All available data on sakhalin sturgeon Acipenser mikadoi are summarized. Its historical and modern habitats are described and their significant reduction is noted. Now the species is abundant in the Russian part of its range only — in the Tumnin River, where it is represented in commercial catches by two clearly different groups: large-sized juveniles (FL 43–68 cm) and mature fish (FL 135–169 cm). Juveniles of sakhalin sturgeon migrate during their first years, as their osmoregulatory system forms, to the lower reaches of Tumnin, to the internal estuary, and then to the Datta Bay, the Tatar Strait and the Japan Sea. When returned to the Tumnin, the spawners of sakhalin sturgeon have the length 135–169 cm (n = 29) and weight 15–36 kg. Sex ratio among the caught mature fish is 13.0 : 4 or 3.2 : 1 for females : males, on average. Fecundity of the sturgeon females sampled for artificial reproduction varied from 44.8 to 150.0 thousand eggs, on average 87.3 ± 12.1 . 103 eggs. In total, 17 mature spawners of A.mikadoi were caught in the Tumnin River in 2006–2019 for artificial reproduction (♀ = 13, ♂ = 4), 13 individuals were injected, among them 4/5 of females and 2/3 of males gave high-quality sex products. Producers of this species were distinguished by high survival during manipulations of fish breeding (100 %). Their progeny had low survival, both embryos during incubation and juveniles during rearing; the survival rate for the stage from eggs laid for incubation to juveniles with weight 3.4–7.0 g was 1.85 %. The low survival was supposedly reasoned by combination of unfavorable environmental factors and fish-breeding manipulations. Totally 11,214 juveniles of sakhalin sturgeon with weight from 3.4 to 7.0 g were released into the natural habitat (Tumnin river) in 2007, 2008, 2015, 2017, and 2019. At Anyui sturgeon fish hatchery, the broodstock of sakhalin sturgeon with 274 individuals of 5 ages is created and operated successfully. The male sturgeons in the hatchery mature at the age of 8 years. Here, 11 males of the 2007–2008 year-classes participated in the spawning in 2015–2019. Re-maturation of males was not recorded yet. For the broodstock formation in other fish hatcheries, 200 juveniles of sakhalin sturgeon were transferred to them. To preserve the species, a set of measures is proposed to strengthen its protection and to enhance its artificial reproduction, including the fry releasing into the rivers of the mainland coast, Sakhalin Island, and Japan.

Iturup Island (in southern Kuril Islands) and southeastern Sakhalin Island are known by the highest catches of salmons within the Sakhalin-Kuril region. The timing of pink salmon mass return to Iturup is 5–10 days later than to Sakhalin, and the females returned to Iturup have higher relative individual fecundity, on average. In 2014, an unexpected increase of pink salmon catches occurred on southeastern Sakhalin Island, with a simultaneous sharp decrease of the catches on Iturup Island. Assumption on appearance of Kuril pink salmon in the Sakhalin waters was confirmed by analysis of the scale parameters (number of sclerites and intercirculi distance in the first-year scale zone), dynamics of catches, and individual fecundity of females. Sharp opposite changes of the pink salmon catch dynamics were noted again for these areas in 2017 and 2018. Such changes of pink salmon abundance could be reasoned by environmental conditions of reproduction in these areas or new redistribution between two areas. To clarify the issue, complex analysis (same as for 2014) was applied for pink salmon at southeastern Sakhalin and Iturup in 2017 and 2018 (187 and 215 fish samples from Sakhalin and 194 and 152 fish samples from Iturup in these two years, respectively). The results were interpreted following the hypothesis of fluctuating stocks. Taking into account the complex of traits, there is concluded that the assumption about redistribution of pink salmon between southeastern Sakhalin and Iturup Island in 2017 and 2018 is untenable.

Catch of walleye pollock by Russia is the highest in the northern Okhotsk Sea where on average 0.94 million metric tons were caught annually in the period between 1962 and 2017, or around 24 % of the total yield of Russian fishery. The total stock and spawning stock of pollock grow there since 2002, though the catch per unit effort (CPUE) has significantly decreased in the beginning of 2018 despite expected high levels of both total and spawning stocks. The sea surface temperature, ice cover and storms frequency were examined as possible reasons of low fishing efficiency in 2018. For this purpose, the generalized linear models (GLM) and generalized additive models (GAM) of catch dynamics are compared. GAM with addition of temperature and storms factors has the lowest Schwarz’s Bayesian criterion and the highest explained deviance (61.6 %). Efficiency of fishing gears has nonlinear relationship with the towing time. CPUE has hypersensitivity to the stock biomass presented as the power dependence (γ = 0.94, r = 0.923). Standardized CPUE is recommended for using in the final GAM for the pollock stock assessment in the northern Okhotsk Sea, hypersensitivity of CPUE should be estimated and corrected if necessary.

Fishery at the northwestern Okhotsk Sea coast is analyzed for the period from 2000 to 2019. Pacific herring, saffron cod, pacific cod, capelin, flounders (Limanda aspera, Pleuronectes quadrituberculatus and Platichthys stellatus), and smelts (Hypomesus japonicus and Osmerus mordax) are landed in this area. The spawning herring prevails (95.2 %) in the catch. Almost all spawning herring is caught at the coast of Khabarovsky Krai. Taking into account the area of spawning grounds for herring in the lagoons of the coasta, withdrawal of this species could be increased, though actually it was decreased in the last two decades in 1.8 times, and since 2012 the herring fishery is continued in Okhotsk District only. The fishing strategy changed: offshore harvesting with stationary nets transformed to combined using of stationary and casting nets and expanded to the rivers. The catches delivery changed, as well: the herring catches are processed mostly ashore since 2008. Withdrawal of saffron cod fluctuated from 1.9 % to 186.5 % of the total available catch (TAC) volume for this species, with rapid growth in the last 5 years; its main fishing grounds shifted from the waters of Nikolayevsk District to the waters of Tugur-Chumikan District. Landings of smelt grew since 2009, too: annual catches of rainbow smelt increased from 72.2 t, on average, in 2009–2014 to 119.4 t in the last 5 years (up to 90 % of this volume was caught in Tugur-Chumikan District); landing of japanese smelt grows even faster and now exceeds 50 % of TAC. The stock of capelin was exploited weakly, annual catches of this species changed from 0.7 % to 23.3 % of TAC. Stationary and casting nets were the only fishing gears used for the capelin fishery in 2000s, but recently midwater trawls are also used. Catches of flounders had a growth tendency, though they were rather low and never exceeded 50 % of the recommended volumes. Dynamics of the pacific cod landings became positive when fishermen started to use small boats for this fishery, its annual catches increased in 2014–2019 from 69.7 to 84.8 t, the withdrawal rate achieved 9.3 % of TAC. Available fish resources in the northwestern Okhotsk Sea and technical equipment of local enterprises provide strong potential of fishery industry in this area.

In the Amur River, there are two ecological forms of pond smelt Hypomesus olidus: anadromous and freshwater. Generalized information about biology and fishery of the anadromous form of pond smelt is presented. The smelt migrate to the Amur for spawning in winter and spring, and for wintering in autumn. The most remote point of their spawning migration is Bolbinsky cliff (375 km from the mouth). The spawning herd is represented by three age groups: 2-, 3-, and 4-year-old fish; the two-year-old fish are the most numerous. The sex ratio of spawning smelt is close to 1 : 1, though females prevail slightly. Body length of the pubescent fish ranges from year to year from 7.6 to 13.2 cm, body weight — from 3.05 to 16.04 g; females are slightly larger than males. Absolute fecundity of pond smelt ranges from 0.7 to 12.4 thousand eggs, relative fecundity — from 199 to 1287 eggs/g. During migration to the spawning grounds, the smelt practically do not feed, but they go to active feeding after spawning. Pond smelt is a popular object of fishery in the Amur basin: on average 1569.2 t were caught annually in 2010–2019, during the spawning migration, mainly in the lower Amur River between Nikolayevsk-on-Amur and Bogorodskoe.

Data on age structure, shell size (height, length, thickness) and weight of oyster Crassostrea gigas in the Losos Bight (Aniva Bay, Okhotsk Sea) are presented on results of the surveys conducted in 2018 and 2019. The size-age key for the total weight is plotted. The size-age structure is compared with oysters from other habitats.

Fecundity and some other reproductive characteristics of tanner crab Chionoecetes bairdi females are studied for the first time in the area at southeastern Kamchatka on the materials collected in spring and summer aboard research vessels (in 2016 and 2019) and fishing boats (in 2020). The females with new eggs prevailed in the catches. The size of functional sexual maturity was determined as 79 mm. The implemented fertility was estimated as 93.4 ± 28.1.10³ eggs in 2016 and 115.7 ± 24.5.10³ eggs in 2019, on average. Reproductive effort and K/r-coefficient were evaluated; their relatively high values confirmed r-strategy of tanner crab reproduction.

Light dusky rockfish Sebastes variabilis is a rare fish species in the waters at East Kamchatka, rarely recorded in trawl catches. They aggregate in the areas with complicated bottom topography and active water dynamics with the depth from 118 to 316 m. Their maximum catches are recorded off Capes Gowen, Olyutorsky, and Kronotsky. The light dusky rockfish body length varies from 34 to 50 cm, and body weight — from 0.53 to 1.78 kg. Some issues related to the migration routes of this species to the shores of Kamchatka are discussed.

Size and sex structure of the mysid Paracanthomysis shikhotaniensis aggregations in Peter the Great Bay (Japan Sea) is considered. The samples were collected at the depth of 0.5–2.0 m at Reineke Island in May-October of 2014–2018. All sampled mysids (1601 ind.) were measured under binocular microscope with accuracy of 0.1 mm, weighted by torsion scales with accuracy of 1 mg, and separated to males, females and juveniles. The females were differentiated by 5 stages of their development: 1) immature females with oostegetic rudiments; 2) oviparous females; 3) females with embryos in the marsupia bags without stalk-eyes with black pigment; 4) females with embryos in marsupia bags with black eyes; and 5) spawned females with empty marsupii. Their body length varied from 5.0 to 27.8 mm, being much larger in spring and early summer than in late summer and autumn. Juveniles were absent in spring, but abundant in July-October. Females were larger than males, their body length varied from 9.0 to 27.8 mm, whereas the length of males — from 8.3 to 19.0 mm. Seasonal variations of the size structure were similar in different years, with small deflections due to changes of water temperature and weather conditions. In contrast, sex structure of the mysid aggregations had significant interannual differences. The females to males ratio was almost stable from June to September (females prevailed), but changed to males domination in October. Spawning of P. shikhotaniensis was extended in time because of several generations spawned, that was confirmed by permanent occurrence of females with embryos at different stages of development.

Size and sex structure of estuarine-freshwater mysid Neomysis awatschensis in the northern Amur Bay is considered, time of their aggregations formation is determined, and their biomass is estimated on the data of surveys conducted in 2014–2019. The samples were collected at the depth of 0.5–2.0 m in the daytime in May-July. The catches were recalculated per 1 m³ of water. All collected mysids (2212 ind.) were measured under binocular microscope with accuracy of 0.1 mm, weighted by torsion scales with accuracy of 1 mg, and separated to males, females and juveniles. The females were differentiated by 5 stages of their development: 1) immature females with oostegetic rudiments; 2) oviparous females; 3) females with embryos in the marsupia bags without stalk-eyes with black pigment; 4) females with embryos in marsupia bags with black eyes; 5) spawned females with empty marsupii. Time and duration of N. awatschensis aggregating changed by years in dependence on hydrological and weather conditions; the aggregations were either monospecific or mixed with another mysid species — N. mirabilis. The maximum mysid biomass could exceed 500 g/m³ that was appropriate for commercial fishery. The maximum body length of mysid females was 13.7 mm, of males — 12.0 mm. The average length varied from 6.7 to 10.3 mm, being shorter in summer months than in May. Portion of males in the aggregations was always significant (16.3–50.7 %), portion of females varied from 8.7 to 52.5 %, portion of juveniles was the largest in June (29.9–75.0 %). The females to males ratio was 1 : 1 in May and July of 2014–2017, but males prevailed in June 2015 (1.0 : 1.9), whereas females prevailed in June 2016 (1.8 : 1.0). Spawning of the mysids was the most intensive in May-June, though females had embryos at different stages of development in all samples that indicated an extended period of reproduction.

Interannual variation of the water level in Lake Khanka is considered on satellite altimetry data; its extreme rising in recent years is noted, with the maximum in 2016. Using a simple balance model, contribution of the main components of its water balance to the modern rise is determined, as precipitation in its basin, evaporation, and water discharge through the Sungacha River. Growth of summer precipitation is defined as the main reason of the level rising. However, the water income to the lake does not correlate with the precipitation volume since 2010 that confirms the hypothesis about artificial influence on the water balance of Lake Khanka by its connection with the Mulin River (China) and worsening of the outflow through the Sungacha. As the result, the lake got additionally about 1.3 km³ in 2014–2015 that promoted the level rise to the highest mark. But before and after this period, the water inflow was lower than its expected values, obviously because of its redistribution. Positive influence of the anomalous water level growth on total abundance of commercial fish species is shown. The high level is favorable for reproduction of phytophilic species (Cyprinus rubrofuscus), whereas abundance of pelagophilic species (Chanodichthys erythropterus) declines.

Satellite data on the sea level heights and data of Argo floats for the southwestern Bering Sea and adjacent area of the North Pacific are analyzed. Interannual variability of the thermohaline structure and water dynamics caused by the nodal (declination) tide with the period of 18.6 years is revealed. The tidal-induced 18.6-year variability is traced in variations of the sea level, water temperature and direction and velocity of the geostrophic currents. Extreme strengthening (in 2006) and weakening (in 1997 and 2015) of nodal tides led to lowering/rising of the sea level heights in the southwestern Bering Sea and in the areas southward from the Near Strait and Commander Islands. The sea level lowering was associated with increasing of salinity and water density in the layer of 50–400 m; as the result, the salinity and density at the depth of temperature minimum (~100 m) were higher in 2005–2006 than in 2015–2016 by 0.20 psu and 0.14 kg . m–3, respectively. This increasing can be explained by transformation of the Alaskan Stream waters due to intensified tidal mixing in the Aleutian Passes and in the Near Strait. No statistically significant correlation between the sea level and amplitude of the nodal tide was found in the areas remoted from the straits. Another consequence of the sea level lowering was an appearance of cyclonic circulation northward and southward from the Near Strait and weakening of the Alaskan Stream in spring of 2006, with cessation of the flow from the Near Strait to the mainland coast that caused SST decreasing in the southwestern Bering Sea. Intensification (weakening) of nodal tides was accompanied by decreasing (increasing) of sockeye salmon catches at East Kamchatka and Aleutian Islands.

For the first time, generalized data on parasites of two subspecies of arctic grayling (Thymallus arcticus pallasi and Th. a. mertensi) from the largest salmon rivers of the northern coast of the Okhotsk Sea, as the Taui, Yama and Gizhiga, are presented. In total, 39 species of parasites are found including 38 helminth species belonging to 26 genera, 19 families, 5 classes and 3 types (Plathelminthes, Nemathelminthes, and Acanthocephales), and 1 parasitic copepod (Crustacea; Arthropoda). Among the flatworms, trematodes have the highest species diversity — 19 species belonged to 8 genera of 6 families, and cestodes are presented by 6 species (6 genera of 5 families). Nematodes are presented by 8 species (8 genera of 5 families), and acanthocephalans — by 5 species (4 genera, 3 families, 2 classes). The graylings parasites are distributed with 2 ecological groups: the freshwater parasites including 29 species (4 cestodes, 16 trematodes, 5 nematodes, 3 acanthocephalans, and 1 copepod) and the marine parasites including 10 species (2 cestodes, 3 trematodes, 3 nematodes, and 2 acanthocephalans). Th. a. mertensi from the Taui River basin is distinguished by the highest diversity of parasites (32 species), their high diversity is observed for the same species from the Gizhiga (20 species), and for Th. a. pallasi from the Yama (24 species), as well. More than a half of helminths (22 species) are noted by medical and veterinary importance and/or are able to spoil organoleptic properties of the seafood.

Seasonal and long-term variability of the ice age and concentration in the Japan Sea is analyzed on the base of all available information for 1960–2019. The highest variability of ice concentration is localized in the area with concentration 7–8 points (70–80 %) and follows to shifts of this area: form north to south in early winter and back to the north in late winter. The highest variability of ice age is associated with the area of young ice (age 1–3 points), where influence of melting or freezing on the ice thickness is the greatest. The areas of in-phase and out-phase variability of the ice age and concentration are identified and compared by analysis of standard deviations and 3 the first eigenvectors for restored mid-month fields of ice cover in December-May. Contributions of 3 the first empirical orthogonal functions (EOF) to total variability of the ice cover are determined. Cyclics with periods of 9–12, 2–4, and sometimes 15–16 and 4–6 years are found in variation of EOFs for the ice age and concentration; besides, the 5–7 years periodicity occurs in the ice age spectra for December, January and April.

In the rough sea, the ridge of linear hydrobiotechnical structure (HBTS) presumably takes a shape of catenary line under the buoys lifting force evenly distributed along its length, with the maximum deflection equal to the wave height. Using the catenary line equation, length of the chord is calculated for typical cases of the sea roughness of 4, 5 and 6 points (wave height of 2.0 m, 3.5 and 6.0 m, respectively) and shifts of the end buoys, angles of inclination and tensions of the anchor guy are determined for these cases that allows to estimate magnitude of the anchor shear force, at which the anchor begins to slide. On the basis of these estimations, a mushroom-shaped anchor is recommended to use, which holding force exceeds the shear force.

Fucoxanthin is a widespread carotenoid contained in tissues of brown algae, known by its antitumor activity and ability to suppress cancer cells growth. Its inclusion into diet prevents accumulation of the body fat and regulates level of glucose and insulin in the blood. Fucoxanthin can be considered as a promising nutritional supplement for suppressing obesity. Extraction of fucoxanthin from brown algae Sargassum pallidum is investigated under various conditions. The samples of algae were collected in different sites at Primorye coast in 2018–2019. Two types of the preparations were used ― frozen and dried. The frozen preparations were stored under temperature of –18 оC no more than 30 days. For the dried preparations, fresh algae were dried in a dark room by air fan under temperature of +18–+20 оC and then crushed to powder and stored in dark place under the same temperature no more than 6 months. Content of dry substance in the preparations was 16.4 ± 1.0 % for frozen algae and 93.6 ± 1.0 % for dried algae. Fucoxanthin was extracted from these preparations by method of alcohol extraction using the ethanol water solution in ratio of 1 : 10 during 24 hours in a dark place, then the solution was filtered or centrifuged. Concentration of fucoxanthin in the filtered solution was measured in spectrophotometer relative to a standard solution (ethanol 96 %) with wavelength of 350–800 nm. Yield of fucoxanthin was higher from the frozen preparations, but more ethanol was consumed for its extraction in comparison with extraction from the dried preparations. Besides, the dried preparations were processed during 1 day with the ethanol solution in concentration 96, 88, 84, 80, and 76 %, under various temperature. Yield of fucoxanthin decreased with temperature increasing: the optimal temperature was +7 оC, so the room temperature could not be recommended for extraction. The optimum concentration of ethanol for fucoxanthin extraction was 80 ± 2%.

Spatial distribution of stations made by research expeditions of TINRO in the Okhotsk Sea in 1984–2019 (82 surveys) is considered. The schemes of stations are sorted by decades, years, seasons, and months. Information the number of daylight and nighttime stations and the stations distribution by time of day, years, seasons, and by 33 biostatistical areas is presented in table form, that allows to estimate the data coverage at regional and temporal levels.

Spatial distribution of stations made in research expeditions conducted by Pacific Res. Inst. of Fisheries and Oceanography (TINRO) in the Bering and Chukchi Seas and in the North Pacific in 1986–2019 is discussed. Schemes of the stations for every cruise are presented and sorted by decades, years, seasons, and months. The data sufficiency is estimated at regional and temporal levels by calculation of the stations number in the daytime and nighttime, per years, per seasons, and per biostatistical areas.