Multiple Pleistocene glaciations significantly affected the gene pool of many species inhabiting the Northern part of the Pacific Rim, an area with a rich glacial history. This paper is devoted to the study of intraspecific polymorphism of the coho Salmon and the routes of its settlement throughout the Asian part of its range. Such problems are traditionally solved by comparing parts of the mitochondrial genome. Here, two fragments of mtDNA, the control region (D-loop) and the cytochrome b gene (cytb), were investigated. It was shown that the settlement of the Asian Pacific coast by the coho Salmon was preceded by a chain of successive migration events from the refugium located on the North American continent to the South of the ice sheet covering the area of modern Canada and southern Alaska. The low level of genetic polymorphism in Asian coho populations seems to be a result of a pronounced founder effect, rather than being characteristic of the species as a whole.
