The aim of the research was improvement of the algorithm of age determination for red king crab males in the Barents Sea, by taking into account the molting probability.

Materials were the data of research surveys and fisheries monitoring obtained in 2001–2022 and combined in 54 data sets, as well tagging data published in open press.

As results the previous algorithm which allowed establish the age composition of the red king crab males catches was improved. The parameters of the model of the dependence of the probability of molting on the width of the carapace, which was established earlier according to the tagging data, were changed. The modified model allowed to improve the adequacy of the estimates by reducing the values of the approximation error. Compared to the previous estimates of the age composition, the account of the probable molting history did not lead to a significant revision of the results: all noticeable generations remained the same as before, the time for recording a generation in catches however increased from 10 to 12 years. The parameters of the proposed model are the closest to those for the Kikhchik subpopulation of the red king crab off the Western Kamchatka. The contradiction associated with the discrepancy in the assessment of the maximum age of both the generation and individual specimens is discussed.

Practical value. The obtained results can be applied for the red king crab stocks assessment with the help of cohort models.

The aim: the characteristics of sturgeon fish that make seasonal migrations to the near-shore zone of the Azov Sea.

Material — scientific monitoring of commercial fishing with stationary seines in the water area of the Sea of Azov adjacent to the Primorsko-Akhtarsk district in October 2022, 2023 and April 2023, 2024.

The results: Russian Sturgeon and Starry Sturgeon (Sevruga) were encountered in stationary seines from 50% to 100%, and the average catch of these species per facility was 1.3–7 sp./day in the autumn and spring periods, respectively. In the fall of 2022, the prevalence of Sevruga in bycatch was almost double — 63% of the total bycatch; in the spring and fall of 2023, 2024, the superiority was with Sturgeon — 63–83% of the bycatch. Size range of Sturgeon in 2022–2024 was from 22 to 148 cm; Sevruga — from 23 to 123 cm. The weight range of Sturgeon was from 0.1 to 30.0 kg, Sevruga — from 0.2 to 7.8 kg. The share of fish that reached the commercial length was on average 20.7% of Sturgeon and 36.6% of Sevruga. The age of the fish varied from fingerlings to 16+ for Sturgeon and up to 8+ for Sevruga. The average fullness coefficient of Russian Sturgeon in the autumn was 0.72; in spring, — 0.79; Sevruga: in the autumn of 2022 and 2023–0.45, in the spring of 2023–0.58. The state of Russian Sturgeon in the near-shore aggregations indicates the formation of its full-fledged mixed-age population in the Sea of Azov, that allows to expect its commercial fishing in the near future, on the background of the increasing its stock. The state of the Sevruga requires more in-depth research. A high fish fatness coefficient indicates their sufficient food supply.

Practical value: Observations of bycatch in stationary seines in the near-shore area of the sea are an important addition to the accounting trawl survey data for understanding the structure of the Russian Sturgeon population in the Azov Sea and practically the main source of information on the state of the Sevruga population.

The purpose of the work is to perform a quantitative comparative analysis of the structure and size of annual rings of chum salmon scales to prepare a methodological manual for determining age. The research material included scale preparations from 493 chum salmon producers of different ages, on which sclerites were counted and the diameter of annual rings was measured.

Methods used: comparative data analysis, descriptive statistics methods.

Results: it was found that the size of the scales, the size of each of the annual rings, as well as the number of sclerites in the annual rings of male and female chum salmon within each age group do not differ. The number of sclerites forming each annual ring, as well as the radius of the rings, varies significantly among different individuals. With age, as the length and mass of fish increase, the size of the scales naturally increases. Moreover, an acceleration in the growth rate is observed during the year preceding puberty. As a result, the number of sclerites in the last annual ring, as well as the size of this ring in fish that reach sexual maturity is always greater than in fish of the same age, but remaining in the sea to continue feeding.

Practical significance: the presented article is a scientific accompaniment of a methodological manual for the practical determination of the age of chum salmon by scales.

The purpose of the work was to give as complete an overview as possible of the currently available publications related to the nutrition of the Baikal seal (Pusa sibirica).

More than 50 sources devoted to the stated topic served as materials for writing the review.

The results of the analysis of published sources showed that the Baikal seal feeds mainly on 4–6 species of small pelagic fish throughout the year, and the main food is two species of golomyankas of the Comephoridae family. The hypothesis according to which the well-being of the species is largely determined by the use of the pelagic crustacean Macrochectopus branickii for food does not stand up to criticism and is unlikely to reflect the real picture. The distribution of the Baikal omul is such that it does not exclude, but does not in any way contribute to the fact that the seal consumes it in significant quantities. However, the consumption of salmonids as food has become more frequent in recent years (the reasons for this cannot be established), but even now these fish constitute <3% of the biomass of fish consumed by the entire population of the Baikal seal per year. All adaptive morphophysiological, anatomical and behavioral features of the species clearly indicate that the seal has developed a food strategy aimed at the effective production and utilization of the above-mentioned fish species.

Conclusion: the basis of the diet of the Baikal seal is made up of small non-commercial pelagic fish species, therefore, even with a large population, seals cannot be the reason for the reduction in commercial omul stocks.

The practical significance of the work lies in the fact that its conclusions must be taken into account when developing rules and strategies for exploiting the Baikal seal population.

Purpose of the review: analysis of the effect of the photoperiodic factor based on indicators of lipid metabolism in Salmonid and Cyprinid fish species.

Methods used: comparative analysis of literature and own experimental data.

Results: The length of daylight (photoperiod) is one of the most important abiotic factors affecting the behavior, reproduction, metabolism, growth and development of fish. The changes in the lipids and fatty acid constituents execute a significant role in the adaptation of aquatic organisms to new light conditions. Certain parameters of lipidogenesis can serve as a reliable indicator of the normal route of metabolic processes in the organism. It is widely known that photoperiod regimes are used in aquaculture to optimize the cultivation of various species of aquatic organisms, including the most common Cyprinids and Salmonids. The specificity of the reaction of lipid metabolism to the effects of various lighting modes is shown: in cyprinids, the reaction can be multidirectional depending on the species (including its absence), while in Salmonids on example of Atlantic salmon, a change in the lipid profile in the direction of smoltification is observed. The role of combining the photoperiod with other factors, such as feeding and climatic features of the region, are discussed.

Significance: The results can contribute to a better understanding of the adaptive processes in fish and optimize the conditions for their artificial rearing.

The purpose of the work: improvement of methods of fish number accounting in growing cages and reservoirs of fish farms using hydroacoustic tools and information technologies.

Methods used: solving the problem of non-contact (non-invasive) measurement of the number of fish in cages using the hydroacoustic echo integration method. Investigation of the reflective properties of fish using a calibrated scientific echo sounder with a split beam. Carrying out measurements with different numbers of fish in cage. Identification and analysis of factors affecting the accuracy of the echo integration estimation of the number of fishes in cage.

Novelty: the elements of novelty are the use of a scientific echo sounder with vertically oriented antenna and split beam to estimate the number of fishes in cages, the algorithm for calculating the number of fishes in cages by the echo integration method, the results of the study of reflective properties of Amur carp and identified optimal measurement conditions that allow hydroacoustic estimates of number with maximum accuracy.

Results: the dependences of target strength on the linear size of Amur carp are obtained. An algorithmic scheme for calculating the number of fishes in cages by the hydroacoustic echo integration method has been developed. Experiments were carried out with different numbers of fish in the cage. It is established that the main factors affecting the accuracy of the population estimate are the number of individuals in the cage and the daily distribution of fish. Measurements at night and at concentrations above the threshold (50 pcs./m²) can significantly bring the estimated and true numbers of fish in the cage closer and reduce the variability of density estimates.

Practical significance: solving the problem of remote measurement of the fish number in growing cages will allow farmers to optimize feed needs, which, in turn, will ensure rapid growth of fish without overfilling it and not polluting the reservoir.

The aim of the work is to determine the influence of sea water circulation and temperature on the formation of the spawning stock of anchovy in the Sea of Azov.

Materials and methods: Fishery and biological data on the spawning stock of the Azov anchovy were collected in surveys and bioresources monitoring carried out by the Azov-Black Sea branch of the VNIRO («AzNIIRKH») in 2000–2021. Satellite sea level data were used in the analysis of sea water circulation. These data, as well as satellite information on sea surface temperature for March-June 2000–2021 for the north-eastern part of the Black Sea and the southern part of the Azov Sea were taken from the website of the Copernicus Marine Service information system. Graphical and statistical methods of analyzing multi-year changes in the data were used in the work. The novelty of the performed work lies in the study of oceanographic conditions of spring migration of anchovy to the Sea of Azov as factors determining the size of its spawning stock in this sea.

Result: intensive growth of the spawning stock of anchovy in the Sea of Azov was observed in 2008, 2010 and 2011. This was facilitated by: predominance of north-western geostrophic currents in the north-eastern part of the Black Sea in April 2008–2011, weakening of the Azov currents in the Kerch Strait in April 2007–2010 and predominance of the Black Sea currents in May 2004–2012, Decrease in the meridional gradient of water temperature in the Kerch Strait in April 2007–2010.

Practical significance: the possibility of using oceanographic information for April-May to predict the size of the spawning and commercial stock of anchovy in the Sea of Azov.

The aim of the paper is to assess interannual and decadal variability of the Barents Sea and Arctic ice extent in various seasons for the period from 1979 to 2022.

The material for the study was satellite data on the Barents Sea and Arctic ice extent, climate indices, oceanographic data obtained during surveys in the Barents Sea by PINRO and other available information on hydrometeorological conditions of the sea in 1979–2022.

Methods of descriptive statistics as well as comparative, correlation, regression, harmonic and cluster analyses were applied.

Results: The year-to-year changes in the Barents Sea and Arctic ice extent in various seasons are described for 1979–2022. The modern climate changes, manifested in substantial warming of air and water masses in the Arctic, resulted in a considerable ice extent reduction in the studied areas in recent decades. Well-marked negative trends took place in all months and seasons. The annual mean ice extent was decreasing at a rate of 532 thousand km² per decade in the Arctic, and at a rate of 105 thousand km² per decade in the Barents Sea. Over the past 40 years, the ice extent in the Arctic has decreased by 14%, and in the Barents Sea — by half (by 51%), while the ice-free period duration has increased in the Barents Sea from one to three months. Hydrometeorological parameters were identified that are most closely related to the ice extent in the Arctic (|r| ≥ 0.40) and Barents Sea (|r| ≥ 0.60). Reliable regression models were developed that explain 45.2 and 88.0% of its variability, respectively. The contribution of individual factors to the ice extent variability explained by regression equations was quantitatively assessed, and the leading role of air temperature was noted.

Practical significance: The obtained results are useful for a better understanding of the climate processes occurring in the Arctic and Barents Sea in recent decades and can be used to assess the impact of climate changes on the main objects of Russian fishery in these areas.

The study aims at discovering features of seasonal changes in the mixed layer depth (MLD) of the Barents Sea in 1993–2020.

Charts of the distribution of the MLD in the Barents Sea in 1993–2020 provided by the Copernicus Marine Service were used as the material of the study.

Methods of the study: cluster analysis, machine learning, neuronal networks, the nearest neighbor method (kNN).

Results. Classification of the data sets of the MLD distribution according to their seasonal features was carried out based on the modelling using AI algorithms and machine learning. It was concluded that winter is specified by two classes (increased/decreased values of the layer thickness). The third class includes spring and autumn when distributions of the MLD are close to one another, and the fourth class comprises summer (June-September) when the MLD grows very slowly.

Practical relevance. The results will contribute to a better understanding of the hydrophysical processes of the Barents Sea and can further be used as series of independent variables to study the Barents Sea ecosystem and to estimate a stock and a catch forecast of commercial aquatic organisms.

The purpose of this work is to develop technological parameters for the hydrolysis of barrel jellyfish Rhizostoma pulmo involving the use of enzymatic agents «Enzy-mix» and alcalase, available through the domestic market, as well as to investigate the amino acid and mineral composition of the resultant hydrolysate.

Methods used: the process of hydrolysis has been assessed based on the changes in peptide concentrations in the hydrolysate, the content of amino nitrogen, and the degree of hydrolysis. To investigate its chemical, amino acid, and mineral composition, the standard methods were used. Novelty: the use of jellyfish for hydrolysis after its thawing and the hydrolysis procedure not involving the addition of water into the raw material subjected to hydrolysis present a novel approach.

Result: the optimal regime for hydrolysis of barrel jellyfish Rh. pulmo after its thawing has been identified, which was characterized by the use of 1% alcalase at the temperature 55±2 °C and duration of 1 h. It has been shown that alcalase is more effective in terms of amino nitrogen accumulation than enzymatic agent «Enzy-mix». The values of amino nitrogen after 1 h of hydrolysis involving the use of 1% alcalase were higher than the values of the same parameter obtained during the 3-hour hydrolysis involving 1.5% «Enzy-mix» at the temperature 40±2 °C. The hydrolysate, after its concentration to the dry matter exceeding 30%, contains no less than 15.1±0.59% of protein represented by 48% of essential amino acids, out of which leucine and isoleucine prevail (15 %). Among non-essential amino acids, the most prominent was glycine (17 %). For all essential amino acids, except for valine, the amino acid score exceeds 100%. In humans, consumption of around 20 g of the hydrolysate covers the daily physiological requirement of magnesium.

Practical significance: the obtained data on the amino acid profile and mineral composition of the barrel jellyfish Rh. pulmo hydrolysate provide the basis for its consideration as a promising ingredient for the functional nutrition products.

The aim of the work is to develop theory and practice of sustainable fisheries.

Used methods: abstract-logical approach, in particular, deduction and induction methods, analysis and synthesis, which made it possible to determine the essence of the concept of “sustainable fisheries”, highlight its features and system components, assess the development trends of world fisheries and aquaculture, develop a conceptual model of sustainable fisheries.

The novelty of the study results lies in the identification of sustainable fisheries as an independent scientific economic category, clarification of its meaning, the creation of a new approach to the formation of the value chain of fish products in sustainable fisheries, and the development of a conceptual model of sustainable fisheries.

Results of the study: the work characterizes sustainable fisheries in the context of its lack of alternative on the path to sustainable development; the functional classification of environmental goods and services is emphasized and the need to include them in the value chain of fishery products is justified; such system elements of the conceptual model of sustainable fisheries as its mission, goals, methodological basis, key factor, principles and tools are highlighted.

The practical significance of the study is determined by its consistency with the general trend of industry development, which is based on an ecosystem approach to fisheries and aquaculture and a focus on achieving the goals of sustainable development of society.

The purpose of the work is to analyze current trends in the development of the Russian fisheries complex and identify the causes of the stagnant dynamics of consumption of fish products by the population.

Methods used: general scientific research methods, as well as methods of statistical analysis of time series, graphical and coefficient methods.

The element of novelty: The current interdependence between the dynamics of fish catch, the actual financial results of economic activities of enterprises, as well as the general level of consumption of fish products by the population has been revealed. The study based on quantitative analysis complements the existing economic theory with new empirical data necessary to clarify the current directions of development of the country’s fisheries complex for its sustainable development.

The results of the study: the actual catch of fish in Russia, which reached its historical maximum in modern history of 5.3 million tons in 2023, with simultaneously high levels of exports of fish products, provided an increased level of profitability of economic activities of enterprises and an increase in their financial independence in comparison with other sectors of the economy, however, the studied trends in the development of the fisheries complex were not broadcast in advance the increase in consumption of fish products by the population, in particular, from 2010 to 2022.

Practical significance: the obtained research results and empirical data can be used by the authorities in developing relevant directions for the sustainable development of the country’s fisheries complex.

The purpose of the work: Conduct an integrated assessment of the economic efficiency of commercial fish farming.

Materials and methods: The information base of the study was made up of statistical and operational materials on commercial fish farming of the Central Federal District of Russia (CFD) for 2015–2021. The main research methods were the monographic method, the method of analyzing the production and economic activities of the Central Federal District through scientific approaches, as well as the method of interpreting the results of the study.

The result based on the developed methodology, an analysis of the economic efficiency of commercial fish farming in the Central Federal District of Russia (CFD) was carried out on the basis of the use of a complex (integral) indicator, which allowed identifying the main factors affecting the level and dynamics of the economic efficiency of commercial fish farming in the CFD. The degree of influence of particular indicators on the economic efficiency of production is shown — labor productivity, material output, capital.

The practical significance it is possible to use a complex indicator in the analysis of production and economic activity, which allows determining reserves for improving the efficiency of using production resources — living and past labor. The complex indicator can also be used in the development of current options and long-term production plans, followed by the selection of the most effective option.

Purpose: based on long-term data on the dynamics of fish catches and foreign trade in fish products, as well as international comparisons of world fishing powers, analyze the prospects for the development of the domestic fishing industry in the new economic conditions of sanctions confrontation with the countries of the collective West.

Method: used such methods of general scientific knowledge as analysis and synthesis, as well as comparisons, tabular and graphical methods.

Novelty: a detailed assessment of the factors affecting the growth of domestic fishing and fish farming, including the development of the domestic fishing fleet, was made. The prospects for expanding the sale of fish products on world markets, including on the basis of data on current and prospective consumption in different regions of the world, were considered.

Results: the study analyzed a number of sources, including FAOSTAT and Rosstat commodity resource balances, in terms of production, consumption and cross-border trade in fish products. It has been established that after 2014 own consumption and imports are declining, while exports, on the contrary, are gradually increasing. Thus, the main driver of production growth in the industry is expansion to foreign markets. In the context of strengthening anti-Russian sanctions policy, it is necessary to diversify the sales markets for Russian fish products, however, an outdated production base is a significant limitation for the development of the industry.