Genetic Structuring and Conservation of Asian Sockeye Salmon: Identification of Regional Stock Complexes

In order to describe large-scale spatial structure of Asian sockeye salmon the variability of 45 SNP loci was analyzed in 22 samples from the North-West coast of the Pacific Ocean. Three large regional population complexes were identified: southwestern Kamchatka, Kamchatka River basin, and the North-East (comprising stocks from Koryak Highlands). Populations within the identified complexes are connected by gene migration and have a common origin, close geographic proximity, comparable climatic, landscape and environmental conditions in the freshwater and early marine periods of life. Populations confined to watersheds of the North coast of the Sea of Okhotsk (Palana and Okhota rivers), along with island populations, displayed noteworthy distinctions from the isolated population complexes. We hypothesize that the marked divergence observed in island populations is primarily caused by genetic drift occurring during long periods of isolation. The pronounced divergence of Palana River population may be the result of both genetic drift and natural selection, driven by the challenging smoltification and juvenile transition to the ocean, along with local adaptations during spawning and early life periods in the Palansky Lake. At the same time in the Okhota River population, demographic factors such as genetic drift and bottlenecks played a key role.