CONTENT
Review Articles
The state of the environment of aquatic biological resources, their exploitable stocks, and fishing results in the Azov Sea in 2023–2024 in the context of climate change.
Belousov V.N., Mirzoyan A.V., Bragina T.M., Aleksandrova U.N., Bondarev S.V., Vekhov D.A., Zhukova S.V., Elfimova N.S., Nadolinskiy R.V., Pavlyuk A.V., Pereverzeva M.N., Petrashov V.I., Piatinskii M.M., Saenko E.M.
Abstract
Background. In 2023–2024, the recent trends induced by global climate changes persist in the Azov- Black Sea Fishery Basin—namely, rising water and air temperatures, reduced river water content, and increasing salinity of the Azov Sea. This results in a transformation of the abiotic limiting environmental factors for aquatic biological resources and alters the structure of the stocks exploited by fisheries. Relevance. The ongoing changes in habitat conditions and dominant exploitable species of aquatic biological resources necessitate the introduction of updates and revisions to the existing fishing regulations. To ensure the rational exploitation of natural resources and informationally substantiated decision-making in this area, up-to-date data on the dynamics and composition of exploitable fish stocks, as well as the biological behavior of the respective species, are essential. The aim of this work is to review the results of monitoring surveys examining the habitat and stocks of aquatic biological resources in the Azov Sea and to characterize the impact of the climate change on these resources, their environment, and their exploitation in 2023–2024. Methods. This study is based on archival data and the results of expeditionary monitoring surveys conducted in 2023–2024 in the open waters of the Azov Sea and in Taganrog Bay with the use of light-tonnage vessels and in the coastal waters of the Azov Sea, the Azov estuaries (limans), and sea-flowing rivers with the use of small-capacity fleet (boats). Results. Monitoring of the habitat condition and stock status of the aquatic biological resources of the Azov Sea in 2023–2024 revealed that, despite a certain increase in the water content of the Don River, the continental runoff during this time range remained insufficient for a decrease in the Azov Sea salinity. The artificially regulated hydrograph of the Don River failed to ensure favorable conditions for the spawning of semi-anadromous fish species in floodplain spawning grounds. This study has identified the areas within the Don River and its tributaries that currently play the most crucial role in the reproduction of semi-anadromous fish species. At present, the main spawning sites for zander and roach are located in the Azov limans (estuaries) of the Krasnodar Territory and feeding and rearing facilities of the FSBI “Glavrybvod”. High salinity levels of the Azov Sea do not provide zander and roach with a suitable feeding environment across most of its area. Reclamation of the Azov Sea as an internal Russian water body allowed for an expansion of the artificial reproduction of sturgeon fish species, which resulted in the positive trend in their stock abundance. In 2024, the total biomass of the Russian sturgeon stock exceeded 3 thousand tons. The biomass of gelatinous organisms in the Azov Sea in 2023–2024 reached 4–6 million tons. Due to competition with gelatinous plankton, recruitment into the spawning populations of the pelagic fish species was characterized by low-yield generations, despite moderate average monthly relative densities of fodder zooplankton during the summer season. Changes in the hydrological conditions are reshaping the exploitable stocks supporting the Azov Sea fisheries. The share of semi-anadromous species, gobies and planktivorous fish species in the total Azov Sea catch declined from 80 to 25–30 %, while the share of invertebrates increased by 5 times and, with that of Black Sea turbot and so-iuy mullet, exceeded 60 %. Changes in the composition of the Azov Sea biocoenoses have led to a gradual restructuring and realignment of fisheries, marked by increasing catches of invertebrates, Black Sea turbot, and so-iuy mullet. Conclusion. The trend towards a reduction in the river runoff and a gradual increase in the salinity of the Azov Sea is expected to persist in the short term. As a result, the conditions for reproduction of all semi-anadromous species will be unfavorable, while trends in the reproduction efficiency among marine fish species are going to vary (a decrease is anticipated for pelagic species and gobies, whereas so-iuy mullet and Black Sea turbot are projected to show an increase). At the same time, a high abundance of gelatinous organisms and an increase in abundance of molluscs are expected. In the context of increasing efficiency of artificial reproduction, the population of the Russian sturgeon is expected to grow.
Keywords: Azov Sea, climate changes, salinity, natural and artificial reproduction, stock assessment, Russian sturgeon, fodder zooplankton, limans (estuaries), semi-anadromous fishes, commercial invertebrates
Environmental Concerns and the State of Aquatic Environment
Results of monitoring the content of priority toxicants and the hydrochemical status of the Don River in the area near stanitsa Kochetovskaya (Rostov Region) in May 2025.
Kosenko Yu.V., Bragina T.M., Shevtsova E.A.
Abstract
Background. Under the influence of anthropogenic economic activity, the Lower Don region, including the area near stanitsa Kochetovskaya, has undergone a significant transformation as a natural ecosystem. Relevance. The assessment of the water quality of the Don River as a habitat for aquatic bioresources currently remains highly relevant. The inflow of water to the large Don Sturgeon Hatchery through a water intake in the investigated area contributes to the special importance of monitoring the water quality in this region. The aim of this work is to analyze the hydrochemical parameters and the content of priority toxicants in the water and bottom sediments of the Don River near stanitsa Kochetovskaya, Rostov Region, upstream from the Kochetovsky Hydrotechnical System (sampling point 2) in the late spring of 2025. This article continues a series of publications presenting the results of environmental monitoring of the habitat of aquatic bioresources in the Lower Don region. Methods. Standard sampling methods were employed to collect water and bottom sediment samples for further determination of their chemical parameters. Chemical analyses of water and bottom sediments were carried out in accordance with the methods approved at the federal level. Results. In the water of the investigated area, the dissolved oxygen content was 6.1 mg/dm3, while ammonium and nitrate nitrogen concentrations were 0.050 and 0.202 mg/dm3; total water mineralization (total dissolved solids) was 780 mg/dm3, and the water was characterized as eutrophic (17 units) in terms of its trophic level. The total content of petroleum products in water and bottom sediments was low. Anionic synthetic surfactants, organochlorine pesticides, and polychlorinated biphenyls were not detected in water and bottom sediments in the investigated area. Exceedances of MACfishery in water were recorded for copper (3.3 μg/dm3) and manganese (17 μg/dm3); their concentrations, however, did not reach the levels critical for aquatic bioresources. The content of heavy metals in bottom sediments corresponded to average long-term values. Conclusion. The living environment of aquatic biological resources in the Don River in the area near stanitsa Kochetovskaya was favorable for their growth and development.
Keywords: Don River, lower reaches, Rostov Region, hydrochemical parameters, priority toxicants, chemical analysis
Biology and Ecology of Aquatic Organisms
Syrton (drifting benthos) of the riparian zone of the Poronay River (Sakhalin Island) in the autumn period
Zhivoglyadova L.A., Labay V.S., Zavarzin D.S., Shpilko T.S.
Abstract
Background. The study of benthic invertebrate migrations in the water column is particularly important in Far Eastern rivers, where zooplankton development is limited and syrton constitutes one of the primary food sources for fish. Relevance. On Sakhalin Island, the drift of aquatic invertebrates has been studied mainly in small rivers, while the syrton of the Poronay River—the island's largest watercourse—has remained virtually unstudied to date. The aim of this study was to assess the quantitative characteristics of syrton and to analyze the daily dynamics of aquatic invertebrate drift across different sections of the longitudinal profile of the Poronay River. Methods. The study was conducted in 2004–2006 in the autumn period. Samples were collected at six stations, at each of which a daily series of counts was carried out. As a rule, sampling was conducted hourly in the time range from 21:00 to 7:00 and every 4 hours during the remainder of the day. The trap (entrance opening 30×40 сm, gauze netting No. 23) was installed at a single site in the riparian zone at a depth of 0.4 m. Results. The average daily abundance of syrton ranged from 0.025 to 1.490 ind./m3, while the biomass varied from 0.074 to 4.500 mg/m3. In all sections except the clay channel, aquatic invertebrate drift showed a pronounced diel rhythm, with major activity peaks at dusk and during the night. Conclusion. The obtained data contribute to a better understanding of the structure and functioning of the Poronay River communities and allow for a more comprehensive assessment of the role of syrton in the river's trophic system.
Keywords: drift of aquatic invertebrates, daily dynamics, food supply of fish, rivers of Sakhalin Island
Seasonal cycle and features of spatial distribution of chlorophyll α concentration in the Azov Sea based on OLCI images for 2016–2024
Kulygin V.V., Dashkevich L.V., Berdnikov S.V., Shirokov S.V.
Abstract
Background. For over 15 years, the Azov Sea ecosystem has been experiencing significant changes in its hydrological regime—increasing salinity and water temperature, which affects all components of the sea's ecosystem (from plankton to fish communities). Relevance. To understand the sea's current state and identify ongoing changes, it is necessary to rely on a system of ecosystem indicators. Chlorophyll α concentration is a widely accepted quantitative parameter of phytoplankton biomass and can serve as an indicator of production processes, information on which can be obtained with high spatial and temporal resolution based on satellite ocean color data. The aim of this work is to identify the spatiotemporal features of the distribution of chlorophyll α concentrations in the Azov Sea for the time range 2016–2024 based on OLCI images. Methods. Chlorophyll α concentrations were calculated based on OLCI satellite images with the use of regional models. Spatiotemporal aggregation was performed, and variations in chlorophyll α concentrations were analyzed across various areas of the Azov Sea. Results. Seasonal and interannual variation patterns in chlorophyll α concentrations were identified across various areas of the Azov Sea. Long-term change trends were calculated, and their statistical significance was assessed. Conclusion. Seasonal variation patterns in chlorophyll α concentrations in Taganrog Bay and the open part of the Azov Sea differ considerably. Between 2016 and 2024, a downward trend in chlorophyll α concentrations was observed in the western and central regions of Taganrog Bay.
Keywords: chlorophyll α, Azov Sea, OLCI, remote sensing
Macrozoobenthos of loose pebble substrates in the coastal part of Laspi Bay (Black Sea, Crimea) in 2016.
Makarov M.V., Kovaleva M.A., Kopiy V.G.
Abstract
Background. Coastal biotopes are subjected to intense terrestrial anthropogenic pressure; it is also true for Laspi Bay, where numerous recreational and industrial facilities are located along the shoreline. Relevance. Most benthic surveys in the coastal zone were conducted either at greater depths or a long time ago, which necessitated the examination of benthos in this area. The aim of this study is to analyze the data on the species composition, abundance, biomass, occurrence, and trophic affiliation of benthic macrofauna in the coastal area (depths 0–9 m) of Laspi Bay in the summer of 2016. Methods. Sampling was carried out according to the generally accepted benthic methodology. Results. In 40 samples taken at 20 stations, 73 species belonging to the phyla Annelida (22 species), Mollusca (23 species), Arthropoda (24 species), Chordata (1 species) were recorded. Representatives of Nemertea, Oligochaeta, and Platyhelminthes, which were not identified to the species, appeared in the calculations as one species each. The average abundance was 1723±22 ind./m2, and the average biomass was 11.199±0.209 g/m2. Species Saccocirrus papillocercus Bobretzky, 1872 (516 ind./m2) prevailed in terms of abundance, while Chamelea gallina (Linnaeus, 1758) (5.292 g/m2) prevailed in terms of biomass. Based on the Functional Abundance Index, a community of the polychaete Saccocirrus papillocercus at the depth of 0 m, a community of the bivalve mollusc Chamelea gallina at the depths of 0.5–3.5 m, a community of the bivalve mollusc Donax semistriatus at the depths of 5.0–6.5 m, and a community of the gastropod Bittium reticulatum at the depth of 9 m were identified. In terms of occurrence (70 %), Bittium reticulatum was the most dominant species. Conclusion. In terms of trophic affiliation, the identified macrozoobenthos included phytophages, detritophages, seston feeders, сarnivorous species (ectoparasites, scavengers and predators), polyphages, as well as species with an unidentified trophic range. In terms of species number, polyphages prevailed, while seston feeders prevailed in terms of biomass.
Keywords: benthos, Laspi Bay, Black Sea, species, abundance, biomass, occurrence, community, trophic affiliation
Phytoplankton dynamics in Golubaya (Blue) Bay (Gelendzhik) in 2024
Fedorov A.V., Fedorova P.A., Khomenko S.A., Klyuchantseva A.P.
Abstract
Background. Phytoplankton is the most important link in the biological carbon pump, and the seasonal changes of its species composition are accompanied by a transition between organic and carbonate pumps. Relevance. The increasing concentrations of carbon dioxide in the atmosphere and overall climate warming have led to the growing interest in investigating possible natural mechanisms for its removal from the cycle, particularly through absorption by the World Ocean. Understanding the functioning of the carbon pump in the Black Sea requires systematic, long-term data on seasonal succession and the dynamics of quantitative characteristics of phytoplankton. The aim of this work is to verify the correspondence of the dynamics of phytoplankton in Golubaya (Blue) Bay to the model scheme of seasonal succession obtained earlier: small diatoms (early spring) → coccolithophorids (late spring and early summer) → large diatoms (summer). Methods. Sampling was conducted near the pier of the Southern Branch of the P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences. Fixation and concentration of samples, as well as counting and identification of cells, were performed according to standard methodologies. Results. A brief local bloom of Skeletonema costatum in mid-February was followed by a mixed community of coccolithophorids and small diatoms in March and April, with a predominance of the genus Pseudo-nitzschia. In late May and June, increased abundance and biomass were characteristic of a diatom community with diverse species composition. The abundance of Emiliania huxleyi in 2024 barely exceeded 1 million cells/L, which is lower than in previous years. In July, Pseudosolenia calcar-avis prevailed and reached a maximum biomass of 3069.2 mg/m3 (83 % of the total), which caused the appearance of sea snow in August. Conclusion. In 2024, the phytoplankton dynamics in Golubaya (Blue) Bay generally followed the pattern: small diatoms (early spring) → coccolithophorids (late spring and early summer) → large diatoms (summer), yet exhibited certain pecularities.
Keywords: phytoplankton, seasonal dynamics, diatoms, coccolithophorids, Black Sea
Ichthyofauna of Marine and Inland Water Bodies
Dynamics of abundance and biomass of the exploitable part of the tugun Coregonus tugun (Pallas, 1814) population in the Yenisei River
Yablokov N.O.
Fisheries and Processing of Aquatic Bioresources
Biological safety of fresh and frozen fish sold in the retail network of Krasnodar
Strelkova O.V., Ivanenko A.M.
Informational Messages
Decapods (Decapoda Latreille, 1802) of the Black Sea near Cape Opuk, Crimean Peninsula
Kulish A.V., Kibenko V.A., Moiseenko O.I., Adzhiumerov A.E.
A bright legacy in science (dedicated to the 90th anniversary of the birth of Valentina Georgievna Dubinina)
Zhukova S.V.