Document Type


Date of Degree Completion

Spring 2024

Degree Name

Master of Science (MS)



Committee Chair

Paul James

Second Committee Member

Clay Arango

Third Committee Member

Andrew Murdoch


Effective management of fish populations in inland waters requires, at the most fundamental level, a basic understanding of population abundance. This is especially important for critically depressed species having high conservation value. Unfortunately, due to their critically depressed abundance, the anadromous form of Oncorhynchus mykiss, known as Steelhead Trout, has high conservation value in the upper Yakima Basin located in central Washington State. However, the resident form of O. mykiss, known as Rainbow Trout, are numerous in the watershed. We used a juvenile tagging study coupled with a long-term population monitoring study to disaggregate this mixed O. mykiss population into its respective life history components. Our results were spatially explicit providing a method to identify areas of relatively high anadromous production throughout our basin. Our evaluation suggests that upper Yakima tributary streams exhibit greater anadromous output than does the larger mainstem Yakima River which has limited restoration potential due to water allocation commitments. We conclude that under current conditions, fruitful O. mykiss restoration strategies might consider actions maximizing migrant survival to and from the marine environment coupled with instream restoration actions that diversify stream habitats and facilitate the expression of multiple life history pathways, thereby, maximizing resiliency in this population.

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Biology Commons