1. Understanding sockeye salmon production in the Kvichak
Ray Hilborn thanks to T. Quinn for data and ideas, Tyler Dann and Wes Larson for genetics

2. Counting Tower

6. What causes the cyclic dominance?
Depletion of food in lakes
Increase in predators
Disease
Depensatory fishing
Substock structure

7. Recruits per spawner
Calculate how many adult fish return from the ocean for every fish that spawned
You need to know the number of spawners
counted at the counting tower, the catch in each year, and the age composition of the catch and escapement
If you have less than 1 recruit per spawner there is no sustainable yield

11. Maybe there are two curves, one when ocean conditions are good and one when they are bad

12. Productivity in Markov Model
Relative Productivity

13. Habitats Rivers and streams Island beaches Mainland beaches
Spring fed ponds

16. Quinn’s observations Island beach populations have greatly diminished
Island beaches have lower recruits per spawner than other habitats

17. Slim Morstad 2014 Kvichak manager for last 15 years
“I don’t want to put more than 3 million fish up the Kvichak because they just don’t seem to do well”

18. The hypothesis
Island beaches have lower egg to fry survival than rivers, streams and mainland beaches
Island beach stocks have been depleted
Increased escapements in the absence of island beach stocks will encounter carrying capacity limits and not be able to produce very large runs
Island beaches have much larger potential spawning area than other habitats
Rebuilding island beach stocks is required to produce very large runs

19. Estimates returns per escapement to five Iliamna Lake spawning sites (Brood Years 1958 – 1982, Blair 1989).
From T. Quinn

20. Why Island Beaches have lower survival
Fish in rivers rely on water flow to aerate the eggs and alevins
Fish on mainland beaches rely on underground water flow to do the same
Island beaches rely on wind driven currents, much more subject to vagaries of weather, ice cover, and warming lake temperatures
Note that beach spawner production was much better in cold times

21. The hypothesis
Island beaches have lower egg to fry survival than Rivers, streams and mainland beaches
Island beach stocks have been depleted
Island beaches have much larger potential spawning area than other habitats
Increased escapements in the absence of island beach stocks will encounter carrying capacity limits and not be able to produce 20+ million runs
Rebuilding island beach stocks is required to produce 20+ million fish

22. Where the fish spawn Aerial Surveys

26. Analysis of air survey data

27. A model of aerial counts
C y,s = T y p s .
The observed count in a year and site is a total number that where visible in the year (Ty) times the proportion of fish that go to each site (ps)

28. Genetics data from Kvichak catch confirm air counts proportions

29. This allows us to estimate the total number of fish in Island Beaches (blue) and for rivers and streams (orange)

30. The proportion in Island Beaches has declined dramatically

31. The p’s
Woody
Triangle Isl
Porcupine

32. The hypothesis
Island beaches have lower egg to fry survival than Rivers, streams and mainland beaches
Island beach stocks have been depleted
Increased escapements in the absence of island beach stocks will encounter carrying capacity limits and not be able to produce the big runs
Island beaches have much larger potential spawning area than other habitats
Rebuilding island beach stocks is required to produce 20+ million fish

33. Where are the River Fish?
% of fish
Area (1000 sq m)
Copper River
17%
412
Newhalen River
15%
3,065
Iliamna River
12%
2,000
Tazimina River 8%
163
Gibraltar Creek 9% 66
Lower Talarik Creek 6% 29

34. A general rule of thumb for sockeye salmon
1 spawning fish per square meter of good river habitat

35. Potential River Habitat
2-4 million spawners in good habitat
Admittedly a bit of a handwave but clearly the fish don’t “like” the big Iliamna and Newhalen rivers as much as they do Copper, Gibraltar, Tazimina, and Lower Talarik

36. The hypothesis
Island beaches have lower egg to fry survival than Rivers, streams and mainland beaches
Island beach stocks have been depleted
Increased escapements in the absence of island beach stocks will encounter carrying capacity limits and not be able to produce very largeruns
Island beaches have much larger potential spawning area than other habitats
Rebuilding island beach stocks is required to produce 20+ million fish

37. How much Island beach habitat is there?

38. From Kerns and Donaldson 1968

39. Total area (1965)
That is 1.3 million square meters with 3 million fish
1965 Estimate is that there were 10 million Island beach spawners

40. A quick calculation of area
If the surveyed sites had 3 out out of 10 million fish, then perhaps there are 4 million square meters of Island beach habitat capable of having densities of 2 fish per square meter

41. The hypothesis
Island beaches have lower egg to fry survival than Rivers, streams and mainland beaches
Island beach stocks have been depleted
Increased escapements in the absence of island beach stocks will encounter carrying capacity limits and not be able to produce very large runs
Island beaches have potential spawning area than as large or larger than other habitats
Rebuilding island beach stocks is required to produce very large runs

42. A two stock life history model 2nd stock has lower survival than 1st stock

43. The low survival stock disappears

44. Flies in the ointment

45. Non island habitat has returned large runs
Year
Total Return
%Island
Non Isl Return
1965
48,627,305
66%
16,447,183
1980
37,931,680
23%
29,078,010
1970
34,839,685
40%
20,816,793
1995
28,422,825
17,123,522
1979
24,927,042 9%
22,581,566

46. The aerial count sees 9% of the tower count

47. Explanations for missing fish
Not all spawning sites surveyed
Not all fish are in the rivers when surveys are done
Visibility of fish is less than 1
1965 comparison between on water counts and air counts for Woody and Porcupine beaches showed water count was twice aerial count

48. The research agenda
Redo brood tables with most recent data for individual types of habitat
Understand the capacity of each
Understand why aerial surveys see such a small portion of the fish
On water calibration studies
Understand amount and quality of Island beach habitats
Explore environmental changes on Island beach survival (wind, temperature, ice etc).

49. More research How to rebuild Island beach spawners?
Is there differential run timing?
Genetic composition of catch and escapement data
Is there potential for selective fishing based on size?
What harvest strategy could rebuild Island beaches, at what cost to yield?

50. Final research thoughts
The role of Island beaches cannot be considered in isolation of the two other critical Kvichak issues
What causes the period changes in productivity?
Understanding cyclic dominance

51. A final note
Island beaches have produced over 20 million sockeye salmon in a given year
This habitat is, in effect, one of the largest two sockeye population in the world
It appears to be severely depleted and almost commercially extinct
It probably qualifies as endangered under ESA

52. The End

53. Study questions What do we mean by recruits per spawner
Why do island beach spawning fish have lower recruits per spawner
Why are island beach spawning fish genetically different from river and stream spawners
What explanations are possible for the fact that the aerial counts only see about 9% of the fish counted past the counting tower
Can the production of the Kvichak sockeye population be sustained without Island beach spawning fish? Explain in two or three sentences.