Japanese sardine stock assessments in the North-West Pacific are overviewed for the past 10 years on the data of research surveys by midwater trawls in the area at the Pacific side of Kuril Islands in 2014–2024 and fishery statistics. The feeding schools of sardine began to enter the waters at Kuril Islands in 2014, these migrations had significant seasonal and interannual dynamics during the decade under influence of oceanographic conditions in the zone of warm and cold currents interaction. The Russian fishery of sardine started in 2016 and continued until nowadays, with the maximum annual catch recorded in 2024.

   Size and age structure, linear growth and maturation are considered for eight mass flatfish species in the Karaginsky and Olyutorsky Bays (southwestern Bering Sea) on the data of size measurements and biological analyses in catches and the results of age determination by otoliths. Asymptotic patterns are determined for their growth, with the maximum gains of 4–6 cm per year in the first 3–4 years of life. Sexual dimorphism in linear growth rate with females larger than males is observed for all investigated species. The earliest size difference is noted for alaska plaice — by the end of the first year of life, and the latest for longhead dab — by the age of 6 years. Longhead dab and sakhalin sole reach the body length close to the highest limit earlier than other species; length of their males and females exceeds 90 % of the maximum values in 7 and 10 years for the former species and 8 and 11 years for the latter one, respectively. The longest life expectancy is detected for starry flounder (38 years) and rock sole (31 years), the shortest — for longhead dab (age of the oldest fish did not exceed 15 years). Yellowfin sole, rock sole, and juvenile starry flounder grow faster in the Karaginsky and Olyutorsky Bays than the same species in adjacent areas of the Bering Sea and shelf of Kamchatka. On the contrary, sakhalin sole and longhead dab grow slower in these bays than on the western and eastern Kamchatka shelves. Starry flounder form two ecological groupings in the Karaginsky Bay with different growth rate. After 4–5 years of common life in the coastal zone, one group of this species migrates to greater depth on the shelf where they grow faster than fish in another group that remains at the coast. Longhead dab become mature earlier than other species; 50 % of their females reach sexual maturation at the 4th year of life with the length of 23.0 cm. Alaska plaice and flathead sole are distinguished by the slowest maturing and reach the same level of puberty on average in the age of 9.0 and 9.3 years with the length of 35.0 and 35.3 cm, respectively. The results obtained are useful for the stocks assessment and in population studies of these species.

   Hierarchical classification of the sublittoral vegetation in the Russian Far Eastern seas is presented for the first time. Like other marine areas of temperate and high latitudes, this region is characterized by dominance of certain species, higher taxa, or ecological groups of vegetation that allows to use the concept of adaptive zones for the classification. The vegetation cover represents a multi-level mosaic of adaptive zones, with the dominants in certain areas belonged to taxonomic and ecological groups of various rank. Such structure gives a natural ecological basis for the hierarchical classification of vegetation displayed as a prodromus — a list of assemblages, accompanied with information on their location and habitat. The assemblages are described in accordance with requirements of the International Code of Phytosociological Nomenclature; their dominants are listed as diagnostic species. The prodromus includes 113 syntaxa: 66 associations, 33 unions, 9 orders, and 5 classes, and will be expanded through further research. The adaptive zone concept provides the minimum number of syntaxa, eliminates subjectivity in their identification, brings the syntaxa system as close as possible to the natural classification, and enables unambiguous identifying the assemblages. The prodromus is suitable as a field guide. The results demonstrate applicability of this approach for classifying marine vegetation in other regions, too, at least in temperate and high latitudes.

   Spatial distribution of fish species was surveyed in Lake Lebedinoye (Iturup Island) in September and October 2025 with fry seine (20 m long, 1.5 m high, 4 mm mesh size). The ichthyocene was predominantly represented by amur stickleback Pungitius sinensis, with a small portion (up to 3–5 %) of juvenile big-scaled redfin Tribolodon hakonensis. Weight of the redfin juveniles varied from 50–100 mg to 5–6 g. Abundance of two main fish species and their ratio were rather stable by stations and during the whole period of survey. Japanese smelt Hypomesus nipponensis were presented in 18.7 % of catches, but 18–22 individuals of the species with various size were in each of these catches. Single specimens of juvenile starry flounder Platichthys stellatus were caught occasionally in different parts of the lake, which were not observed there previously, though ability of marine flounders to enter fresh water bodies is known. A juvenile of the introduced prussian carp Carassius gibelio was caught for the first time in Lake Lebedinoye that was a clear sign of this species reproduction in the lake, although very limited. Japanese huchen Parahucho perryi were not detected at the coast in September but appeared after October 7, when the water temperature at the surface of the lake did not excess 14.1 оC and dropped to 8.0 оC at the mouth of the Rybovodny stream. Besides the fish, shrimp Palaemon paucidens and mysid Neomysis awatschensis were caught occasionally in different parts of the lake; the shrimp biomass was sometimes comparable with the biomass of amur stickleback.

   Yearlings (0+) of coho salmon Oncorhynchus kisutch (19450 ind.) and masu salmon Oncorhynchus masou (3000 ind.) were released into the Kuchelinova River upstream of the Kuchelinovskoye Reservoir on July 15, 1987. The juveniles of both species were transported from the Ryazanovsky Experimental Salmon Hatchery. Results of these species monitoring in the basin of reservoir in 1987–1991 and 2020–2025 are presented.

   New data on distribution of masu salmon jacks in the waters of Prymorye Region are presented. Scales of three masu salmon jacks (two from the Serebryanka River and one from the Samarga River area) were analyzed. Age and previous maturation as parr were estimated. In the Serebryanka River, masu salmon were represented by two previously known life history forms: the jack that did not mature in the river as parr, and the jack previously matured as dwarf male. Compared to masu salmon from the rivers of southern Primorye, the specimens found in northern Primorye were larger: their fork length ranged from 345 to 403 mm.

   Interannual dynamics of total dissolved phosphorus (DTP) in habitats of marine coastal plant communities of Peter the Great Bay (Japan Sea) in the summer seasons of 2017–2024 were analyzed using hydrochemical and statistical methods. The pattern of DTP variations in Amur Bay was found to be nonlinear: DTP increased, on average, 3-fold in each 4th summer season compared to the minimum level of 0.03 mg/L (1.0 μM) that had been observed unchanged for the previous three years. The DTP contents in Ussuri Bay and in the Stark Strait had similar average values (approximately 3-fold lower than in Amur Bay) throughout the study period. In the Stark Strait, the DTP content remained at the same level, while in Ussuri Bay, it showed a slight tendency to decrease. Periodic rises in DTP content in the coastal waters of Amur Bay can be manifested as increases in primary and secondary
production in the coastal ecosystems of the bay.

   Catch dynamics of chum and pink salmon in the Sakhalin-Kuril Region did not correlate positively with the changes in their juveniles release from salmon hatcheries — the catches grew after the release of 500–600 . 106 ind. but decreased when the higher volumes were released. The effect of artificial reproduction of juveniles on the stocks of pink salmon was insignificant, so far as the fish from natural spawning grounds provided > 95 % of the catches in eastern Sakhalin. For chum salmon, the artificial reproduction was effective when the juveniles release did not excess 100 ^. 10⁶   ind. in Iturup Island, 200–250 ^. 10⁶ ind. in eastern Sakhalin, and 70 . 106 ind. in southwestern Sakhalin. So, the salmon hatcheries activity in the Sakhalin-Kuril Region requires adjustments to resolve contradictions between the natural environments and economic activities in the salmon water bodies; between the desired short-term and long-term economic outcomes and approaches to planning; between the fishery industry focused on exploiting natural stocks and the aquaculture developing the hatchery reproduction; between the mostly natural reproduction of pink salmon and predominantly artificial reproduction of chum salmon; and between the trends in salmon stocks dynamics in the Sakhalin-Kuril Region and generally in the Russian waters.

   The main reasons for decline in the stocks of commercial species in Sea of Azov are considered for a present stage. Effectiveness for the measures of the stocks restoration is assessed, including the measures for compensating the negative impact of dredging in ports. Possibilities of restoring the biocenoses through artificial reproduction of certain species and fishery melioration are discussed. Evaluation the harm to aquatic biological resources and compensation for the damage are faced with numerous difficulties and contradictions that can only be overcome with appropriate biological and economic justifications. Development of fundamental foundations for such justifications is an important scientific and practical task.

   Experiment on growing 40 Australian red-claw crayfish Cherax quadricarinatus was conducted in the open pond with the area of 51.84 m² and depth of 1.8 m located in the Moscow Region during 93 days from June 10 to September 10, 2024. Water temperature and DIN concentration (NH₄⁺, NO₂^–, NO₃^–) were monitored in the pond. The highest temperature (most favorable for redclaw) was observed at the depth of 0.5–1.0 m (19–26 ^оC), the temperature at the depth of 1.5–2.0 m was lower (17–23 ^оC); the average temperature in the whole 0–1.8 m layer was 20.6 ^оC. The body length and weight of redclaw were measured. These parameters had increased in 3 months on average by 34.40 mm (148 %) and 19.59 g (298 %), respectively. The average daily weight gain throughout the entire period was evaluated as 0.210 g/day. The growth rate of redclaw in the experimental open pond was in 2.5–3.0 times higher than the growth of the same species in recirculating aquaculture systems. The results obtained demonstrate clearly possibility for cultivation of redclaw in ponds of the Moscow Region using their natural food resources.

   Nutritional and biological value is investigated for frozen and canned meat of bearded seal. The two types of canned products contained 84–88 % meat with addition of vegetable oil, onions, and spices and were sterilized using standard modes ensured sterility and storage ability. Chemical composition was considered in detail for these canned products. The content of protein exceeded 20 %, with the summary content of essential amino acids 43 g/100 g of protein. The limiting amino acids were sulfur-containing ones, as usual for marine fish and fish products. Triacylglycerols dominated in the fat with the total amount of 86.7 %. The portion of monounsaturated fatty acids was 58,2 % of the total fatty acids. The PUFA content was 22.17 %, mainly omega-3 PUFAs (18.57 % or 1.42 g PUFA per 100 g of canned food), with the sum of EPA and DHA at least 1.0 g/100 g that corresponded to the recommended intake of essential fatty acids for adults. By the indices of lipid quality determined as the ratio of saturated and unsaturated fatty acids, these canned products are able to reduce the cholesterol level in blood and the rate of thrombus formation in blood vessels of human. Besides, the canned meat contains large amount of iron and selenium, so it can be recommended for reducing the deficiency of these elements.

   Methodological approaches used in the Sakhalin branch of the Russian Federal Research Institute of Fisheries and Oceanography (SakhNIRO) for quantitative assessment of pacific salmon (Oncorhynchus) juveniles in the rivers of Sakhalin Region are analyzed critically. Methodic and logical problems are revealed that worsened the results reliability. The linear interpolation used for time correction of cross-sectional distribution for juveniles of pink salmon Oncorhynchus gorbuscha in a control river gives sometimes unrealistic negative values when actual catches are not zero, that means the algorithm has limited applicability. Ways for methodological improvements are proposed, including formalization of computing procedures, implementation of quality control at certain stages, and data verification and validation. Without these measures implementation, the current methodology does not ensure standardization of calculations, so cannot serve as a reliable basis for monitoring the juveniles abundance.