Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7651
Title: Genetic Population Structure of Willamette River Steelhead and the Influence of Introduced Stocks
Author: Donald M. Van Doornik, M. A. Hess, M. A. Johnson, David J. Teel, Thomas A. Friesen, James M. Myers
Publication Year: 2015
Journal: Transactions of the American Fisheries Society
Volume: 144
Pages: 150-162
DOI: 10.1080/00028487.2014.982178
Keywords: Oncorhynchus mykiss,Genetics

 Conservation genetics studies are frequently conducted on Pacific salmon (Oncorhynchus sp.) to delineate their population structure and to quantify their genetic diversity, especially for populations that have experienced declines in their abundance and are subject to anthropomorphic activities.  One such group of salmonids is steelhead (O. mykiss) from the Willamette River, a tributary of the Columbia River.  Within the Willamette River there are multiple steelhead life history and run timing types, some of which originated from non-native populations. Late winter-run steelhead and rainbow trout (the freshwater resident type of O. mykiss) are native to the Willamette River, whereas early winter-run and summer-run steelhead have been introduced into the system via releases from artificial propagation efforts.  We conducted genetic analyses of Willamette River steelhead to determine their genetic population structure with regard to the effect that non-native steelhead released into the Willamette River basin have had on the native steelhead.  We found genetic differentiation among the samples that separated them into four population groupings that corresponded to run type.  Possibly due to local adaptation, the native run type has retained its genetic distinctiveness from the introduced types, despite there being opportunities for gene flow among them.  Introduced early winter-run steelhead appear to be the origin of steelhead inhabiting certain Willamette River tributaries where native steelhead did not historically spawn.

Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.