The chum salmon, Oncorhynchus keta Walbaum, spawning in rivers and lakes of the Far East, is divided into ecogeographic units (EGUs) based on zoogeographic zoning of the species range, biological features of groups that take into account spawning areas and ecological forms (ecotypes), and genetic differences between them. Each EGU has definite geographical boundaries and can include several spawning populations of chum salmon from different water bodies within these boundaries. Populations of chum salmon from different EGUs have significant genetic differences between each other. Ecogeographic units are important elements of the intraspecific structure. They can also be considered as basic management units of chum salmon, which should be taken into account when developing a strategy for managing stocks of aquatic biological resources. In particular, in the process of artificial reproduction of this species, transfer of fertilized eggs between populations from different EGUs is highly undesirable.

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.

Using the example of chum salmon Oncorhynchus keta in the Amur zoogeographic province, we review the principle of subdividing the species into population groups. On the basis of zoogeographic zoning and biological boundaries of chum salmon groups defined by the spawning areas, taking into account the distribution, migration, and reproduction, as well as estimates of their differentiation using microsatellite DNA markers, we identified eight ecogeographic units in the Amur province. In the Amur zoogeographic region of this province, these included the summer chum salmon of the Amur-Amgun ecoregion and the autumn chum salmon of the Lower Amur (Amur-Amgun and Amur-Ussuri ecoregions); in the Shantar zoogeographic region of the province, the Uda-Tugur and Ulban groups; in the Sakhalin part of the Amur province, groups from the northwestern and northeastern Sakhalin, as well as summer and autumn chum salmon from the Poronai River. These ecogeographic units can be considered as basic spawning management units of chum salmon for this part of the species distribution range.

Using ten microsatellite loci, the analysis of genetic variability and differentiation of the Pacific herring Clupea pallasii over a wide geographic range in the Sea of Okhotsk, the Bering, Chukchi, Kara, Barents, and White seas was performed. A similar level of genetic variability is shown for the herring belonging to three geographical subspecies. The genetic structure at a large scale is most pronounced between the three geographical subspecies of herring, with the different level of genetic differentiation within each of the subspecies. Herring of the Pacific distribution range is differentiated only at the level of large basins, the Sea of Okhotsk and Bering Sea, which indicates a significant level of gene exchange, as in the southeastern part of the Barents Sea and in the Kara Sea. However, the gene flow in the White Sea herring is limited to a very small spatial scale.

The study includes 41 sample sets of chum salmon from the northern part of its geographic range analyzed at ten microsatellite loci. In the northern part of the range of Asian chum salmon, the following groups of samples are clearly distinguished: “Magadan oblast,” “Northern Kamchatka,” “Penzhina River,” and “Anadyr River basin.” Populations of chum salmon from the Apuka River and the “Koryak Upland” group show low genetic differentiation from other groups. There is a positive relationship between the latitude and the average expected heterozygosity in this part of the range. Chum salmon of the Penzhina River shows close genetic relationship to chum salmon from the Anadyr River basin, probably because of gene flow.

The genetic diversity of ten microsatellite loci is examined in samples of Arctic rainbow smelt. The expected heterozygosity estimates vary in the range of 12.6–83.9% (mean 55.3%). The degree of genetic differentiation is statistically significant: θ = 2.8%, 95% CI (1.4–4.9%). The greatest differences are found between datasets of smelt in Eastern and Western Kamchatka. The samples from Lake Nerpich’e demonstrate the maximum estimates of divergence from the other datasets from both the western and eastern coasts.

The genetic differences between the sockeye salmon populations of the Kamchatka Peninsula were studied. The time of divergence between the resident sockeye salmon, which are reproductively isolated in Lake Kronotskoye, and the anadromous sockeye salmon is estimated using data on microsatellite markers. A weak unidirectional gene flow is observed from resident sockeye salmon into the population of anadromous sockeye salmon spawning in the Kronotskaya River, which is a channel of Lake Kronotskoye. The obtained point estimate of the time of divergence between the resident and anadromous sockeye forms (ca. 10 000 years) is consistent with the geological estimates for the time of formation of the modern Kronotsky lake–river drainage basin. The conclusion was made that the resident sockeye salmon of Lake Kronotskoye originated from the anadromous sockeye salmon of Lake Paleo-Kronotskoye and formed under the conditions of the reproductive isolation from other sockeye populations and the loss of connection with the sea. The necessity for conservation of the Kronotsky resident sockeye salmon, which implies prevention of its mixing with anadromous sockeye salmon, is discussed.

The genetic variability of ten microsatellite loci was examined in samples of the herring from the Sea of Okhotsk and the Bering Sea. All loci were polymorphic; the expected heterozygosity estimates varied in the range of 0.3–94.3% (mean 66.7%). The degree of genetic differentiation of the herring was statistically significant (θ = 1.38%). The level of pairwise genetic differentiation FST was–0.002–0.046; RST was–0.003–0.166. Genetic differentiation of the herring from the Sea of Okhotsk and the Bering Sea correlated with the spatial-geographic structure of the species in the studied range on the basis of FST (P = 0.001).

The chum salmon of the Amur River (the mainland part of the Far East) and the Poronai River (Terpeniya Bay, Sakhalin Island) are historically related to one another, as the drainage basins of these rivers are the remnants of a formerly single river system, the Paleoamur, which existed when Sakhalin Island was a part of the continent. Both river populations of chum salmon consist of the early-run and late-run ecological forms (seasonal races), which are also referred to as the summer and autumn races. They are reproductively isolated from each other due to their spawning at different times and in different types of spawning grounds. To assess the direction, pattern, and degree of divergence between these chum salmon races in the both river fragments since the Paleoamur, it is necessary to compare them using two types of traits: selectively neutral DNA markers and morphological and physiological traits, variations in which may have an adaptive value. For this, we have studied chum salmon from both rivers in terms of microsatellite DNA markers, body counts and measurements, body weight, and fecundity. Both in the Amur River and in the Poronai River, the autumn race of chum salmon prevails over the summer race in body length and weight, fecundity, number of pyloric caeca, and several other meristic traits. The intra-basin differences between the races are much more pronounced in the Amur chum salmon. The inter-race differences in microsatellites are also greater in the Amur chum salmon compared to the Poronai chum salmon. Using microsatellites, three levels of differentiation have been revealed: (1) between the basins of the Amur and Poronai rivers, (2) between the races within each of the river basins, (3) and between population samples within each race of each basin. A hypothesis is proposed that the currently existing races of chum salmon in the Amur and Poronai rivers have evolved since the breakup of the Paleoamur, and the intra-basin divergence of the races started in the Amur River earlier than in the Poronai River. An analysis of our own data and the published data suggests that the adaptation of the seasonal races of chum salmon to the conditions of their spawning grounds is determined by a complex of morphological and physiological traits, including the number of pyloric caeca, which is an adaptive and highly heritable trait associated with the incubation temperature of the water.

The mechanisms of the adaptation of the Kildin cod to the conditions of a meromictic lake were analyzed based on the study of morphological, biological, and genetic characteristics. Significant differences between the Kildin cod and Atlantic cod have been found in their morphological and genetic characteristics. The results of an X-ray microanalysis of otoliths, which were conducted for the first time, confirm that the distribution range of the Kildin cod in Lake Mogilnoye also extends to brackish waters. It has been shown that the formation of the reproductively isolated lacustrine population of Kildin cod is accompanied by specialization in a number of characteristics (body color, feeding strategy, behavior, etc.) and by a decrease in genetic diversity.

In this study, 12 samples of chum salmon from the southern and central parts of Primorye were studied with ten microsatellite loci. All studied localities of chum salmon of Primorye formed three main genetically different groups: (1) the Narva–Barabashevka–Ryazanovka cluster of southern Primorye, (2) Kievka River, and (3) Avvakumovka River. The revealed genetic heterogeneity of chum salmon showed clear population structure in accordance with the geographical location of the samples. The study suggests that, for the purposes of artificial reproduction of chum salmon, it is desirable to perform egg planting with regard to the described population structure of chum salmon of Primorye.

This study focuses on the strategy for the conservation of masu salmon, Oncorhynchus masou , in the northern part of the species range (via the masu populations in Sakhalin Oblast), based on data of its population structure. It is shown that masu populations that inhabit different rivers genetically differ from each other in allele frequencies at microsatellite markers. In the Naiba River basin, at least two genetically distinct masu populations exist: in the upper reaches and in a tributary, the Bolshoy Takoy River. The masu populations on Iturup Island significantly differ from those on Sakhalin Island; within Sakhalin, the masu salmon from the Chernaya River in the southwestern part of the island is genetically distinct from the southeastern Sakhalin and Aniva Bay populations. The genetic diversity of Iturup populations is substantially lower than that on Sakhalin, probably due to their small sizes. The measures for the conservation and recovery of masu salmon populations should be based primarily on their own genetic resources, or, in the case of a lack of spawners, on the base populations of their ecological/geographical region. In the latter case, masu populations of large rivers can be considered as base ones: for southeastern Sakhalin, this is masu salmon of the Naiba River; for Aniva Bay, this is masu salmon of the Lyutoga River. Transplantation of fish, fertilized eggs, or any other genetic material from a population that is different genetically and inhabits the waters with different ecological gradients should be strongly restricted. The formosan masu salmon from Taiwan Island is studied as an example of a strict genetic isolate.