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Steelhead in Idaho

A comparison of juvenile life histories among selected Snake River steelhead populations Brett Bowersox, Timothy Copeland, and Alan Byrne Idaho Department of Fish and Game. Steelhead in Idaho. Present in Snake, Clearwater, and Salmon River drainages Provide valuable fishery

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Steelhead in Idaho

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  1. A comparison of juvenile life histories among selected Snake River steelhead populationsBrett Bowersox, Timothy Copeland, and Alan ByrneIdaho Department of Fish and Game

  2. Steelhead in Idaho • Present in Snake, Clearwater, and Salmon River drainages • Provide valuable fishery • Well documented variation in ocean life history (A vs B run) • High variation in freshwater habitat characteristics • Freshwater life history not extensively studied in Idaho • ESA listed in 1997

  3. ESA Status Assessments • Abundance • How many of them are there? • Productivity • How well do they reproduce & survive? • Spatial structure • Where are they? • Diversity • What are they like?

  4. Technical Recovery Team Efforts • No population specific data • Used aggregate A-run, B-run data for adults at Lower Granite Dam • Divided abundance to population within run-type • Assumed all had same run-type productivity • Limited information on life history or spatial structure

  5. Objectives • Compare/contrast freshwater life history data • Examine implications for population productivity

  6. Study Populations East Fork Potlatch River Big Bear Creek Crooked Fork Creek Fish Creek Rapid River

  7. Technical Recovery Team Populations Lower Clearwater (A-run) Lochsa (B-run) Little Salmon (A-run)

  8. Environmental Variation

  9. Methods • Use 2008 emigrant data from screw traps • Abundance, scale samples, PIT tags • Metrics • Emigrant abundance • Timing from natal stream • Age composition • Length at age • Detections in Snake/Columbia hydrosystem

  10. Objective 1 • Compare/contrast freshwater life history data

  11. 2008 Abundance Estimates

  12. Seasonal Outmigration Variability Spring Summer Fall

  13. Age Distribution Age -0 Age -1 Age -2 Age -3 Age -4

  14. Length at Age

  15. Detection rates in Hydrosystem • Spring tags detected in year of tagging (Sp 2008) • Summer and fall tags detected year after tagging (Sp 2009)

  16. Objective 1 Summary • A variety of life history strategies observed between the populations • Juvenile rearing completed within natal streams and downstream reaches • Lower elevation populations have younger age structure than high elevation

  17. Objective 2 • Examine implications for population productivity

  18. Relative Productivity Model • Use abundance, age structure, & assumed survival to estimate initial fry abundance • Use abundance & apparent migration survival to LGD to estimate smolt production • Productivity measure is smolts per fry

  19. Fry to Smolt Survival • Survival Relative to Big Bear Creek in parentheses

  20. Objective 2 Summary • Productivity differences within Technical Recovery Team populations • (Fish Cr v. Crooked Fk / Big Bear v. EFK Potlatch) • Decreasing natal stream survival increases relative advantage of Big Bear & EFK Potlatch • B-run populations need increased smolt-adult survival & fecundities to make up for older age structure

  21. Summary • Variation in freshwater life history important to population stability • Low elevation populations very resilient • Results similar to genetic & parr density studies • High “value” of habitat restoration projects for lower elevation populations • Further investigations of high elevation & Salmon River populations

  22. Questions

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