Pacific rim population structure of Sockeye salmon as determined from microsatellite analysis

The Pacific Rim population structure of sockeye salmon Oncorhynchus nerka was examined with a survey of microsatellite variation. Variation at 14 microsatellite loci was surveyed for over 48,000 sockeye salmon sampled from 299 localities ranging from the Columbia River to Japan. The value of the genetic differentiation index F IT over all populations and loci was 0.097; individual locus values ranged from 0.038 to 0.154. Sockeye salmon from the Queen Charlotte Islands and the Columbia River displayed the least number of alleles relative to sockeye salmon from other regions in the Pacific Rim distribution of the species. Conversely, sockeye salmon displaying the greatest allelic diversity were observed in Southeast Alaska and the central coast of British Columbia. Sockeye salmon from these two regions displayed approximately 30% more alleles than did sockeye salmon from the Queen Charlotte Islands and the Columbia River. Sockeye salmon from Russia and western Alaska were, on average, less diverse than sockeye salmon from Southeast Alaska and more southerly locations in North America. A regional structuring of populations was generally observed among the sockeye salmon populations sampled, and populations were clustered within lakes and river drainages. At the Pacific Rim scale of population structure, there were two major groups of populations. The first group included populations from Russia, Bristol Bay, Kodiak Island, the Alsek River, and the Queen Charlotte Islands. The second group generally included populations from Southeast Alaska, British Columbia, and Washington. The distribution of microsatellite variation of sockeye salmon on a Pacific Rim basis reflected the origins of sockeye salmon radiating from refuges after the last glaciation period.