Chum salmon is a widely spread species on the continental coast of the Okhotsk Sea presented exclusively by typical anadromous phenotype. Abundance of the runs is well correlated with length of the spawning rivers, whereas dynamics of the runs is determined by variations of climate conditions and press of commercial fishery. Detailed data on geographic and temporal structure of the species are presented, as the summarized data on timing and dynamics of the spawning migration and information on geographic and interannual variability of biological parameters of the spawners.

Feeding of mass fish species caught in the Obutonai River (Sakhalin, Nevelsk district) was examined in May-July 2021, in the time of downstream migration of natural pink salmon Oncorhynchus gorbuscha juveniles and release of chum salmon O. keta juveniles from a fish hatchery. Three fish species capable to predate on salmon juveniles were presented in the catches in significant number, as whitespotted char Salvelinus leucomaenis, pacific redfin Tribolodon brandtii, and juveniles and dwarf males of masu salmon O. masou. These species occurred in different lower reaches of the river. Whitespotted char fed by both pink and chum juveniles, but was relatively few in number (single mass catch). Two-year-olds and dwarf males of masu salmon fed less intensively and pacific redfin fed exceptionally rarely on the migrating pink salmon juveniles of natural origin, but both these species consumed actively the chum juveniles released from a hatchery. The masu salmon juveniles had the maximum abundance in early June, then their number decreased. The pacific redfin abundance had complicated dynamics because of migrations both from the upper part of the river and from the sea; pacific redfin spawned in late June when ate exclusively eggs of the same species.

The northwestern Bering Sea, in particular the waters at Cape Navarin, is one of the main areas of the walleye pollock fishery. Environmental variability in the Bering Sea affects on recruitment, abundance, behavior, and seasonal spatial distribution of pollock, which challenge on the fishery management strategy. Understanding of environmental-driven changes in the pollock population has to improve predictions of the population dynamics and affect positively on the commercial harvest. The pollock from the eastern Bering Sea migrate to the Navarin area in summer-fall season. This study demonstrates that great annual differences in the migration activity, spatial distribution of pollock and fishery are related with oceanographic conditions, zooplankton productivity, the population reproduction, year-classes abundance and total biomass. Appearance of the relatively abundant year-classes in 2017–2020 may lead to some increase in commercial part of the pollock population in 2022–2024.

Coho salmon is a common object of ichthyofauna in the water bodies of the continental coast of the Okhotsk Sea, with the main stocks concentrated in the central part of the region. The species exhibits mostly the anadromous life strategy in the ontogenesis, though the resident groups are known in three lakes located in the basins of Inya, Ul’beya and Okhota Rivers. Temporal structure of anadromous coho salmon is demonstrated for the first time within the region: the stock is presented by two forms, as early and late ones. Spawning runs of these forms could be indicated by changes of qualitative parameters of fish. Coho salmon of the early and late forms reproduce on spawning grounds with different hydrological and thermal regimes. Juvenile coho salmon spend from 1 to 3 years in the fresh water before the seaward migration. Duration of marine period of their life is usually 1 year, but rarely they return for spawning either in the year of seaward migration or after two winters in the sea. Variability of abundance and qualitative parameters of coho salmon is conditioned mainly by environments of reproduction and feeding, with some impact of epigenetic difference in size and age between the life strategies in ontogenesis.

Spatial distribution patterns and abundance of arctic cod Boreogadus saida are considered for the southwestern Chukchi Sea on the data of acoustic surveys and trawl samples obtained by TINRO research vessels in 2003–2020. The highest abundance and biomass of this species indicated by the echosounder–measured backscattering coefficient s_A (m² per sq.n.mile) were observed in August 2003, decreased significantly in 2007–2008 and later, with the minimum in 2010, increased in 2014 due to the high portion of juveniles, but continued to decrease in recent years and reached the lowest value in 2020. This negative tendency for arctic cod contradicts to the walleye pollock abundance increasing in the southwestern Chukchi Sea on the background of warming in the Arctic. The arctic cod were distributed mainly in the northeastern and southwestern parts of the surveyed area, usually as vast fields of small schools or sparse layers. To the east from 174°W, the aggregations were formed by large-sized fish distributed mostly at the bottom. In the western area, the aggregations were formed within thermocline at the depth of 10–20 m or had two–layer structure with the juveniles dominated in the upper layer and larger fish at the bottom. Typical echograms showed dense schools of arctic cod with the height up to 30 m and horizontal size of 120–400 m, presumably formed by migrating fish. Diurnal vertical migrations were not expressed for this species, though the aggregations of lower density were observed at night, in general, with some local aggregations of permanently dense schools, both in the daytime and at night.

On example of walleye pollock at East Kamchatka, one of possible approaches is considered to assess the state of stocks for marine commercial species with usage of the data on age structure in catches. Algorithms for suboptimal filtering and interpolation (extended Kalman smoother and unscented Kalman smoother) are presented for a cohort model of an exploited stock, in presence of uncertainty about true value of the vector of the system parameters.

 Distribution of 211 species and larger taxa of benthic animals is considered along the gradient of chemical contamination in bottom sediments (by TPF index) on the data of long-term observations (1992–2019), using hierarchical Hausman-Olf-Fresco logistic regression models. Frequency of occurrence and density in settlements are used as the quantitative measures of the macrozoobenthos distribution. Parameters of the species relation to contamination are determined, as mean coordinate of the response curves, position of the optimum, and width of the outer and central niches. By these parameters, using the fuzzy sets algorithm, the taxa are classified to five groups: i) extremely sensitive; ii) highly sensitive; iii) moderately tolerant; iv) tolerant; and v) extremely tolerant to pollution (ES, S, MT, T and ET, respectively). Both stenobionts, steno-eurybionts and eurybionts are presented in each group, but the stenobionts dominate in ES and S groups and the eurybionts prevail in T and ET groups, being the opportunists of the II and I order, while the taxa of different biontity are equally presented in MT group. The classification could be used for interpretation of changes in composition and structure of macrozoobenthos in the areas subjected to anthropogenic pollution.

Species composition, structure, density and biomass of macrobenthos in the estuary of the Manuy River are described, its main communities are defined and their trophic characteristics, production, and distribution along the river channel are determined on the materials collected in July 2021. Three main biotopic zones of the estuary are identified by their hydrological features and parameters of macrobenthos: the river mouth, the lower estuary, and the upper estuary. Bilateral structure of salinity with 0.8–5.0 psu in the upper layer and > 27 psu near the bottom was observed in the lower estuary, whereas the upper estuarine zone was filled mostly by oligohaline water (0.8–1.6 psu), with only a thin refugial layer of the seawater (23.1 psu) at the depth of 0.9 m. In total, 24 species of benthic invertebrates and cyclostomes were presented in the macrobenthos. The species richness varied insignificantly across the estuary, from 4 species/section in its upper part to 9 species/section in the lower part, with lowered richness at the border between the lower and the upper estuarine zones, that corresponded to the theory of critical salinity. The density of macrobenthos distribution decreased from the river mouth to the boundary between the lower and upper zones (from 808.0 ± 162.0 ind./m² to 16.0±2.8 ind./m²), then increased sharply in the upper estuary (up to 1384 ± 160 ind./m²). The total biomass had two peaks: in the lower estuary (4.381 ± 0.589 g/m²) and in the upper estuary (up to 28.950 g/m²), with the minimum of 0.076 ± 0.015 g/m² between. The boundary between the meso-, polyhaline lower estuary and the oligohaline upper estuary had the width of several hundred meters. Four benthic communities were identified by various methods of cluster and ordination analysis, regardless of the method: two communities in the upper estuary (communities of Eogammarus kygi and Neomysis awatschensis), one community in the lower estuary (community of Hediste japonica) and the community of Haustorioides at the river mouth. Gathering detritivores formed the basis of biomass and macrobenthic production at the river mouth; collecting detritophages — sestonophages were the most significant in the lower estuary; while three key trophic groups were presented in the upper estuary: 1) collecting detritivores — macrogrinders — scavengers, 2) collecting detritivores, and 3) ground feeders — collecting detritivores. Daily production of macrobenthos was low at the river mouth and in the lower part of the lower estuary but increased in its upper part and in the upper estuary.

Artificial reproduction of pacific salmon in the Russian Far East, as a rule, is carried out with gross violations of scientific recommendations. Perhaps, that’s why positive and negative effects of the salmon farming largely neutralize each other. The following paradox is noted for the Far-Eastern basin: the salmon catches decrease in the areas where fish farming is active but increase in the areas where the salmon reproduction is almost completely provided by natural spawning grounds. Fishery, conservation of natural populations, and artificial reproduction of fish juveniles are still separate and disconnected spheres in Russia, largely due to general state of the national salmon economy.

Results of experimental growing of japanese scallop Mizuhopecten yessoensis in the first three years of life in cages mounted in the Aniva Bay (southern Okhotsk Sea) are presented. Mean size and weight of the mollusks are determined and their growth rate and survival are compared with these indices for juvenile scallops from natural settlements in the Aniva Bay and other habitats located in the Far East region. Feasibility of the cage method for commercial cultivation of the scallop in conditions of the Aniva Bay is concluded.

Antiradical activity of water-soluble components of tissues is investigated for 26 species of marine organisms belonged to 7 classes: Bivalvia, Cephalopoda, Malacostraca, Holothuroidea, Asteroidea, Echinoidea, and Actinopterygii. Molecular weight of the proteins and peptides was measured in the water extracts using the modular liquid chromatograph (Agilent Technologies 1260 Infinity, USA) with UV detection at 280 nm in TSK gel column G 3000PWXL 7.8 mm I.D. × 30 cm (TOSOH Corporation, Japan) under flow rate of 0.3 mL/min and temperature of 25^о C. All samples were twice prepared and double measured. The mobile phase consisted of 0.1 N NaCI 20 mM Tris-HCI buffer with pH 7.8. The following standard protein samples were used as a reference for the molecular weight measurement: bovine serum albumin (MW 66.3 kDa), egg albumin (44.3 kDa), myoglobin (18.0 kDa), cytochrome C (12.4 kDa), aprotinin (6.5 kDa), and bacitracin (1.4 kDa) (Sigma-Aldrich Co., USA). All samples were filtered before injection through 0.2 µm syringe filter (Whatman, PVDF). Molecular weight of peptides was calculated by the elution time. Scavenging effect on DPPH free radical was measured by Molyneux method and on ABTS radical – by the method proposed by Re et al. The maximum antiradical activity (measured by mg of ascorbic acid per 1 g) was found for the tissue of Patiria pectinifera (5.21), its various values were determined for the tissue of bivalve mollusks (Corbicula japonica, Mercenaria stimpsoni, Spisula sachalinensis, and Glycymeris yessoensis — 5.10; 1.15; 1.36 and 1.08, respectively) and medium values — for gonads of Strongylocentrotus intermedius and S. nudus (2.18 and 2.21, respectively). The amount of proteins and peptides with low molecular weight (1–5 kDa) correlated well with the radical scavenging activity (Pearson correlation coefficient 0.801, r² = 0.642).

Safety indices, size-weight structure, and chemical composition of the muscle tissue and liver are determined for a small-sized shark species as spurdog Squalus boretzi caught with longline in the area of Imperial Ridge seamounts (North-West Pacific). The highest catch was recorded on Koko Rise at the depth of 700 m. The sharks had the body length from 55 to 94 cm and the weight of 830–4540 g. Content of proteins and lipids in the muscle tissue (24.8 % and 0.8 %, respectively) of spurdog corresponds to low-calorie high-protein fish. The proteins contain all the essential amino acids in the ratio close to an «ideal protein». The lipids are presented by mainly phospholipids (57 % of total amount). The portion of polyunsaturated fatty acids in the lipids is 46.6 %, including 36.9 % of omega-3 fatty acids. The sum of biologically significant fatty acids (eicosapentaenoic and docosahexaenoic) reaches 34.7 %. The shark liver contains about 83 % of lipids, mostly monounsaturated fatty acids (53 % of total lipid amount) and 20.6 % of PUFA. The amount of biologically significant fatty acids (EPA + DHA) in the liver is about 10.5 %. In terms of hygienic and microbiological parameters, the muscle tissue of Squalus boretzi meets the requirements of Euro-Asian Union (№ 040/2016) and Customs Union (№ 021/2011). However, a heightened content of mercury is found in the liver of spurdog that makes difficult to use this source of valuable lipids.

Results of implementation of the Concept for development of fisheries in the Russian Federation until 2020 are considered. Of the 16 tasks, 3 (19 %) were fully implemented, 7 (44 %) were partially implemented, and 6 (37 %) were not implemented.