Graduation Date

Summer 2020

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Dr. Andrew Kinziger

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Darren Ward

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. David Hankin

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Fisheries

Abstract

Distinct populations of steelhead in the wild are in decline. The propagation of steelhead in hatcheries has been used to boost population numbers for recreational fisheries and for use in conservation. However, hatchery breeding practices of steelhead can result in changes in genetic structure. I investigated the genetic structure of winter-run steelhead (Oncorhynchus mykiss) returning to the Mad River, California, where a hatchery has been used enhance production for recreational fisheries since 1971. Genetic variability in Mad River steelhead was evaluated using 96 single nucleotide polymorphisms (SNPs) among 4203 individuals, including the Mad River and nearby locations, and spanning 44 years from 1973 to 2017. I resolved evidence that in the 1970s the Mad River contained both an indigenous population, and a population influenced by the introduction of Eel River winter-run broodstock. Even with the introduction of Eel River broodstock, contemporary Mad River steelhead (1983-2017) appear to be distinct from Eel River collections, as well as other surrounding collections (except Redwood Creek). This distinction is a consequence of the presence of a historically unique population in the Mad River, combined with the inability of the initially introduced Eel River steelhead broodstock to establish itself. Lastly, I found that contemporary Mad River Hatchery broodstock are composed of three groups (or broodlines), defined by adult return year (1) 2009, 2012, and 2015, (2) 2010, 2013, and 2016, and (3) 2011 and 2014. Grouping in 3-year intervals is hypothesized to be a result of the predominant usage of age-3 individuals as broodstock at Mad River Hatchery.

Citation Style

American Fisheries Society

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