Dataset Information

The Impacts of Dam Construction and Removal on the Genetics of Recovering Steelhead (Oncorhynchus mykiss) Populations across the Elwha River Watershed.

ABSTRACT: Dam construction and longitudinal river habitat fragmentation disrupt important life histories and movement of aquatic species. This is especially true for Oncorhynchus mykiss that exhibits both migratory (steelhead) and non-migratory (resident rainbow) forms. While the negative effects of dams on salmonids have been extensively documented, few studies have had the opportunity to compare population genetic diversity and structure prior to and following dam removal. Here we examine the impacts of the removal of two dams on the Elwha River on the population genetics of O. mykiss. Genetic data were produced from >1200 samples collected prior to dam removal from both life history forms, and post-dam removal from steelhead. We identified three genetic clusters prior to dam removal primarily explained by isolation due to dams and natural barriers. Following dam removal, genetic structure decreased and admixture increased. Despite large O. mykiss population declines after dam construction, we did not detect shifts in population genetic diversity or allele frequencies of loci putatively involved in migratory phenotypic variation. Steelhead descendants from formerly below and above dammed populations recolonized the river rapidly after dam removal, suggesting that dam construction did not significantly reduce genetic diversity underlying O. mykiss life history strategies. These results have significant evolutionary implications for the conservation of migratory adaptive potential in O. mykiss populations above current anthropogenic barriers.

SUBMITTER: Fraik AK

PROVIDER: S-EPMC7828262 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Publications

The Impacts of Dam Construction and Removal on the Genetics of Recovering Steelhead (<i>Oncorhynchus mykiss</i>) Populations across the Elwha River Watershed.

Fraik Alexandra K AK McMillan John R JR Liermann Martin M Bennett Todd T McHenry Michael L ML McKinney Garrett J GJ Wells Abigail H AH Winans Gary G Kelley Joanna L JL Pess George R GR Nichols Krista M KM

Genes 20210113 1

Dam construction and longitudinal river habitat fragmentation disrupt important life histories and movement of aquatic species. This is especially true for <i>Oncorhynchus mykiss</i> that exhibits both migratory (steelhead) and non-migratory (resident rainbow) forms. While the negative effects of dams on salmonids have been extensively documented, few studies have had the opportunity to compare population genetic diversity and structure prior to and following dam removal. Here we examine the imp ...[more]

PMID: 33450806

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Project description:Genetic stock identification (GSI) is an important fisheries management tool to identify the origin of fish harvested in mixed stock fisheries. Periodic updates of genetic baselines can improve performance via the addition of unsampled or under-sampled populations and the inclusion of more informative markers. We used a combination of baselines to evaluate how population representation, marker number, and marker type affected the performance and accuracy of genetic stock assignments (self-assignment, bias, and holdout group tests) for steelhead (Oncorhynchus mykiss) in the Snake River basin. First, we compared the performance of an existing genetic baseline with a newly developed one which had a reduced number of individuals from more populations using the same set of markers. Self-assignment rates were significantly higher (p < 0.001; +5.4%) for the older, larger baseline, bias did not differ significantly between the two, but there was a significant improvement in performance for the new baseline in holdout results (p < 0.001; mean increase of 25.0%). Second, we compared the performance of the new baseline with increased numbers of genetic markers (~2x increase of single-nucleotide polymorphisms; SNPs) for the same set of baseline individuals. In this comparison, results produced significantly higher rates of self-assignment (p < 0.001; +9.7%) but neither bias nor leave-one-out were significantly affected. Third, we compared 334 SNPs versus opportunistically discovered microhaplotypes from the same amplicons for the new baseline, and showed the latter produced significantly higher rates of self-assignment (p < 0.01; +2.6%), similar bias, but slightly lower holdout performance (-0.1%). Combined, we show the performance of genetic baselines can be improved via representative and efficient sampling, that increased marker number consistently improved performance over the original baseline, and that opportunistic discovery of microhaplotypes can lead to small improvements in GSI performance.

Dataset Information

The Impacts of Dam Construction and Removal on the Genetics of Recovering Steelhead (Oncorhynchus mykiss) Populations across the Elwha River Watershed.

Publications

The Impacts of Dam Construction and Removal on the Genetics of Recovering Steelhead (<i>Oncorhynchus mykiss</i>) Populations across the Elwha River Watershed.

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