Genetic Studies in the Yakima River Basin Yakima/Klickitat Fisheries Project Monitoring and Evaluation Annual Report 2001-2002

摘要

We examined the population genetic structure of steelhead (Oncorhynchus mykiss) collected from different locations in the Yakima River basin (Roza Dam, Ahtanum Creek, Toppenish Creek, and Satus Creek). The primary objectives of this study were to assess spatial and temporal patterns of genetic diversity within and among these populations. To address our objectives, we used microsatellite DNA markers to analyze steelhead populations from four localities that were sampled in 2000 and in 2001. We generated multilocus genotypes for 753 individuals (371 from 2000 and 382 from 2001) using ten highly polymorphic microsatellite loci. Our results revealed significant population genetic structure among the collections with reduced genetic differentiation between years. Of 28 pairwise tests of genotypic differentiation, only the 2000 and 2001 Roza Dam collections and the 2000 and 2001 Satus Creek collections did not exhibit significant differences. Similarly, pairwise tests of genetic differentiation (FST) were significant for all comparisons except the between-years comparisons of Roza Dam, Toppenish Creek, and Satus Creek collections. All tests between populations sampled from different localities were significant, regardless of the collection year, indicating that these collections represent genetically differentiated stocks with little or no gene flow among them. While our results revealed strong geographic population structure with limited temporal structure among populations of steelhead, samples from additional localities (for example, the Naches River and its tributaries) are needed for a more comprehensive assessment of steelhead population structure in the Yakima River basin.