Ecological, Geographic, and Genetic Differentiation and Management Units of Chum Salmon Oncorhynchus keta of the Southern Kuril Islands

Six ecogeographic units are verified in chum salmon Oncorhynchus keta (Walbaum, 1792) that spawns in the rivers of Iturup and Kunashir islands based on the zoogeographical zoning: of the physical-geographical regions of their spawning, certain ecological forms (ecotypes), and genetic differences between them. These are lake chum salmon of Lake Sopochnoe, river chum salmon from the basins of the Reidovaya and Kurilka rivers (Iturup Island), and river and lake forms of chum salmon of the Kunashir Island. The river chum salmon of Rybatskaya River (Iturup Island), eligible for protection due to its genetic uniqueness, is defined as a special (sixth) ecogeographic unit. These ecogeographic units are finally verified via assessment of their differentiation on the basis of DNA markers. In addition, the chum salmon of the Kuibyshevka River basin, water bodies north of Vetrovoe Isthmus, and those in the southern portion of the island should possibly be classified as additional ecogeographic units; however, their genetic features are understudied, which hinders their reliable verification. All listed ecogeographic units as a whole can be viewed as basic management units for the chum salmon of the southern Kuril Islands. The lake ecotype of Kuril Islands is liable for protection and careful approach to fishery and reproduction as a unique form of chum salmon of the Far East.