Friend or Foe Influence of Resident Trout on

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 Jay Vaughan, CFS Tommy Garrison, CFS Steve Cramer, CFS Funding Yakima Basin Joint Board

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

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

Photo Credit David Child

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

0. 709 87 Sr : 86 Sr 0. 708 0. 707 0. 706 0. 705 0. 704 0. 703 0 500 1000 1500 2000 Microns 2500 3000

0. 710 87 Sr : 86 Sr 0. 709 0. 708 0. 707 0. 706 0. 705 0. 704 0. 703 0 500 1000 1500 Microns 2000 2500 3000

Photo Credit Frank Thrower

ce dan ate bun on R nt A ributi t ide Res nt Con ide Res nce unda b A d a e Steelhead Resilience

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.