FEATURES OF GENETIC-STRUCTURE OF COHO SAL MON (ONCORHYNCHUS-KISUTCH WALBAUM) POPULATIONS

Data on genetic variation in five Asian populations of coho salmon are presented. Average heterozygosity estimated for 22 loci (0.0026) was the lowest of all Pacific salmon species. It is assumed that genetic v ariation in coho salmon decreased during glaciation periods due to a d ecrease in population size and corresponding increase in genetic drift in the few surviving populations. Resettlement of coho salmon from th ese populations in climate-warming periods largely determined the gene tic composition of modern populations of this species. Total heterozyg osity in coho salmon populations may be higher, but, in this case, it is determined by allelic diversity of genes, different from those in o ther salmonid species.