Population structure of chum salmon <i>Oncorhynchus keta </i>in the Russian Far East, revealed with microsatellite markers
Chum salmon populations in the Russian Far East have a complex multi-level genetic structure. Fifty-three samples (2446 fish) were grouped into five major regional clusters: the southern Kurils, eastern Sakhalin, southwestern Sakhalin, the Amur River, and a northern cluster. The northern cluster consists of chum salmon populations from a vast geographical region, including Chukotka, Kamchatka, and the continental coast of the Sea of Okhotsk. However, the degree of its genetic differentiation is low, 1.9%. In contrast, the southern population cluster exhibits a much higher variation; for example, differentiation between chum salmon groups within Sakhalin Island reaches 4.6%, and differentiation between Iturup Island versus Sakhalin Island chum salmon is 7.7%. This suggests that southern populations of Asian chum salmon have a more ancient evolutionary history than northern populations. In contrast to the available data, our study indicates a great deviation of southwestern Sakhalin populations from the rest of Sakhalin chum salmon. The Russian Far East chum salmon are genetically diverse and show statistically significant differentiation even within small geographic localities. This can be used to assign samples of unknown origins to definite local populations.