Abundance of Puget Sound Steelhead near the turn of the 20th century

2. Abundance of Puget Sound Steelhead near the turn of the 20th century estimated from commercial catch data Nick Gayeski Wild Fish Conservancy March 14, 2012

3. Historical abundance of Puget Sound steelhead, Oncorhynchus mykiss, estimated from catch record data Authors: Nick Gayeski, Bill McMillan, Pat Trotter Canadian Journal of Fisheries and Aquatic Sciences, vol. 68, pp. 498-510, March 2011

4. Project Objectives Estimate abundance of Puget Sound steelhead based upon: Commercial catch data for the year of peak catch – 1895 Historical data regarding regional development to estimate unreported steelhead catch

5. Provide a robust historical baseline of PS steelhead abundance to serve as a reference for recovery so as to avoid the ‘shifting baseline syndrome’ Illustrate how quantitative data can be integrated with qualitative (historical) data to estimate historical abundance while fully accounting for the uncertainty of such estimates

6. Commercial Catch Data: Available for Five Populations Nooksack Skagit Stillaguamish Snohomish The remaining rivers and streams in Puget Sound

8. 1895 Commercial Catch Data (lbs) Nooksack 660,160 lbs. Skagit 205,190 lbs. Stillaguamish 180,000 lbs. Snohomish 401,620 lbs. Remaining PS 518,582 lbs. TOTAL 1,965,552 lbs.

9. Methods 1. Start with reported commercial catch in lbs. 2. Estimate the weight of steelhead in the catch 3. Estimate the unreported catch (tribal, sport, settlers/agricultural) as a proportion of the reported catch From 1- 3 , estimate the total numerical catch Estimate the total harvest rate on the 1895 run represented by the estimated total catch Do this in a way that accounts for all uncertainties in the estimation procedure

10. Bayesian Analysis The uncertainties are accounted for by employing a Bayesian analysis First, we obtain a distribution of the estimated total numerical catch, T: T = C*(1+U)/W (eq. 1), where C = commercial catch in lbs. U = unreported catch (% of reported) W = average weight of steelhead (lbs.)

11. Steelhead weight and unreported catchas a proportion of reported catch Weight 7 - 9.5 pounds Nooksack 0.10 – 0.30 Skagit 0.50 – 1.00 Stillaguamish 0.50 – 1.00 Snohomish 0.50 – 1.00 Remaining PS 0.50 – 1.00

12. Estimation of the Numerical Catch Randomly draw a large number of values of U and W (10 million) and Apply equation (1) to each. Cumulated values in bins of fixed width to build a histogram of T.

13. Distribution of Total Catch (Snohomish)

14. Estimation of the Terminal Run Place a distribution on harvest rate, R, and on total run size, N and calculate P(T|N,R) =(N!/(T!*(N-T)!) *TR*(N-T)(1-R) (eq. 2) Equation 2 is calculated for 10 million random values of R and N, and the values of T.

15. Harvest Rate Priors Nooksack: uniform(0.6, 0.9) Skagit: uniform(0.3, 0.6) Stillaguamish: uniform(0.4, 0.7) Snohomish: uniform(0.4, 0.7) Remaining: uniform(0.4, 0.7)

16. Terminal Run Size Priors Nooksack: uniform(80000, 225000) Skagit: uniform(50000, 200000) Stillaguamish: uniform(40000, 130000) Snohomish: uniform(90000, 290000) Remaining: uniform(100000, 370000)

17. Snohomish Prior and Posterior Distributions of Run Size

18. Snohomish Posterior and Prior Distributions of Harvest Rate

19. RESULTS

20. Total Catch Estimates Population Mean Mode SD Cntrl. 90th%-ile Nooksack 96800 91300 9700 81700 -- 113500 Skagit 43900 43300 5300 35000 -- 53100 Stilly. 38500 37700 4700 31100 – 46600 Snohomish 85900 83700 10400 69500 -- 104300 Remaining 110800 109000 13500 89400 – 134500 TOTAL 375900 365000 43600 306700 – 452000

21. Total Run Size Estimates Population Mean Mode SD Cntrl. 90th%-ile Nooksack 132600 127800 20400 101400 – 169000 Skagit 105600 86700 24700 70000 -- 149000 Stilly. 73700 69200 14900 51700 – 100000 Snohomish 164500 153000 33400 114000 -- 224000 Remaining 212100 185000 43100 148000 – 287700 TOTAL 688500 621700 136500 485100 – 929700

22. Harvest Rate Estimates Population Mean Mode SD Cntrl. 90th%-ile Nooksack 0.74 0.60 0.09 0.61 – 0.88 Skagit 0.43 0.31 0.09 0.31 -- 0.58 Stilly. 0.54 0.42 0.09 0.41 – 0.68 Snohomish 0.54 0.42 0.09 0.41 – 0.68 Remaining 0.54 0.40 0.09 0.41 – 0.68 Grand Mn. 0.56 0.40 0.09 0.43 – 0.70 Mn (Totals) 0.55 0.59 NA 0.36 – 0.63

23. Comparison to Current Conditions Two methods of comparison Compare estimated turn-of-century abundance to NOAA status review estimates for 1980 - 2004 and for 2000 – 2004 Compare estimates scaled to estimates of lengths of stream accessible to adult winter-run steelhead (fish-per-kilometer)

24. Current Conditions

25. Historical Estimates

26. FKM for Recent Average and Estimated Historical Abundance

27. Fish-Per-Accessible Stream Km for Historic PS and Situk 1952

28. CONCLUSIONS Current abundance is 1% to 4% of the estimated turn-of-century abundance Habitat currently accessible to adult winter-run steelhead is no less than 67% of what was available at the turn of the century It is unlikely that habitat loss can explain the majority of this historic decline. This may indicate that significant recovery is still in the cards!

29. Severe impairment of both ecosystem and autecological function Steelhead have lost significant life history and genetic diversity Interactions with hatchery fish and loss of salmon abundance in addition to habitat loss and simplification are plausible culprits

30. Thank You for Your Attention!