CONTENT
Environmental Concerns and the State of Aquatic Environment
Burdina E.I., Kosenko Yu.V., Anokhina N.S., Bragina T.M., Gorgola L.G.
Abstract
Background. The Lower Don area is experiencing significant anthropogenic impact, which leads to the transformation of natural landscapes, deterioration of water quality, depletion of biodiversity and other adverse processes. Relevance. Semikarakorsky District is one of the leading agricultural hubs of the Rostov Region, where irrigation farming is practiced. Heavy water use in its area and other anthropogenic factors exert considerable impact on the quality of the Don River water as a living environment for aquatic biological resources. The aim of this work is to analyze hydrochemical and toxicological parameters of the Lower Don River ecosystem in late spring 2025 near Semikarakorsk, Rostov Region (sampling point 3). This article continues a series of publications on the results of monitoring the quality of the living environment for aquatic bioresources in the Don River. Methods. Sampling of water and sediments to determine chemical parameters was conducted using standard methods. Chemical analysis was performed in accordance with practices approved at the federal level. Results. Oxygen oversaturation (112 %) resulting from intense phytoplankton photosynthesis was observed in the Don River section near Semikarakorsk. In terms of its trophic status, the water was characterized as hypertrophic (6.5 units). Water samples revealed elevated concentrations of iron (3.3 MACfishery), manganese (6.8 MACfishery), and copper (2.5 MACfishery), which could be a consequence of the high trophic status of this water body. Bottom sediments showed a 50-fold increase in the content of petroleum products compared to 2024, while manganese and cadmium concentrations were twice the long-term average. Conclusion. Elevated levels of certain metals (iron, manganese, and copper) in the water column and bottom sediments of the Don River near Semikarakorsk could result from the natural processes within this water body. In the case of other toxicants (cadmium, petroleum products), there is a high probability of their anthropogenic origin linked to economic activity in the region, which has led to the deterioration of the habitat of benthic biocoenoses.
Keywords: Don River, Semikarakorsk, hydrochemistry, toxicants, petroleum products, habitat, bottom sediments, aquatic bioresources
Ocherednik V.V., Zatsepin A.G., Fedorova P.A.
Abstract
Background. This paper presents the results of a quantitative assessment of the thermal balance of a 25-meter water layer on the near shelf of the northeastern part of the Black Sea. This study involved a comparison between the actual heat content, calculated from direct measurements of the vertical temperature distribution, and the virtual heat content, determined in a one-dimensional approximation through the total heat flow at the “water–air” interface using NCEP CFSv2 atmospheric reanalysis data. Relevance. The estimation and comparison of the actual and virtual heat content confirmed the hypothesis that heat exchange occurs between the inner shelf and the deeper sea zone. In the spring and summer period, the actual heat content was lower than the virtual one due to the outflow of warm water from the inner shelf, and in the autumn and winter it exceeded the virtual one owing to the influx of warm water from a deeper zone. The aim of this work was to compare the values of actual and virtual heat content in the spring–summer and autumn–winter periods. Methods. The field data were obtained using a thermistor string designed and created at the Southern Branch of the P.P. Shirshov Institute of Oceanology of Russian Academy of Sciences (Southern Branch of the IO RAS), and atmospheric reanalysis data from NCEP CFSv2 were also used. Results. An analysis of the obtained data showed that the thermal structure of the active water layer on the inner shelf of the monitoring site “Gelendzhik” is characterized by pronounced seasonal variability: the vertical temperature profiles revealed the formation of an upper quasi-homogeneous layer and a seasonal thermocline in spring and summer, and its destruction in autumn and winter due to vertical mixing. Conclusion. The obtained results highlight the need for further improvement of methods for assessing the thermal balance of the active water layer and the importance of high-precision measurements of vertical temperature distribution by thermistor strings for studying hydrophysical processes in the shelf zone.
Keywords: Black Sea, heat content, active layer, thermistor string, NCEP CFSv2 reanalysis
Biology and Ecology of Aquatic Organisms
Borodina A.V., Velyaev Yu.O., Pimenov K.A.
Abstract
Background. The sea snail Tritia reticulata (netted dog whelk) is a widespread species of carnivorous gastropods of major ecological importance, as it participates in the transfer of nutrients and energy between different ecosystems. Relevance. The patterns of lipid and fatty acid accumulation in this species remain poorly studied, contributing to the relevance of related research. The aim of this article is to present the results of a study on changes in the lipid complex (total lipids (TLs), phospholipids, diglycerides and sterols, free fatty acids, triacylglycerols (TAGs)), as well as the fatty acid (FA) composition and total carotenoid content (TCC) in an experiment involving food deprivation of the sea snail T. reticulata. Methods. The analysis was performed using chromatography and chromatography-mass spectrometry techniques. Results. Following a 3-week period of feeding snails with the meat of the bivalves Chamelea gallina and Cerastoderma glaucum, TL content increased more than twofold, primarily due to an increase in TAGs (1.85-fold). Meanwhile, TCC decreased by 23 %. The number of identified FAs increased from 26 to 34, mainly due to an increase in monounsaturated FAs (MUFAs) and polyunsaturated FAs (PUFAs), thereby enhancing the nutritional value of this hydrobiont. Ten FAs not present in the food source were found to accumulate in the snails: C13:0, C14:1n-5, C14:1n-3, C17:1n-7, C19:1n-9, C20:4n-6, C21:5n-3, C22:5n-3, C22:2n-6, C22:2n-9. Conclusion. This diet led to an increase in TLs and valuable PUFA content in the snail meat, without affecting the omega-3/omega-6 fatty acid ratio. This mollusc can serve as a source of PUFAs essential for human nutrition.
Keywords: sea snails, Tritia reticulata, lipids, fatty acids, food deprivation, Black Sea
Ichthyofauna of Marine and Inland Water Bodies
Karnaukhov G.I., Yatchenko V.N., Vasilyev A.A.
Abstract
Background. The involvement of multipurpose water bodies in fisheries exploitation not only stimulates the creation of new employment opportunities and improves regional economic infrastructure, but also contributes to the additional production of animal protein and the implementation of programs for rational environmental management. This article examines the current state of the fishery resource base of multipurpose water bodies in the Krasnodar and Stavropol Territories, the Republics of Adygea and Kalmykia, and the Rostov Region. Relevance. The Strategy for the Development of the Fisheries Complex of the Russian Federation for the period up to 2030 provides for increased efforts to enhance the production and conservation of aquatic biological resources to ensure national food security, which is possible only on a scientific basis that includes knowledge of the population structure of commercial species and estimations of the abundance and biomass of commercial fish stocks for their rational exploitation. The aim of this work is to assess the state of stocks of the major commercial fish species, as well as to determine the commercial fish productivity of multipurpose water bodies over the past 15 years. This goal was accomplished by solving the following tasks: providing a general fisheries description of the investigated subjects; assessing the length–age composition and the key growth parameters of commercial fish species; and analysing the fish productivity of the water bodies during their fisheries exploitation. Methods. Ichthyological samples were collected and processed according to generally accepted methods. The calculations of abundance and stocks were based on the method of direct quantitative count per unit area. Results. Long-term studies of multipurpose water bodies over the period from 2010 to 2024 made it possible to characterize the current composition of commercial ichthyofauna. As a result of the conducted studies, it has been found that formation of the commercial ichthyofauna is required, with the introduction of species that can utilize unused feed resources in the water bodies and significantly enhance their fish productivity. The main direction of fisheries exploitation of the water bodies has been identified. The stocks of the major commercial species have been characterized. Based on the analysis of estimates of exploitable fish stocks, a comparison of the fish productivity of the investigated water bodies has been performed. Conclusion. The conducted studies have shown that commercial fish stocks in the multipurpose water bodies currently remain almost at the same level. However, qualitative changes in the ichthyofauna composition are occurring due to an increase in the proportion of low-value species, namely crucian carp and perch. To increase the stocks of valuable fish species (zander, common carp, and Northern pike), it is necessary to carry out their artificial reproduction for the subsequent stocking of the water bodies.
Keywords: multipurpose water bodies, ichthyofauna composition, exploitable stocks, fish productivity
The finding of the ship sturgeon Acipenser nudiventris Lovetsky, 1828 in the Azov Sea.
Luzhnyak V.A., Nebesikhina N.A., Shelestyukova A.A.
Abstract
Background. Among all sturgeon species historically inhabiting the Azov Sea, the ship sturgeon Acipenser nudiventris had the most extensive range, including the Azov–Black Sea, Caspian Sea, and Aral Sea Basins. As a result of regulation of spawning rivers and heavy exploitation, this species has disappeared from most of its range. Natural reproduction of the remaining scarce populations cannot ensure their sustainable abundance. Relevance. The disappearance of the ship sturgeon from most of its native range contributes to the relevance of its artificial reproduction for the preservation of its gene pool and restoration of its populations in the lost parts of its range. The aim of this work is to describe a new record of the ship sturgeon in the Azov Sea. Methods. Information about the new discovery of the ship sturgeon was obtained during the monitoring of coastal fishing using stationary pound nets in the Azov Sea in the autumn of 2025. Results. This sturgeon species has not been recorded in the Azov Sea Basin since the beginning of the 20th century and was considered extinct by earlier researchers. This is the first reliable record of the ship sturgeon in the Azov Sea in the last 100 years. Сomparison of the nucleotide sequence of the mitochondrial DNA control region (D-Loop) of the investigated specimen with the data from the gene bank and the general database of mitochondrial haplotypes of A. nudiventris of the Russian Federal Research Institute of Fisheries and Oceanography (RSC RF FSBSI “VNIRO”), as well as its microsatellite profile, indicates that this specimen belongs to the species A. nudiventris. Conclusion. The appearance of the ship sturgeon in the Azov Sea results from its reacclimatization efforts in the Kuban River Basin and the release of breeders and juveniles of this species in natural waters.
Keywords: ship sturgeon Acipenser nudiventris, range, Azov Sea, mtDNA D-Loop
Fisheries and Processing of Aquatic Bioresources
Stafikopulo A.M., Аndronov V.А., Vtyurina N.V., Gorbatyuk Ya.I.
Abstract
Background. In recent years, a notable increase in the population of the invasive ark clam species, half-crenated ark Anadara kagoshimensis, has been observed in the Azov Sea; its communities have spread across almost the entire sea area. In 2024, a recommended catch (yield) of half-crenated ark (also called scapharca when exploited as a fishing target in the Azov Sea) was established for the first time, and its exploitation (harvesting)—whether manual, or using hand nets or diving equipment—was permitted; however, its actual catches have not reached the expected volumes. Relevance. Half-crenated ark, due to its high nutritional value, is a promising target species for exploitation, but the manual methods currently permitted for its harvesting are incapable of ensuring its expected catch volumes and meeting recommended goals, which necessitates the introduction of more efficient mechanized fishing gear. The aim of this work is to improve the design of a dredge suitable for harvesting scapharca with the use of small-size vessels. Methods. The standard methods for collecting and processing materials related to the fishing methods, gears, and techniques used in the exploitation of aquatic resources have been employed. Results. A design for the dredge outfitted with a tooth bar and a metal grid collector was proposed, similar to Khizhnyak’s dredge used for veined rapa whelk harvesting. This design ensures its universal applicability for harvesting various mollusc species, providing the option to use netting of different mesh sizes or removable teeth of various shapes. Conclusion. The obtained data will be used in subsequent research and development of techniques for dredge harvesting of scapharca in the Azov Sea, including those involving fishing vessels operating in the open sea.
Keywords: Azov Sea, coastal fishing, fishing gear, half-crenated ark, scapharca, dredges, teeth, inert mass, shell, dredge selectivity, mesh size
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