Intensive Monitoring of a Rearing Spring Chinook Cohort in the Little Wenatchee River, Columbia Basin, Washington

The Wenatchee River is a significant tributary to the Columbia River in north central Washington that supports extensive spawning and rearing habitat for ESA-listed populations of spring Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss).  The Integrated Status and Effectiveness Monitoring Program (Bonneville Power Administration Project 2003-017; ISEMP) has been evaluating status and trends of these populations basin-wide since 2001.  In 2014, ISEMP initiated an intensive monitoring study in the Little Wenatchee River, one of five major spring Chinook spawning areas.  The objectives of this study were to contribute towards parameterizing a life cycle model, and inform future study designs.  The study incorporated six sample events spread across nine months in order to track a full term of rearing occupancy for a single brood year cohort.  Fish were captured and PIT-tagged through an 11km reach during each sample event.  Estimated parameters include parr survival, habitat use and fidelity, growth, emigration patterns, fine- and broad-scale movement, carrying capacity and population abundance.  Project results suggest that this study design was likely more intensive than necessary to yield defensible estimates, but provided more precise and less biased estimates than previous site based sampling strategies.