Data on the regional composition of mixed marine aggregations of juvenile pink salmon during postcatadromous migrations in the basin of the Sea of Okhotsk in 2022 are demonstrated. A high probability of a significant predominance is revealed for pink salmon spawning returns 2023 of the northern stock complex compared to the southern ones. Identification estimates for juvenile fish obtained from RFLP analysis of mtDNA and analysis of allelic variability of SNP loci are compared to the values of actual regional catches and spawning returns. Close correspondence between the calculated estimates and actual data on the results of the 2023 fishing season was noted. Forecast about predominance of pink salmon of the northern stock complex, as well as about atypically low proportion of fish from water bodies of Iturup Island is fully confirmed. The estimates for Sakhalin Island and the southern part of the continental coast of the Sea of Okhotsk are close to the actual catch.

Polymorphism of 10 nuclear microsatellite loci in coho salmon populations in the Asian part of the range was studied for the first time. Three genetically distinct regional stock complexes were identified: Kamchatka, northern part of the Sea of Okhotsk and Sakhalin. It was shown that all populations, regardless of their geographic location, are characterized by a high level of genetic polymorphism.

Sockeye salmon genetic diversity in the Kuril Islands (Iturup, Urup, Paramushir, Shumshu) and the Commander Islands (Bering Island) was examined on 7 microsatellite loci. Average estimates of the heterozygocity observed on different loci vary from 0.300 to 0.858. General estimate of genetic differentiation θ_st is 15%, with a 95% confidence bootstrap interval [10.40–21.18%]. The results obtained in the program BOTTLENECK 1.2.02 made it possible to identify the passage of the “bottle neck” by all island populations. Unique properties and significant differences from each other are shown for allfivчe populations examined. The level of sockeye salmon intrapopulation diversity found in the Kuril and Commander Islands is significantly lower compared to that in the continental water bodies, what is generally typical for marginal populations of the species range.

Chum salmon sample from the catches of autumn trawl surveys in the Sea of Okhotsk (2016–2021), including individuals with otolith marks of Japanese salmon hatcheries (SHs), was analyzed based on microsatellite loci polymorphism. Reference database of eight microsatellite loci frequencies, created before and included 26 samples of chum salmon from major reproductive regions in the Sea of Okhotsk basin, has been updated with data on the microsatellite allele variety of chum salmon from Hokkaido and Honshu. Result s of the research indicate of strong similarity between chum salmon of the Kuril Islands and individuals released from Japanese SHs.

Results of analyzing the spawning sockeye salmon age structure, length-weight composition and absolute fecundity are demonstrated for the Ozernaya River stock. In the course of maturation the sockeye salmon individuals can return into the Ozernaya River for spawning in the ages 3+, 4+, 5+, 6+ or 7+. A positive trend has been figured out for relative abundance of the 5+ and 6+ sockeye salmon individuals and generation abundances, a negative trend – for the 4+ individuals. Negative dynamics has described for the averaged length-weight indices and the mean absolute fecundity of sockeye salmon of the Ozernaya in the research period. Patterns of changes in biological indicators of the fi sh depending on density factors in the period1971–2020 have been identified.

The  fishery and some aspects of the biology of the Pacific ocean perch  Sebastes alutus  off the Commander Islands. It has been established that the harvest of this species is episodic in nature, is not subject to seasonal dynamics and is carried out in a local area located west of the Bering Island. The contribution of this water area to the total catch of rockfishes in the Petropavlovsk-Commander subzone in 2001–2022 did not exceed 26.5%. Near the Commander Islands, S. alutus  was observed at depths of 138–370 m at a water temperature near-bottom of 3.1–3.9°C, and in catches it was represented by individuals 17–45 cm length. Presumably the formation of accumulations in the upper part of the continental slope to the west of the Bering Island is due to the presence of an anticyclonic circulation, which contributes to the formation of high concentrations of zooplankton as the main food source and favorable conditions for the development of spawned larvae.

Occurrence of marine mammals in different types of  fisheries and interactions between marine mammals and fisheries in the Okhotsk and Bering Seas and the Pacific waters adjacent to the eastern coast of Kamchatka and the Kuril Islands was analyzed. Classification of marine mammal species on their dependence from the fisheries has been made.