Steelhead trout life history

1. Steelhead trout life history SDP/DSV models meet data W. Satterthwaite & M. Mangel - UCSC, D. Swank, S. Sogard, & M. Beakes - NOAA J. Merz - EBMUD, Cramer Fish Sciences R. Titus & E. Collins - CDFG

2. Thinking about steelhead life history • Why mature as resident? • Avoid ocean mortality • Potentially easier iteroparity • Why smolt and emigrate? • Much larger size > higher reproductive success • Why take action when young? • Less cumulative risk of mortality in stream • Why take action when older? • Larger size at spawning = higher reproduction • Larger size at emigration = higher survival

3. Tradeoff between future growth, further mortality risk Model algorithm • Postulates existence of “decision windows” • Assess current size and potential for future growth as parr • Assess expected fitness if smolt/mature at current size • Compare with expected fitness of growing to a larger size and making an optimal decision in the future • (discount for mortality) • For now, concentrate on females

4. Timing is everything… (thanks to D. Swank) Age 0 Age 1 Age 2 Age 3 Age 4 Age 5 rainbow Birth 1.1 smolt-1 1.2 1.3 freshwater parr 1.4 rainbow mature resident parr ? 2.1 smolt-2 2.2 smolt immature ocean 2.3 mature ocean rainbow maturity decision smolt decision 3.1 smolt-3 3.2 3.3

5. Timing is everything… (thanks to D. Swank) Age 0 Age 1 Age 2 Age 3 Age 4 Age 5 rainbow Birth steelhead smolt-1 rainbow freshwater parr steelhead smolt-2 mature resident parr rainbow smolt steelhead smolt-3 ocean steelhead rainbow steelhead smolt-4 maturity decision smolt decision . . .

6. Timing is everything… (thanks to D. Swank) Age 0 Age 1 Age 2 Age 3 Age 4 Age 5 rainbow Birth steelhead smolt-1 rainbow freshwater parr steelhead smolt-2 mature resident parr rainbow smolt steelhead smolt-3 ocean steelhead rainbow steelhead smolt-4 maturity decision smolt decision X

7. Timing is everything… (thanks to D. Swank) Age 0 Age 1 Age 2 Age 3 Age 4 Age 5 rainbow Birth steelhead smolt-1 rainbow freshwater parr steelhead smolt-2 mature resident parr rainbow smolt steelhead smolt-3 ocean steelhead rainbow steelhead smolt-4 maturity decision smolt decision

8. Timing is everything… (thanks to D. Swank) Age 0 Age 1 Age 2 Age 3 Age 4 Age 5 rainbow Birth steelhead smolt-1 rainbow freshwater parr steelhead smolt-2 mature resident parr rainbow smolt steelhead smolt-3 ocean steelhead steelhead smolt-4 maturity decision smolt decision

9. Dynamic State Variable model • F(l,g,e,t) • F: expected lifetime fitness • l: size • g: developmental switch, maturity • e: developmental switch, smolting • t: time • G(l,g,e,t) - future size at time t+1 • s(t) - survival to time t+1

10. Dynamic State Variable model • F(l,b,g,e,t) • F: fitness • l: size at t = end of window • b: size at start of window • g: developmental switch, maturity • e: developmental switch, smolting • t: time • G’(l,b,g,e,t) - updated future size

11. Terminal reward - Spawning • Latest possible spawning: F(l,g,e,Tsf) = (l) if g=1, F(l,g,e,Tsf) = 0 otherwise

12. Terminal reward - Spawning • Latest possible spawning: F(l,g,e,Tsf) = (l) if g=1, F(l,g,e,Tsf) = 0 otherwise • Earlier spawnings: F(l,g,e,ts) = (l)+s(t)F(G(l,g,e,ts),g,e,ts+1) if g=1, F(l,g,e,ts) = s(t)F(G(l,g,e,ts),g,e,ts+1) otherwise

13. Terminal reward - Emigrating F(l,g,e,te) = (l) if e=1, F(l,g,e,te) = s(t)F(G(l,g,e,te),g,e,te+1) otherwise F(l,g,e,t) = s(t) F(G(l,g,e,t),g,e,t+1) Updating - Outside Windows

14. Terminal reward - Emigrating F(l,g,e,te) = (l) if e=1, F(l,g,e,te) = s(t)F(G(l,g,e,te),g,e,te+1) otherwise F(l,g,e,t) = s(t) F(G(l,g,e,t),g,e,t+1) Updating - Outside Windows

15. Maturity Decision Window F(l,b,g,e,tdg) = s(t) maxg( F(G’(l,b,g,0,tdg),g,e,tdg+1)) if g=e=0, F(l,g,e,tdg) = s(t) F(G’(l,b,g,e,tdg),g,e,tdg+1) otherwise.

16. Maturity Decision Window F(l,b,g,e,tdg) = s(t) maxg( F(G’(l,b,g,0,tdg),g,e,tdg+1)) if g=e=0, F(l,g,e,tdg) = s(t) F(G’(l,b,g,e,tdg),g,e,tdg+1) otherwise. F(l,b,g,e,tde) = s(t) maxe( F(G’(l,b,0,e,tde),g,e,tde+1)) if g=e=0, F(l,g,e,tde) = s(t) F(G’(l,b,g,e,tde),g,e,tde+1) otherwise. Smolting Decision Window

17. Inputs: Survival and Growth • Survival: CJS MARK-recapture model • Pit tagged fish recapture rates • Separate analysis of YOY vs older fish • Seasonal but not yearly variation • Biased low - confounded with emigration

18. Inputs: Survival and Growth • Survival: CJS MARK-recapture model • Pit tagged fish recapture rates • Separate analysis of YOY vs older fish • Seasonal but not yearly variation • Biased low - confounded with emigration • Growth • Energy balance, optimal foraging • Temperature dependencies and allometries from literature, gut capacity and BMR from lab fits

19. Coastal Growth Valley Growth

20. Coastal Growth Model Comparison with Data

21. Life History Predictions - Coast smolt mature wait smolt wait

22. Life History Predictions - Coast “No” residents

24. Life History Predictions - Coast Many age 1 smolts > age 2 emigrants, a few older

26. Coastal Growth - Estuary Effects Hayes et al TAFS

27. Life History Predictions - Coast Threshold size of ~110mm in late December

29. Evidence for smolt threshold?

30. Evidence for smolt threshold?

31. Life History Predictions - American • “All” smolt as YOY and emigrate age 1 • Threshold size of ~150mm in late December • (higher threshold than coast) mature smolt wait

32. Predictions - Mokelumne • Most smolt as YOY and emigrate age 1 • Potential for slow growers to mature as parr mature smolt wait

33. Effects of changing environment • Short term: compare new growth vs. old thresholds (no response to survival changes) • Coast: much faster growth could yield mature parr. Easy to change average age at smolting.

34. Effects of changing environment • Short term: compare new growth vs. old thresholds (no response to survival changes) • Coast: much faster growth could yield mature parr. Easy to change average age at smolting. • Valley: slow growth might yield mature parr. Need to preserve good growth environment in late summer.

35. Effects of changing environment • Short term: compare new growth vs. old thresholds (no response to survival changes) • Coast: much faster growth could yield mature parr. Easy to change average age at smolting. • Valley: slow growth might yield mature parr. Need to preserve good growth environment in late summer. • Long term: • Both: Most sensitive to emigration survival • Importance of estuaries, passage through delta

36. Future directions • Bet-hedging • Explicit estuarine state and decisions • Refine functional relationship between temperature, flow, and growth • Males

38. smolting decision window time of emigration Decent chance of survival. Extra benefit from another year’s growth outweighed by river mortality, generation time. Size Too small to stand much chance of survival Time

39. smolting decision window time of emigration Decent chance of survival. Extra benefit from another year’s growth outweighed by river mortality, generation time. Size Too small to stand much chance of survival Time

40. smolting decision window time of emigration Decent chance of survival. Extra benefit from another year’s growth outweighed by river mortality, generation time. Size Too small to stand much chance of survival Time

41. coast valley Beakes et al. in prep