Discriminating coho salmon (Oncorhynchus kisutch) populations within the Fraser River, British Columbia, using microsatellite DNA markers

Three microsatellite loci were used to examine genetic variation among 16 coho salmon (Oncorhynchus kisutch) populations within the Eraser River drainage system, in British Columbia, Canada. Each locus was highly polymorphic with 30 alleles at the Ots101 locus, 15 alleles at the Ots3 locus and 38 alleles at the Ots103 locus. Average observed heterozygosities were 86.1%, 70%, and 56.1%, respectively. With the exception of the Dunn and Lemieux River populations, Chi-square tests and F-ST values indicated that all populations had significantly different allele frequencies. Two distinct population groups within the Eraser River drainage were observed. Lower Eraser River populations were strongly differentiated from populations spawning in the upper Eraser River, which includes the Thompson River (a tributary flowing into the upper Eraser) and the portion of the Eraser River beyond the precipitous Eraser River canyon. This regional population structure may have resulted from colonization of the upper and lower Eraser River regions by different founder populations following Pleistocene glaciation, and be maintained by adaptive differences between the two groups of coho salmon. Coho salmon populations in the upper Eraser and Thompson River drainages form an evolutionarily significant unit (ESU) of importance for conservation of biodiversity in coho salmon. Microsatellite DNA loci show promise as technically simple and highly informative genetic markers for coho salmon population management.