Genetic differentiation of chum salmon in Alaska influenced by glacial history

Abstract

One major goal of fisheries management is to ensure the sustainable harvest of wild populations so that productivity is stable over time. Information on population structure is necessary for effective fishery management because it helps describe the appropriate spatial scale for management units, and can identify populations that are small or isolated and need protection from overharvest. Chum salmon (Oncorhynchus keta) is a species targeted by both commercial and subsistence fisheries. Estimating fine-scale population structure of chum salmon in Alaska is of increasing concern because of fluctuating census sizes, and the uncertain effects of bycatch on specific populations.In this study we examined the genetic structure of 66 chum salmon populations spawning in waterways on the Alaska Peninsula and Kodiak Island. This area was covered by the Cordilleran Ice Sheet 25,000 years before present, and spawning habitats were unavailable for salmon at this time. Thus, colonization of the region by salmon occurred relatively recently. We found that chum salmon populations on the Alaska Peninsula and Kodiak Island contain considerable genetic diversity for the species. Patterns of differentiation appear to be influenced by the geographic distance separating populations, glacial history of the region, and time since colonization. The fine-scale genetic data that we have assembled will be useful to fisheries managers as they continue to evaluate the impacts of bycatch and monitor the long-term productivity of chum salmon populations.