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Friend or Foe? Influence of Resident Trout on Steelhead Production in the Yakima Basin

Friend or Foe? Influence of Resident Trout on Steelhead Production in the Yakima Basin. Ian Courter Cramer Fish Sciences. David Child. Acknowledgements. David Child, DC Consulting Jim Hobbs, UC Davis Chris Frederiksen , YN Joe Blodget , YN Dave Fast, YN Shadia Duery , CFS

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Friend or Foe? Influence of Resident Trout on Steelhead Production in the Yakima Basin

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  1. Friend or Foe? Influence of Resident Trout on Steelhead Production in the Yakima Basin Ian CourterCramer Fish Sciences David Child

  2. Acknowledgements David Child, DC Consulting Jim Hobbs, UC Davis Chris Frederiksen, YN Joe Blodget, YN Dave Fast, YN ShadiaDuery, CFS Jay Vaughan, CFS Tommy Garrison, CFS Steve Cramer, CFS Funding Yakima Basin Joint Board

  3. Background • Use existing data to determine whether resident rainbow trout contribute to the upper Yakima Basin steelhead population • Construct a steelhead population dynamics model that accounted for conspecific resident rainbow trout

  4. Model Validation 350 Observed Predicted (default parameterization) 300 Predicted (no Rf smolt production) 250 200 Steelhead Spawner Abundance 150 100 50 0 1992 1994 1996 1998 2000 2002 2004 2006

  5. Photo Credit David Child

  6. Hypotheses A significant number (≥10%) of resident rainbow trout offspring migrate to the ocean and return as adult steelhead.

  7. 0.709 0.708 Sr 0.707 86 0.706 Sr : 87 0.705 0.704 0.703 0 500 1000 1500 2000 2500 3000 Microns

  8. 0.710 0.709 0.708 Sr 86 0.707 Sr : 0.706 87 0.705 0.704 0.703 0 500 1000 1500 2000 2500 3000 Microns

  9. Photo Credit Frank Thrower

  10. Steelhead Resilience Resident Abundance Resident Contribution Rate Steelhead Abundance

  11. Conclusions O. mykiss populations in the Yakima Basin are partially anadromous, and significant numbers of offspring from resident trout adopt an anadromous life-history. 17% resident maternal origin 30% or more have at least one resident parent steelhead population viability and recovery is dependent on existence of a robust resident trout cohort, which highlights the importance of jointly managing freshwater and anadromous life-histories as units of the same population.

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