment relationship in Icelandic cod (Gadus morhua) by including age diversity of spawners. Can. J. Fish. Aquat. Sci., 55: 1372-1377.

7. Recruitment What is ’something’ that we can measure? Spawning stock biomass? SSB and age?

8. Recruitment to age 3 Condition and recruitment Marshall CT, Yaragina NA, Ådlandsvik B, and Dolgov AV. 2000. Reconstructing the stock-recruit relationship for Northeast Arctic cod using a bioenergetic index of reproductive potential. Can. J. Fish. Aquat. Sci., 57: 2433-2442.

9. Recruitment What is ’something’ that we can measure? SSB and age? SSB and condition?

10. Population structure • Describing a population by more than abundance or biomass: • Length. • Age and length. • Age and length and condition. Patterns in a structured population. A state-dependent dynamic programming model.

11. States External factors Age Body length Stored energy Mortality Food intake Migration costs Food intake Growth Stored energy Offspring A model for energy allocation Bioenergetic description of energy allocation. State-dependent life history optimized using reproductive value. Model presented in: Jørgensen C and Fiksen Ø. In press. State-dependent energy allocation in cod (Gadus morhua). Can J Fish Aquat Sci.

12. Energy utilization in the model Food ingested monthly (variable) – Routine metabolism = Energy for allocation [Spawning season]: Total stored energy – Energy required for migration (both ways) = Energy available for egg production Store Growth

13. State dynamics Stochasticity Growth: EG dG · (1-a) Energy infood E a Energy stores: dS · a ES At spawning: { ( ) } = × a a + V ( , S ) max P V a+1,L , S Fec a,L + + + 1 1 1 t S t t t a

14. Allocation Model presented in: Jørgensen C and Fiksen Ø. In press. State-dependent energy allocation in cod (Gadus morhua). Can J Fish Aquat Sci.

16. Predicted growth in the model

17. Life history evolution: Effects of fisheries

18. Northeast Arctic cod Feeder fishery Feeder fishery Feeder fishery Since ~1920 Spawner fishery Spawner fishery Spawner fishery More than 1000 years

19. Historic fishing Mean ageat maturation (year) Present trawling Mortality in spawnerfishery (year-1) Mortality in feederfishery (year-1)

20. Skipped spawning

21. Allocation Model presented in: Jørgensen C and Fiksen Ø. In press. State-dependent energy allocation in cod (Gadus morhua). Can J Fish Aquat Sci.

22. Effects of mortality • In general: • Increasing mortality decreases the value of future reproductions. • Current reproduction becomes more important. • Skipped spawning becomes less frequent.

24. Skipped spawning: Ecological relationships

25. The effect of condition

26. Richard Nash, Institute of Marine Research, unpublished data. Interaction: condition and length Spawning Not spawning

27. Relationship with food availability

28. Skipped spawning (% of repeat spawners) Natural mortality (year-1) Relative food intake

29. Skipped spawning: Relationships with age

30. Skipped spawning and age Harvest: Skipped spawning more common Evolution: Skipped spawning less common Historic growth Present growth Continued fishing

31. Histology in Barents Sea cod Barents Sea Bear Island bank Oganesyan, S. A. (1993). Periodicity of the Barents Sea cod reproduction. ICES CM 1993/G:64.

32. Young mature cod skip more Present growth Historic growth Continued fishing

33. Spawning area 1st-time spawners Evidence of skipping 2nd-time spawners ‘5th-time spawners’ 2nd-time spawners strongly underrepresented Slide and data courtesy of Georg Engelhard and Mikko Heino.

34. Recruitment Something How to predict recrutiment?

35. Individual state and fecundity Fecundity (million eggs) Fecundity (million eggs) Fecundity (million eggs) Fecundity (million eggs)

36. Including Energy Stores Removing Skipped Spawners Population measures and fecundity

37. Total egg production Fecundity (million eggs) Liver energy and fecundity Individual Population

38. Evolutionemerges Trade-offs emerge A population is a collection of individuals and their actions Patterns emerge Bioenergetics Physical forcing Individual state

39. Acknowledgements • Collaborators and co-authors: Øyvind Fiksen (supervisor) Bruno Ernande Ulf Dieckmann Mikko Heino Richard Nash • Thanks to the Research Council of Norway for financial support.