On materials of the diving survey conducted in 2010, using additional data obtained from 1999 to 2023, sublittoral vegetation at the northwestern coast of the Japan Sea is described. Basing on the concept of adaptive zone, 16 associations are identified (Ulvetum fenestratae, Saccharinetum japonicae, S. cichorioidae, Kjellmanielletum crassifoliae, Costarietum costariae, Agaretum clathratae, Desmarestetum viridae, Sargassetum miyabeae, S. pallidae, Stephanocystetum crassipae, Bossielletum compressae, Ptilotetum asplenioidae, Odonthalietum corymbiferae, Zosteretum marinae, Z. asiaticae, Phyllospadicetum iwatensis) and a group of communities of encrusting calcareous algae. These associations are not abstract classification units, but mosaics of homogeneous adaptive zones of their main dominants considered as elementary Petersen-type communities where on average 58 % of bottom cover and 53 % of biomass are formed by the main dominant species. The associations of the upper layer can be identified visually, with assessing the projective coverage of main dominants and subdominants for each of them using underwater drones. Visual identifying for subordinate species is less available, as well as quantitative assessment of their coverage. The total area occupied by the vegetation associations is 217 km2 , i.e. about 2/3 of the total vegetation belt. The total biomass of vegetation within the associations is estimated as 1248 . 103 t, of which the biomass of the main dominants is 709 . 103 t. Commercial and potentially commercial resources of macrophytes are generally confined to their associations, that allows to estimate the total stock in 324 . 103 t, including 94 . 103 t of the only commercially used species Saccharina japonica. These stock values have no statistically significant difference from earlier estimations (p = 0.79), that approves using the concept of adaptive zone for assessment of commercial resources of subtidal vegetation.

To compare trophic properties in pelagic and benthic communities of the Kara Sea, isotopic composition of carbon and nitrogen (δ¹³C and δ¹⁵N) was examined in tissues of zooplankton, zoobenthos, and fish. The organisms exhibited rather low δ¹³C values in the surveyed area. Because of stable difference in isotopic composition of carbon for zooplankton and zoobenthos, the pelagic and benthic communities could be separated by the level δ¹³C = –21.5 ‰, on average. The δ¹⁵N values for these communities varied within their 3 trophic levels in the range from 6.4 ‰ (for bivalve Serripes groenlandicus) to 16.3 ‰ (for lycod Lycodes seminudus), reflecting the input of predation. The bottom and pelagic communities in the Kara Sea demonstrated trophic interdependence. Both pelagic and bottom fish species, more or less, consumed both pelagic and benthic prey. Taking into account the content of ¹³C isotope in tissues of zooplankton and zoobenthos, about 40 % of the bottom nekton species were linked mainly with the pelagic food web and bypassed the benthic one. Pelagic fish fed mainly on pelagic prey, though the portion of zoobenthos in food of the dominant species — arctic cod had increased with the fish size increasing. On the contrary, the portion of zoobenthos in food of ruffed flounder had decreases with their size.

Reasons for deviations in actual number of sexually mature offspring from the parent-offspring ratio described by Ricker equation are investigated for coho salmon in the Okhotsk district. The deviations are well explained by variability of air temperature and precipitation during the feeding period of juveniles in rivers. Combined influence of the number of parents and weather conditions in the freshwater period of life explains more than 90 % of variability for coho salmon year-class strength. The influence of weather factors is realized possibly through conditions of nutrition and growth of juveniles. The results are discussed in comparison with similar studies of some populations of pink and chum salmon.

State of stocks and fishery and some general features of biology are considered for saffron cod in the Bering Sea on results of bottom trawl surveys and commercial fishery statistics in 2000–2023. In 2023, the stock in the southwestern part of the sea is estimated in 114 . 103 t, in the northwestern part — in 20 . 103 t, and at the coast of Chukotka Peninsula — in 0.14 . 103 t. The average annual catch of saffron cod in the southwestern and northwestern parts of Bering Sea is amounted in 8.5 . 103 t and 1.1 . 103 t, respectively. The saffron cod fishery at Chukotka is absent.

Large-sized specimens of a new for the Caspian Sea mollusk were found in spring 2023 in trawl catches of the survey conducted by the Volga-Caspian branch (CaspNIRKH) of the Russian Res. Inst. of Fisheries and Oceanography. Using molecular genetics research methods, including sequencing of the cytochrome oxidase gene of mitochondrial DNA, the species is identified as Mytilus galloprovincialis — the Black Sea mussel. In summer, the invaders were recorded in bottom samples in several areas of the sea. Features of the species biology allow its naturalization into the Caspian Sea ecosystem that will contribute to enrichment of the food base for fish and involve this filter-feeding mollusk to the processes of self-purification of the sea.

Total content of phenols in seawater and bottom sediments of some water areas in Peter the Great Bay in 1998–2022 is considered. Mean annual values of phenol concentration exceeded the maximum allowable level for the water of fishing grounds but were comparable with the background concentrations in water and bottom sediments. Peaks of phenol concentration were usually observed in the estuaries of rivers, so the rivers are considered as the main source of phenol pollution: the Razdolnaya in the Amur Bay, the Shkotovka and Artemovka in the Ussuri Bay, and the Obyasnenie in the Zolotoy Rog Bay. Other significant sources of pollution were the urban wastewater discharged to the eastern Amur Bay and wastes of shipbuilding and ship repair plants and marine vessels. Downward trend of the total phenol content was revealed for all water areas, but pollution of bottom sediments by phenols was still high in the Ussuri Bay in 2019–2022.

Conditions of salmon reproduction in 2016–2020 are considered for seven Sakhalin fish hatcheries: Lesnoy, Taranaysky, Buyuklovsky, Firsovka, Lazovoy, Lublino, Okhotsky, with evaluation of water temperature, dissolved oxygen content, and qualitative and quantitative parameters of sanitary-indicative and conditionally pathogenic microflora in the water entered the hatcheries at the stages of eggs and larvae incubation and rearing of juveniles. Indirect indicators as morbidity and mortality of fish were used for the conditions assessment, as well. At all examined hatcheries, the water met requirements for water bodies suitable for fisheries by microbiological indicators. The water temperature and dissolved oxygen content provided rather favorable conditions for the salmon reproduction at all stages of the breeding cycle that was proven by normative values of fish mortality and absence of diseases. However, ranges of temperature and oxygen content at certain stages of chum and pink salmon breeding were wider than the optimal ones described in technological documents and scientific literature.

Results on experimental cultivation of seedlings of laminaria kelp Saccharina japonica are considered. Growing of this species was conducted in the first time in the Center of Mariculture located on Popov Island in the coastal Japan Sea. Data on equipment of the modules for cultivation of early stages of algae and on environmental conditions for their optimal growth are presented. Diatoms influence on the growth of kelp seedlings is shown. The optimal dates for seeding the spores on artificial substrate frames and for the frames transplantation into the sea are determined that provides the most rational growing cycle in a forced mode.

Results of red-clawed crayfish cultivation in pond aquaculture in the Astrakhan Region are presented. Growing of Australian red-claw crayfish Cherax quadricarinatus juveniles in ponds with different distribution density and periods of cultivation within the summer-autumn seasons are analyzed and basic requirements for the pond cultivation of this species are determined. The optimal dimensions of pond are the following: area 0.1–0.5 hectares, depth 1.5–2.0 m, V-shaped bottom. Ponds with natural fodder base should be prepared in 20–30 days before placing the crayfish. Artificial fertilization is available for ponds with depleted soil by 3–5 t/ha of manure applied locally in the area of the pond water supply in 20–30 days before the placing. Zooplankton abundance can be increased with input of Cladocera culture, as Daphnia magna (Straus 1820), in amount of 100–500 g/ha. Coastal aquatic vegetation should not occupy more than 5 % of the pond area at the beginning of cultivation and 15 % by its end. Duration of juvenile crayfish growing in ponds of the Astrakhan Region is limited by temperature conditions (water temperature > 20 ºC is favorable for the growth) and does not exceed 115–125 days depending on the water heating. At least 100 days of growing are necessary for successful harvest. The optimal mean daily temperature of water in ponds for growing and harvesting crayfish is 23–24 ºC. Certain conditions and dates of rearing can be chosen to get certain body size of production. Small-sized juveniles with weight below 0.1 g are used for growing to the weight of 40 g in 80–100 days for the purposes of both further cultivation, replenishment of the broodstock, or sale. For producing crayfish with the weight > 40 g, juveniles with larger initial size (2–5 g) should be grown in 90–100 days. The individuals with the weight > 5 g are used as producers of planting material; at least 100 days are necessary for growth to this size. Rearing such individuals in controlled conditions (e.g. in closed water supply installations) allows to obtain the progeny in the fall of current year.

Cage aquaculture is a relatively low-cost and quite effective method of fish farming, particularly important for the Astrakhan Region in recent times. Sturgeon species are grown in the farms there mainly. The most favorable conditions for cage aquaculture are provided in flowing water of both natural and anthropogenic nature. Features of environments for cage fish farming are considered for several operating fish farms at the Khurdun River that is rather demanded for these enterprises due to accessibility to roads, proximity of settlements and so suitability for the farm servicing and selling the products. However, the river is rather impacted to anthropogenic activity, including pollutions from the fish farming itself. Standard methods of hydrology, chemistry and biology were used. The fish farms at Khurdun River were differed in their production capacity and the volume of aquaculture production, though the depth of the cage lines installation was sufficient for the fish growing everywhere. The flow velocity was rather slow and decreased at cages of the most farms relative to the background value. Dissolved oxygen content in water was quite high, but great vertical differences were observed in summer, with supersaturation at the water surface and oxygen consumption for oxidation of organics at the river bottom. The value of chemical oxygen consumption exceeded the norm both at the surface and at the bottom and increased downstream. By taxonomic composition of bioindicator benthic organisms, the studied water body was classified to categories from “clean” to “very dirty”. Some deterioration of environmental quality downstream from the cage lines was detected relative to background values. Sanitary and microbiological tests of water revealed an exceeding of the total microbial count at 22 o С relative to this one at 37 o С in all seasons, that is a sign of water self-purification worsening. Faecal pollution of the river water was found and confirmed by a presence of Enterococcus faecalis in abnormal concentration, in particular in summer-autumn low-water season. In general, environmental conditions in some sites of the Khurdun River can be considered as tense in the summer-fall season by a number of parameters. Deterioration of environmental regime in conditions of rising temperature and slowing flow in the summer-fall low-water season should be accounted for adjustment of planting density and feeding of farmed fish.

Feeding habits of salmon are examined on the data from “Trophology” and “Zooplankton” databases for 1988–2023, taking into account calendar dates and spatial localiza tion of the salmon size classes. The dominant zooplankton species and groups in salmon food are defined and their availability in terms of time and depth of habitat is determined. Daily rhythm of salmon feeding is found uniform for all size groups. The areas and time (months) of maximum concentrations of salmon are determined, by size groups, and those ones are considered as the areas and periods of their most active consumption. A trophological calendar is constructed to show where, when, and what type of food is consumed by certain species and size group of salmon. Daily food rations are calculated for all salmon species and size groups. The rations are similar with those in the Bering Sea, with small differences possibly caused by different structure of the plankton communities. The application tables are compiled for operational calculations of total food consumption by size groups of salmon species with a predominant zooplankton prey (pink, chum and sockeye). According to the forecast published at VNIRO website vniro.ru, the salmon catch in the Far Eastern basin will decrease by more than 2 times in 2024, primarily due to pink salmon. In this case, significant reduction in salmon pressure on plankton community can be expected.

Unmanned aerial counting of pacific salmon in the rivers of the Okhotsk district (Khabarovsk Region) in 2021–2023 is analyzed. Estimates of the spawning redds number and the spawners abundance are presented for the monitoring sites. Prospects for using these indices for forecasting the stocks are discussed. Specifics of unmanned counting are considered, and options for further development of the methodology are proposed. The method of unmanned counting is suitable for information support of the stock forecasts only, but can be modified for application in fishery management and spawning grounds inventory. Possibilities for further automation in the unmanned counting of pacific salmon are considered on the base of the authors’ experience and literature information. Proposed approaches to automation are outlined for key stages of unmanned counting, as spatial coverage planning, aerial photography acquisition, photogrammetric processing, vectorization, and abundance estimation. Features of the automation implementation depend on purposes of the counting and are different for the stock forecasting, fishery management, and spawning grounds inventory. Adequate automation should be based on ensuring consistency and mutual balance of approaches used at different stages of the counting.

High statistical significance of water temperature at the sea bottom T and depth D for distribution of pacific cod in the West Bering Sea fishing zone is found in several tested models tuned on the data of bottom trawl surveys conducted in the period between 1977 and 2021 not deeper than 400 m. The vector autoregressive spatio-temporal (VAST) models which included nonlinear dependencies of cod catches from T and D have the best generalization ability. Correlation between predicted by VAST models and observed distribution density of cod in the test data set are higher than that in simpler models trained using the full set of data. The VAST models produce continuous time series of cod biomass with estimates of their uncertainty and statistical weights of the model configurations relative to the test data. After stacking with statistical weights and previously published estimates of biomass, the obtained time series allow to estimate dynamics of biological processes deviations from stationary assumptions and to estimate approximately the volume of “extra” cod not considered by these processes in the Bayesian State-Space Surplus Production Model. The portion of “extra” cod increased sharply above 40 % in 2016 and reached the maximum of 49 % by 2018, then began to decrease. Sharp changes in the main EOF modes for T are revealed in these years. Thus, the hypothesis of cod redistribution in the Bering Sea due to changes of the cold pool area at the bottom was tested for the first time by statistical methods in space. Due to high errors of forecasts based on analysis of biological processes only, there is impossible to predict accurately dynamics of the cod biomass without predicting the water temperature distribution at the bottom of shelf.