Snake River steelhead Management goals

1. Snake River steelhead Management goals Rishi Sharma Columbia River Intertribal Fish Commission Portland, OR

2. Overview of the talk • Stock status. • Pre and Post Dam effects (1976 cut-off). • Assessment of optimal spawning stock size. • Assessment of SAR and its effect on optimal spawning stock size. • Rebuilding targets and in river management. • Conclusions.

8. Dam effect Where R=recruits, S=spawners and t is equal to 0 for the years before the completion of Lower Granite Dam (1976) and 1 after.

9. 1968 was Lower Monumental • 1972 was Little Goose dam • 1975 was Lower Granite

11. Conclusions from dam analysis • We can’t mix data from pre and post 1976 (LGR was completed in 1975). • For rebuilding reference point’s we decided to use the pre 1976 data and use two models, the Beverton-Holt and the Ricker model. • Performed an analysis to use both models using Bayesian inference.

12. Assessing Uncertainty in Parameter estimates (adult data)

13. Assessing Uncertainty in Parameter estimates (juvenile data)

15. Conclusions from this analysis • Fit using the adult data was extremely poor (r2 was less than 0.1) • Decided we should use the juvenile data. • However, how do we assess smolt to adult return (SAR) in our adult management goal? • Simulated 4 SAR’s (encapsulating both passage and climate induced return rates) using observed smolt data and low, average, highest and rebuilding survival estimates. • Re-ran the analysis on adults simulated and used both models with an integrated goal.

17. Goals based on varying survival (passage and ocean/climate effect) • Low survival (17,000, CV=0.8). • Medium survival (21,000, CV=0.9). • Highest ever observed survival (27,000, CV=0.12). • Rebuilding target based on return rates from the Keogh River in BC (60,000, CV=0.11)

18. Rebuilding and Fish Management 101

19. Implicit assumptions for rebuilding • Juvenile productivity is high. • Increase passage survival (adult mortality on average through the dams (14-60% mortality through dams for adult stage). • As long as SAR is low, management targets need to be low. • Rebuilding can only be attained through improving survival and/or increasing available habitat.

20. Overall conclusions • Dams had an effect on productivity pre and post 1975. • Current management targets should not be greater than 27,000 adults. • Rebuilding target of 60,000 adults can be attained through increasing productivity and/or capacity. Functions are different depending on which model we choose to use. • Aggregated goals for all Snake River steelhead are probably biased low, but the data resolution is unavailable at the sub-species or sub-population level.

21. Acknowledgements • Henry Yuen, USFWS my co-author in this work. • David Graves, CRITFC for the GIS based maps. • Charlie Petrosky, IDFG for sharing his juvenile data with us. • Technical Advisory Committee (TAC) for checking the validity of the data. • Dr. Nate Mantua and Dr. Bob Francis for influencing me to think about climatic effects on management goals.