Genetic variation and population structure in masu salmon Oncorhynchus masou of Japan.

Abstract

Genetic variation and population structure among masu salmon river populations in Japan were examined. Enzymatic proteins in tissue samples of fish among twenty populations collected from eighteen rivers were assayed for electrophoretically detectable variants. 34 loci were tenta-tively identified, 17 (50.0%) of which were polymorphic. Significant differences in the frequencies of alleles were observed even among the proximal river populations. The magnitude of genetic divergence among masu salmon river populations is relatively large among Pacific salmon, On-corhynchus spp. While stability of allelic frequencies was observed between annual samples from same river systems. According to the resulting dendrogram, the examined populations appeared to be roughly divided into two geographic groups at the Shiretoko Peninsula of Hokkaido; (1) the rivers entering the Strait of Nemuro and the Pacific Ocean, (2) the rivers entering the Okhotsk Sea and the Japan Sea. The obtained level of the average heterozygosity of masu salmon was 5.2%.