Coho Salmon Population Structure in North America Determined from Microsatellites

Abstract

AbstractPopulation structure of coho salmon Oncorhynchus kisutch from Russia to California was examined with a survey of microsatellite variation to describe the distribution of genetic variation. Variation at 17 microsatellite loci was surveyed for approximately 50,000 coho salmon sampled from 318 localities. The genetic differentiation index (FST) over all populations and loci was 0.058, with individual locus FST values ranging from 0.027 to 0.143. The least genetically diverse coho salmon were observed from Russia, the Porcupine River in the Yukon River drainage, and the middle Fraser and Thompson rivers in southern British Columbia. Coho salmon from Vancouver Island, British Columbia; Puget Sound, Hood Canal, and Juan de Fuca Strait, northern Washington; and Oregon displayed the greatest number of alleles compared with coho salmon in other regions. Differentiation in coho salmon allele frequencies among regions and among populations within regions was approximately seven times greater than that of annual variation within populations. A regional structuring of populations was the general pattern observed; coho salmon spawning in different tributaries within a major river drainage or spawning in smaller rivers in a geographic area were generally more similar to each other than to populations in different major river drainages or geographic areas. The distribution of microsatellite variation in coho salmon likely reflects the origins of salmon radiating from refuges after the last glaciation period.