Importance of Habitat in salmon declines and recovery

1. Importance of Habitat in salmon declines and recovery Ray HilbornSchool of Aquatic and Fishery SciencesUW

2. What is wrong with salmon?The 4-H’s • Harvest • We take too many • Habitat • We degrade their streams • Hydroelectric • We block passage, turn rivers into lakes • Hatcheries • We try to “mitigate” for habitat loss by artificial production

3. Structure of talk • Trends in abundance • How bad is the problem • Ocean conditions – the BIG driver • Hydroelectric • Harvest • Hatcheries • Habitat

4. Myth IWe are running out of wild salmon The “truth”: there are nearly as many wild salmon in western North America now as any time since Europeans arrived But: this due primarily to Alaska, and in the Lower 48 many stocks are extinct and most are well below historical levels

5. Bristol Bay wild sockeye

8. Puget Sound Coho Wild Returns

9. A B C 400 Run Size 300 200 100 D E F Year Chinook salmon past Bonneville Dam

10. Myth IIThe ocean is big, unlimited and salmon abundance is driven by freshwater and habitat The “truth”: most large scale variation in salmon abundance is driven by ocean changes But: this only means it is harder to detect anthropogenic impacts

11. 8 Sediment chemistry 7 6 Mixing model Sediment 15N (‰) 5 30 4 20 Salmon density (1000s/km2) 12 reference lakes 10 Sockeye population 8 0 2 4 6 8 10 Sediment 15N (‰) 4 Salmon density (1000s/km2) sockeye 0 1750 1750 1800 1800 1850 1850 1900 1900 1950 1950 2000 2000 Year Historical sockeye population dynamics Lake Nerka, SW Alaska Schindler and Leavitt (2001)

12. Historical sockeye population dynamics Lake Nerka, SW Alaska 12 Salmon density (1000s/km2) 8 4 0 1750 1800 1850 1900 1950 2000 Year + fishery catch escapement Schindler and Leavitt (2001)

13. 12 8 4 0 6 4 Diatoxanthin (nmol/g) 2 0 12 8 4 Lutein-zeaxanthin (nmol/g) 0 1750 1800 1850 1900 1950 2000 1750 1800 1850 1900 1950 2000 Year Effects of sockeye population on phytoplankton production Sockeye (1000s/km2) Sockeye density Algal pigments in lake sediments Schindler and Leavitt (2001)

14. Survival rate by Realm Fallchinook Springchinook Coho Arctic SE Alaska Coastal BC Georgia Strait Puget Sound Coastal Washington Columbia Basin Coastal Oregon California Avg survival rate

15. Coho survival rate by Domain Survivalrate Release year

16. Fall chinook survival rate by Domain Survivalrate Release year

17. Spring chinook survival rate by Domain Survivalrate Release year

18. Coho survival~SST regression

19. Coho survival~SST regression (incl. resid)

20. Gulf of Alaska – Small set of structuring variables operating at different speeds - Whammo!

21. Myth IIIThe decline of NW salmon is due to dams The “truth”: systems without dams have had similar trends But: clearly dams are not good for salmon and are part of the problem

24. Chinook survival by river segment B: Columbia below dams W: Willamette River A: Columbia above dams S: Snake River L: Lower Fraser T: Thompson River U: Upper Fraser Fall chinook Spring chinook Fall chinook 100% 100% 10% 10% 1% 1% Survival rate 0.1% 0.1% 0.01% 0.01% 0.001% 0.001% L T U B W A S B W A S Columbia Columbia Fraser

25. Chinook survival in Columbia Basin Spring chinook Fall chinook Survival rate Survival rate

26. Chinook survival in Fraser Basin Fall chinook Survival rate

27. Myth IVHatcheries are necessary to mitigate for lost of habitat and over-harvest The “truth”: hatcheries have strong negative impacts on wild salmon But: if we eliminate hatcheries we might have no salmon left in some places

28. Hatcheries • The basic assumptions • Freshwater habitat is limiting • Egg to smolt survival in the wild is about 5% • Hatcheries can usually obtain 80% egg to smolt survival • Release smolts ready to go to sea – they don’t need any freshwater habitat

29. Why hatcheries were built • To compensate for over-harvesting • To compensate for habitat destruction • To mitigate for dam impacts • To buffer natural variation • To provide extra fish for harvest • To conserve threatened stocks

33. Did Hatcheries Work • We have over 300 hatcheries in the Pacific Northwest • “If hatcheries were the solution, we wouldn’t have a problem!” • Much disagreement, what would have happened without hatcheries

35. Concerns about hatcheries • Generate over-harvesting on wild fish in mixed stock fisheries • Compete with wild fish in freshwater and ocean • Introduce and exacerbate diseases • Genetically degrade wild fish by domestication and hybridization • Provide an excuse to allow habitat loss

36. Pink salmon hatcheries in Prince William Sound • Largest hatchery program in North America • 600 million fish stocked each year • Competing hypotheses re marine fish stocking • stocking augments wild production • stocking replaces wild production • We have BACI !!!!!!

37. Prince William Sound salmon production

38. Total return

39. Wild fish production

41. Myth VThe collapse of salmon in the late 80s and 90s is due to habitat changes The “truth”: habitat has not changed that much But: habitat is definitely declining

42. Few (if any) attempts to integrate all factors in combined analysis • We have detailed harvest models • We have no hatchery impact models in use • Changes in ocean conditions are being better understood but not used in evaluating recovery plans • A number of habitat models, EDT the most used

43. Framework for impact of habitat • Multi-stage life history model from Moussalli and Hilborn 1986 • each life history stage as a Beverton-Holt curve with a productivity (initial slope or survival) and a capacity • Key question is how to relate habitat to productivity and capacity

44. Sharma coho carrying capacity

45. Key Model ComponentsSHIRAZ • Spatially explicit – reaches or estuarine areas • Life stages as many as you want • Stocks may be life histories, wild/hatchery etc • Capacity and productivity – any life history • Habitat characteristics by reach • Stochastic factors (flows, ocean survival etc) • Functional relationships between habitat characteristics and stochastic factors and productivity and capacity

46. Reach Characteristics • Passage • Square meters spawning gravel • Distance • Square meters rearing habitat • Percent fines in gravel • Watershed area by reach • Percent impervious by reach • Temperature, DO etc.

47. Functional relationships • Spawning gravel and egg capacity • % fines in gravel and egg to fry survival • Up the the user to define what you want to use • Will ultimately build a “library” of functional relationships much like EDT … • But the user will decide which ones to use from the library

48. General model framework • Read in the data • reach-specific habitat • hatchery input • Functional relationships • Hatchery practice • Harvest and ocean conditions specification • habitat interventions • Loop over time • Calculate the change in habitat • Calculate the change in population size • End the loop

49. Habitat Changes • Annual habitat change: habitat degradation • Habitat change due to a 1-time event: habitat restoration

50. Hatchery Influence • Affect wild fish through competition • Interbreeding can cause domestication of wild fish, and reduced survival