Sablefish is an endemic species of the North Pacific. Its range extends from California Peninsula, along the Pacific coast of the US and Canada to Aleutian Islands and further, along the Pacific coast of Kamchatka and the Kuriles to the central part of Honshu Island. They dwell also in the Bering Sea and southeastern Okhotsk Sea. Sablefish are the most abundant in the southeastern Bering Sea and in the Gulf of Alaska, that is conditioned by favorable conditions for their larvae and juveniles. In the Asian part of the range, the environments are generally more severe, and reproduction of sablefish is rather risky. Following to the results of modern genetic studies, the sablefish stocks are distinguished by high genetic homogeneity that suggests a common population with the main spawning grounds in the southeastern Bering Sea, at the Pacific coasts of Aleutian Islands, in the Gulf of Alaska, and at the coasts of British Columbia, Washington, Oregon and California. Dynamics of the sablefish biomass is considered on the data of bottom and midwater trawl surveys conducted by TINRO in 2003–2020, fishery statistics, and accessible data of NOAA (USA). Sharp increasing of the biomass and annual catches is noted both in the eastern and western Bering Sea in the last few years because of appearance of several strong year-classes. Western Bering Sea stock depends on migration of recruits from the common spawning grounds in the southeastern Bering Sea. For the western Bering Sea, two main ways of such migration are possible: i) active migration of juveniles with benthic habitat; and ii) passive transfer of pelagic larvae and early juveniles across the Bering Sea through the system of surface currents. The latter mechanism supports the sablefish recruitment in the bays of the western Bering Sea and, to a lesser extent, at the eastern coast of Kamchatka. Sablefish in the West Bering Sea fishery zone were caught in 2010–2020 mostly as by-catch for trawling and longline fishery (93 %), other 7 % were landed by specialized longline fishery. The basic points for managing the sablefish fishery in the West Bering Sea zone are defined. About 400 t of sablefish is permissible to catch annually in the West Bering Sea fishery zone in conditions of modern high stock of this species. This value includes 100–120 t that will inevitably be caught as by-catch and the rest of 280–300 t is a foreseeable resource for organization of specialized fishery.

Distribution and abundance of myctophid fish species in the upper epipelagic layer are analyzed based on results of surveys in the Gulf of Alaska in winters of 2019 and 2020. A common myctophid community driven by blue lanternfish Tarletonbeania crenularis was revealed that occupied likely the entire eastern part of the Subarctic Front zone eastward from 150ºW. Abundance and biomass of four mass myctophid species were generally comparable between the northeastern and northwestern Pacific. Small-sized juveniles prevailed among northern lampfish Stenobrachius leucopsarus, which were likely transported by the Subarctic Current and could be recruited to the Bering Sea stock. Patterns of daily vertical migrations are discussed for the mass myctophid species. New observations confirm general understandings on the myctophid species input to functioning of fish community.

Residence time of late-race sockeye spawners on spawning grounds located in the littoral zone of Lake Nachikinskoye in southern Kamchatka is determined directly using 11 series of tagging and tracking of tags conducted in 2018 and 2020 (700 tagged individuals). The residence time is the key parameter for calculation of the spawners number on the data of repeated observations from the beginning to the end of spawning. Methodology of the experiment is described in details and all data of measurements are presented. Impact of certain variables on the target function is discussed. The residence time is estimated as 5 days.

Effects of interannual fluctuations of sockeye salmon escapement to the spawning grounds on dynamics of sexual, age and length-weight structure of the population are demonstrated on generalized data of long-term observations in Lake Dalneye in 1939–2020. Mature sockeye specimens were caught in the Dalnaya River during their anadromous migration to the lake and analyzed by the authors, personally; archive and earlier published data were used, as well. The escapement was evaluated by visual assessment of the sockeye migrants entered to Lake Dalneye and confirmed by counting of mature individuals on the littoral spawning grounds in the lake. Number of dwarf sockeye salmon was estimated using the earlier found correlation between their stock and forage zooplankton biomass (Kurenkov, 1991; Pogodaev, Kurenkov, 2012). The zooplankton biomass was assessed on samples of zooplankton collected monthly at a stationary station in the central part of the lake (once a month during the ice period and up to three times per month during the ice-free period) from the layer 0–50/55 m by vertical towing of Juday plankton net (mouth diameter 18 cm). The numbers of anadromous sockeye males and females had ratio 1 : 1 in years with the maximum spawning stock, but < 1 : 1 when their returns to the lake decreased. Besides, the males were smaller in such years and the dwarfs (matured without migration to the sea) and jacks (matured with short marine period) were able to escape commercial fishing gears. Age of the spawners had a tendency to increase with decreasing of spawning runs and, conversely, more abundant runs were formed by younger spawners. Long-term pressure from fishery and selection of larger individuals caused the body length and weight decreasing for mature sockeye salmon, shortening of their period of marine feeding, and increasing of the smallsized males portion in the population.

Data on spatial distribution and habitat conditions are presented for walleye pollock Theragra chalcogramma at southern Kuril Islands in spawning season (spring 2015) and feeding season (summer 2016). In spring, walleye pollock are distributed over the entire shelf and continental slope down to 900 m depth and occupy the upper layer on the shelf and intermediate layer at the slope with water temperature 0.1–1.5 o C. In summer, they aggregate at the depth of 200–270 m beyond the shelf in the intermediate water at the Pacific slope of Iturup Island, under the temperature of 1.3–2.9 o C. Both spatial and bathymetric migrations of pollock are minimal at the Pacific side of Iturup, but they migrate for spawning westward and southwestward to the Okhotsk Sea and slope of Small Kuril Ridge where concentrate at the benthic front between the tidal mixing zone and the Intermediate water. Seasonal redistribution of walleye pollock is accompanied with changes of size-age structure in the main aggregations.

Generalized additive models are applied for standardization of daily landing per unit effort (LPUE) for opilio crab using the data of fishery statistics for the West Bering Sea fishery zone in 2003–2020. A set of 12 models with various combinations of predictors was examined and the best model with the smallest value of Akaike criterion was selected (information criterion Akaike 21743, explained variance 58.6 %). The selected model reflects the effect of depth, distance from the coast, daily effort and tensor product of geographic coordinates and day of the year. LPUE was standardized using the selected model by substituting median values of nominal predictors and modal values of categorical predictors. Then the crab stock was estimated using the state-space form of Deriso-Schnute delay-difference model. The estimates based on both standardized and nominal indices are compared and a significant difference between them is found: the stock is assessed as 23,040 t with nominal indices but as 17,070 t using the standardized indices.

Hematopoiesis is a mechanism of multifunctional adaptation in vertebrates, including fish. Adaptive capabilities of populations are studied for a species of genus Salvelinus with high ecological plasticity. Char Salvelinus malma is represented in Kamchatka by the anadromous, river, brook, and several lake forms. Peripheral blood cells are investigated for this species juveniles and adults from the Raduga River in the lower Kamchatka River basin. The fish sampled in August 2013 were divided into two groups: sexually mature individuals (10 specimens) and juveniles (10 specimens). The body length (AC) of mature chars (mean ± standard deviation, range in brackets) was 338.90 ± 12.64 (304.0–380.0) mm, the body weight — 437.40 ± 57.74 (235.0–735.0) g, their sex ratio was close to 1 : 1. The length of juvenile chars was 150.50 ± 9.14 (104.0–195.0) mm, the weight — 33.90 ± 6.19 (10.1–68.8) g. Blood was sampled from the caudal vessel of alive fish immediately after catching, the blood smears were dried and fixed with May-Grunwald dye and then stained with azure-eosin. Composition of leukocytes and erythrocytes was determined on the stained blood smears. The blood cells were classified according to Ivanova (1983) and Zhiteneva et al. (1989). Statistical significance of the blood cells composition differences between fish groups was assessed using the Mann-Whitney U-test, after checking for normal distribution of characteristics (Kolmogorov-Smirnov test). The erythroid row of S. malma was represented by proliferating (erythroblasts, basophilic and polychromatophilic normoblasts), maturing (oxyphilic normoblasts) and mature erythrocytes, the leukocyte row — by blast cells, agranulocytes and granulocytes. The juveniles were characterized by intense proliferative processes (great number of immature erythrocytes, large and medium lymphocytes, presence of blast cells) and appearance of poikilocytes; the sexually mature chars were distinguished by greater number of granulocytes, mainly due to stab and segmented neutrophils (p < 0.01). Parasitological analysis showed different infestation of the juvenile and adult chars by pathogenic helminths (Anisakis simplex, Eubothrium salvelini, Neoechinorhynchus salmonis) that influenced on their blood. Broad adaptive capabilities of S. malma hematopoiesis provided by wide morphological and functional diversity of blood cells are concluded that maintains homeostasis of the species. Blood indices for char from the Raduga River can be used to form reference intervals for monitoring physiological state of this species.

New data on captures of mirror dory Zenopsis nebulosa and bluefin tuna Thunnus orientalis in the coastal waters of Primorye (Peter the Great Bay and northward from Povorotny Cape) are presented.

Methods of machine learning were applied for forecasting of chub mackerel fishing grounds in the South Kuril fishery district. The problem of perspective fishing area definition was reduced for a binary classification task, i.e. the sets of environmental conditions corresponded with presence or absence of fishing operations were determined for each point within the district. The fishery statistics for 2016–2020 and the data on SST with delay of 4–7 days from the date of catch, spatial SST gradients calculated using Belkin algorithm, and day-to-day SST variations were processed using LightGBM machine learning algorithm. The model was trained on the data for 2016–2019 and verified on the data for 2020. The AUC (as an aggregate measure of performance across all possible classification thresholds) varied from 0.65 to 0.92. In the fishery season of 2020, AUC was 0.69, on average, growing to 0.75 in the period of the highest catches. Approximately 75 % of the annual catch of chub mackerel was caught at the predicted sites in 2020; this portion reached 84 % in the period of the highest catches.

Distribution and biological parameters are considered for eggs and adults of two flatfish species on the data of annual surveys conducted on the shelf of southeastern Kamchatka in summer of 2011–2014 and 2016–2019. The eggs of Pleuronectes quadrituberculatus were sampled mostly at the stage of a germinal strip forming, whereas the eggs of Hippoglossoides elassodon were mostly at the stage of embryo cleavage. The main congestions of the eggs were found in the Kronotsky Bay and northern Avachinsky Bay. The adults of both species concentrated mainly in the northern Kronotsky Bay, at Cape Povorotny. Old age groups prevailed in aggregations of P. quadrituberculatus, but middle-age and young fish — in the aggregations of H. elassodon.

Zooplankton was sampled from the epipelagic layer (0–200 m) in the Bering Sea using Jedae net (mouth 0.1 m², mesh size 0.168 mm) in 1986–2018. Arrowworms were the most numerous predators, represented with 3 species: Parasagitta elegans, Eukrohnia hamata, and Pseudosagitta maxima. Their summary biomass was 215.7 mg/m³, on average (26.3 % of the total zooplankton biomass), and varied seasonally from 105.9 mg/m³ in winter to 311.8 mg/m³ in autumn. Parasagitta elegans dominated absolutely (> 99 % WW). Mean stock of this species was 64.36. 106 t; its seasonal yield was estimated as 22.1. 106 t in winter, 78.5. 106 t in spring, 191.9. 106 t in summer, and 130.3. 106 t in autumn, so its mean production was 422.8. 106 t WW per year.

Arrowworm Saggita elegans is one of the important and abundant species in zooplankton communities of the western Bering Sea. Interannual variability of their biomass is considered on the data of long-term surveys conducted in 1986–2018, the species production is determined for the Anadyr-Navarin region and deep-water basin in 2008–2018, and the total production of zooplankton communities is calculated for 2008, 2015, and 2018. In the modern period, the biomass of S. elegans has significantly decreased compared to 1990–2000s, with exception of the shallow areas where it is relatively stable. The last decade included two periods with different oceanographic regime: the cold years (2007–2013) and the warm ones (2014–2018), but S. elegans did not demonstrate rapid response to such change of abiotic factors. However, the water circulation patterns in the upper layer were important for them and determined their transport and accumulation. For example, the high abundance and production of arrowworms in the deep-water area in 2008 and in the Anadyr-Navarin region in 2011 were conditioned by their transport and accumulation in these areas. S. elegans are predators, preying mainly upon copepods, so their impact on structure and production of zooplankton community is determined by significant grazing estimated at 50–100 % of Copepoda production or even more. The total production of zooplankton communities was higher in «warm» 2015 and 2018 than in «cold» 2008. The arrowworm production decreased in these warm years but production of non-predatory species (basically small- and medium-sized copepods) increased sharply because of their rapid response to temperature changes realized in high growth rate under higher temperature. Thus, the role of S. elegans in formation of the community production becomes lower in conditions favorable for high growth rate of non-predatory species.

Concentrations of hydrocarbons, phenols, DDT and its metabolites, Cu, Pb, Fe, Ni, DDD/DDE and DDD+DDE/DDT ratios, and total level of chemical contamination (TPF index) in the bottom sediments are traced for 16 stations in the coastal areas at Vladivostok in 1982−2017. Temporal variations of the concentrations and derived indices are classified to 4 types of dynamics, using the methods of exploratory and confirmatory factor analysis, crosscorrelation analysis, and fuzzy set classification procedure. They are: primary contamination; secondary contamination; exponential growth; and polymodal dynamics. These variations are induced by two main sources of pollution, such as the industrial influx including wastes from Vladivostok and nearby settlements, aeolian transfer and polluted precipitations, and the terrigenous influx with polluted freshwater discharge. Impact of the first source prevails in the Golden Horn Bay, Diomid Inlet and Eastern Bosphorus Strait, and the second source is important for the Amur and Ussuri Bays (the coast of Vladivostok in these bays is influenced by both sources with predominance of the second). The terrigenous impact has two modes depended on certain processes of contamination: the permanent pollution inherent in the types of secondary contamination and exponential growth and the extreme pollution that forms the polymodal dynamics. The secondary contamination follows the primary one with a lag of 6–7 years. The secondary contamination of terrigenous usually has inverse correlation with the Razdolnaya/Suifen River discharge; for instance, strengthening of the freshwater inflow causes lower concentrations of Cu and Pb in the bottom sediments due to dilution effect. On the contrary, contamination depends directly on the Razdolnaya/Suifen River discharge for the exponential growth of terrigenous — the stronger the freshwater inflow, the higher the concentrations of Fe, Ni, and phenols (the latter is a sign of eutrophication). The types of dynamics change following the balance between pollution and self-cleaning of the sediments that is determined by external factors, as a drop in economic activity and its subsequent recovery, limitation and finally ban for using of tetraethyl lead additive, extreme floods on rivers, etc.

Time series of air temperature and sea surface temperature in South Kuril region in July and August are extrapolated to 2020–2024 using modified method of Fourier decomposition. Both cyclic harmonic components and linear trend are accounted. Two main cycles with period of 2 years and 6–7 years dominate in variability of air temperature anomaly (in Wakkanai, Abashiri, Nemuro) and sea surface temperature anomaly (at Кurilsk, Yuzhno-Kurilsk, Malokurilskoe, in the area of Soya Current, and in the area southeastward from Hokkaido), as well as in variability of AT 500 hPa height in the regional centers of atmospheric action, as Far-Eastern depression and Okhotsk anticyclone.

Patterns of atmosphere baric fields preceeded to development of extreme thermal modes in the South-Kuril area in summer are identified using the interval approach to their recogni tion. The best recognition rates are noted for the field of AT 500 hPa over the region of East Asia in February, March, May, and June. Extreme cold summer conditions in the South-Kuril area in summer were preceeded by development of AT 500 hPa trough and baric depression at the sea surface over East Asia in these winter and spring months. Warm summer conditions in the South-Kuril area were preceeded by opposite patterns, as AT 500 hPa ridge over the North-West Pacific and high pressure over the Okhotsk Sea, with positive anomalies of H500 height over the North-West Pacific and Kuril Islands.

Mixed herds of pink salmon including the fish of both artificial and natural origin are exploited by fishery in many areas of Sakhalin Island. To separate the fish of different origin, large-scale tagging of the juveniles otoliths is conducted at salmon hatcheries since 2008. The hatcheries contribution to pink salmon catches in certain areas of East Sakhalin (from the Langeri River to Cape Crillon) is assessed for 2011–2017 on the base of previously published and new data on occurrence of the fish with marked otoliths. The specimens were sampled from commercial catches of 5–13 fixed nets and from research catches in 5–9 rivers throughout entire spawning season. In total, 40,992 otoliths of pink salmon were collected. The otoliths were prepared for microstructure analysis using standard methods of processing. All marked otoliths had the tags of hatcheries located on the eastern coast of Sakhalin. The fish of artificial origin were caught in all examined sites between Cape Soymonov and Cape Crillon every year, but in some years their distribution was wider, up to the northern limit of the investigated area (Langeri River). The fish of artificial origin migrated to all rivers within this area. The total annual landing of the pink salmon marked at artificial hatcheries in the East Sakhalin waters was estimated as 300–10600 t, by years. The rest of the fish of artificial origin (0.4–2.3 . 106 ind.) entered to the rivers and mostly reached the spawning grounds. Long-term dynamics of landing was compared for the pink salmon of artificial and natural origin and their independence was concluded. Distribution of pink salmon originated from certain artificial hatcheries by sites of catch was rather constant that allowed to extrapolate the results for marked fish to all released pink salmon. The highest contribution of pink salmon of artificial origin was noted for catches in the Aniva Bay (23.9 %, on average), it was lower for catches at the southeastern coast of Sakhalin (13.2 %), and more lower for catches in the Patience Bay (7.6 %). Total number of pink adults of artificial origin caught on a particular stretch of coast did not depend directly on the number of pink juveniles released from a local hatchery, but was determined mainly by number of fish migrated there from other hatcheries. The landing of pink salmon originated from artificial hatcheries directly in the rivers where these hatcheries were located and at their mouths was < 10 % of the total catch of pink salmon of artificial origin. Schemes of quantitative distribution of pink salmon with marked otoliths in the waters of East Sakhalin are presented.

Some components of alcohol extracts from seagrass of genus Zostera were fractioned in the column filled with sorbent Sephadex LH-20 using the methods of size exclusion chromatography. Content of polyphenols in the fractions and their antioxidant activity were determined. The total content of polyphenols in the extracts from Zostera asiatica collected in the Rudnaya Bay (Japan Sea) and Zostera marina from the Aniva Bay (Okhotsk Sea) was 2.10 and 2.15 mg/mL, or 0.4 and 1.8 mg/g DW, respectively. The antioxidant activity varied by fractions in the range 19.1–118.0 μg of ascorbic acid per mL for Z. asiatica and 96.2–213.9 μg of ascorbic acid per mL for Z. marina, in dependence on qualitative and quantitative composition of the fractions. The alcohol extracts of Zostera were heterogeneous systems with different polyphenol components and included protein substances covalently bound with polysaccharides and/or polyphenols, that was confirmed by UV spectrometry and thin-layer chromatography. Phenolic acids, flavones and flavonols were presented in the extracts.

Chemical composition and nutritional and biological value of roe are investigated for autumn chum salmon from the Amur River sampled during their run for spawning from the estuary to the area of Khabarovsk city. Color and strength of roe were examined, content of proteins, lipids and minerals was measured, amino acid and fatty acid composition was determined. Caloric capacity and biological value of the samples were usual for this species. Physical properties of the roe (strength, color intensity) practically did not change in dependence on distance from the river mouth. Stable quality of roe in the run of spawning migration in the lower Amur is concluded.