Recent Submissions

  • Black Sea–Caspian sprat (tyulka) industrial fishing in the Azov Sea: Presently used fisning gear, methods, and its current trends

    Stafikopulo, Aleksei; Vtyurina, N.V.; Gorbatyuk, Ya.I. (2023)
    Водные биоресурсы и среда обитания
    This paper presents the main fishing methods and gears previously used or appraised and currently applied in the course of Black Sea–Caspian sprat (tyulka) fishing in the Azov Sea: their performance, merits and demerits. Black Sea–Caspian sprat (tyulka) fishing comprises the coastal fishing with pound nets and the fishing off the board of fishing vessels with purse seines ans midwater trawls. Recently, sprat catches with pound nets have been on the decline; meanwhile, use of fishing vessels, albeit more resource-consuming and dependent on the multitude of factors, can prospectively be more productive than the coastal fishing, even though currently it shows lower catches. A brief characterization of the Black Sea–Caspian sprat (tyulka) industrial fishing in the recent years is given, its trends and challenges are discussed. Daily vessel reports have been processed for 2015–2021, and the comparative data on the operation of the vessels of various types are presented; the trends in the changing industrial fishing parameters during the investigated period show a considerable decrease in all the parameters. Another crucial issue is the necessity to reduce the by-catch of non-target fish species (sturgeons, Black Sea turbot) in long-continued depressed state with midwater trawls. The presented data will allow for the current status assessment of the Black Sea–Caspian sprat (tyulka) industrial fishing and envisioning the efficient, yet selective and environmentally sound fishing methods to be developed and revised.
  • Catch composition of the European anchovy (Engraulis encrasicolus L., 1758), wintering off the coast of Abkhazia in the 2021/2022 fishing season

    Dbar, Roman; Gamakhariya, Paata (2023)
    Водные биоресурсы и среда обитания
    Based on the available data for the 2021/2022 fishing season, the ecological structure and fishing biological parameters of the European anchovy (E. encrasicolus L., 1758), wintering in the coastal waters of Abkhazia, have been analyzed. This paper presents materials that make it possible to analyze the dynamic parameters of the Azov and Black Sea stocks of the European anchovy aggregating off the coast of Abkhazia in the winter season. A comparative analysis of the main biometric parameters has been carried out. For data analysis, well-established ichthyological methods have been used. The available data on the European anchovy (both Black Sea and Azov Sea forms) caught during the investigated period characterize the dynamics of the length–age catch composition and are indicative of its intra-annual fishing patterns. Changes in the population characteristics present in the catch composition as compared with the previous years have been identified. The absolute catch values and their fluctuations are presented by the month. Analysis of the available material has indicated the main dynamic changes that characterize the wintering anchovy population as stable with a tendency for its total biomass development on a moderate level, which is not conducive for increasing the fishing effort in the next 1–2 years.
  • Transformation of the polychaete taxocene in the shallow part of Karkinit Bay under conditions of changing salinity

    Podzorova, Darina; Boltacheva, Natalia (2023)
    Водные биоресурсы и среда обитания
    Karkinit Bay is the largest bay of the Black Sea. Since the 1960s, after the construction of the North Crimean Canal, the water in the top of the bay was heavily desalinated by runoff from fish ponds and irrigation systems. In 2014, after the canal was blocked, the salinity of the water increased, and the living conditions of the organisms changed. This work is aimed at the assessment of the change in the species composition and quantitative characteristics of the polychaete taxocene in the shallow zone of Karkinit Bay in 2018, which resulted from the changes in water salinity, as compared to those in 2008. The studies were carried out in August of 2008 and 2018—in three sampling areas at 17 stations (in 2008 and 2018 alike) at depths of 0.2–1.7 m. Samples of macrozoobenthos were collected using a manual bottom grab with a sample area of 0.04 m2. In the top part of Karkinit Bay in the first half of the 21st century, 35 species of polychaetes were recorded. Polychaete worms belonging to 19 families have been identified, with the families Phyllodocidae, Syllidae, Nereidae, and Spionidae comprising the largest number of species (4 species each). Three species — Lysidice unicornis, Polyophthalmus pictus, Syllis prolifera — were recorded in Karkinit Bay for the first time. It is shown that, with the post-2014 increase in salinity, the species richness of the polychaete taxocene in the investigated area has also increased. In 2008, 24 species were found, and in 2018, 32 species. The average abundance of polychaetes in 2008 was 948± 345 ind./m2, and in 2018, it was 417±161 ind./m2. Hediste diversicolor reached the highest abundance in 2008 (average abundance 676±371 ind./m2, maximum abundance 2313 ind./m2). In 2018, Polydora cornuta (600 ind./m2), Platynereis dumerilii (225 ind./m2), and Scolelepis tridentata (450 ind./m2) were characterized by the highest abundance. With an increase in salinity in the range of 1.5–17.8 ‰, a decrease in the density of H. diversicolor was recorded and, conversely, an increase in the density of other Polychaeta species.
  • Evaluation of the tolerance threshold of marine benthic diatom Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 (Bacillariophyta) under the impact of copper (II) ions

    Nevrova, Elena; Petrov, Alexei (2023)
    Водные биоресурсы и среда обитания
    Copper compounds accumulate in marine bottom sediments as the result of human activity and, being highly toxic, affect microphytobenthos. Evaluation of the tolerance ranges of benthic diatoms to copper pollution is important for biotesting and assessment of coastal marine environment. This work is aimed to reveal the dynamics of growth and cell death of marine benthic diatom Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 under the impact of a wide range of copper (II) ions concentrations over the course of a 10-day experiment in clonal culture, as well as to identify a tolerance threshold for this species, critical for its survival when exposed to the toxicant. The study has focused on assessment of the changes in the proportion (%) of alive cells, absolute cell number and specific growth rate of the culture at different exposure durations and concentrations of Cu2+ ions (32–1024 μg/L) and was meant to evaluate the applicability of this species as a new test object for ecotoxicology. In the control culture and in the cultures exposed to Cu2+ in the range of concentrations 32–256 μg/L, the proportion of alive cells did not change over the course of the experiment (95–99 %). At Cu2+ concentration 320 μg/L, the proportion of alive cells decreased to 23 % on the 3rd day and to 10 % on the 5th day, which provided a basis to consider this value as a threshold one for P. aestuarii survival. At Cu2+ concentrations 384 μg/L and higher, up to the maximum one (1024 μg/L), drastic inhibition of the culture was recorded as early as on the 1st day, and on the days 3–5, all the cells died. The increase in the absolute cell number in the concentration range 32–256 μg/L was consistent with the dose–response sigmoid model. Over the timespan of days 1–7, the cell number increased by 3–5 times, reaching its maximum, and then it decreased by 10–12 % by the 10th day. At Cu2+ concentrations 320 μg/L and higher, the increase in the cell number was strongly suppressed since the 1st day. Within the 32–256 μg/L range, the test culture is characterized by positive specific cell growth rate for the period up to 7 days; at the threshold concentration 320 µg/L and higher, this test parameter becomes negative. Thus, P. aestuarii should be recommended as a new appropriate test object both for toxicological experiments and for monitoring of coastal marine environment affected by technogenic pollution.
  • Polychaeta taxocene in the coastal area of Lake Donuzlav

    Kopiy, Vera (2023)
    Водные биоресурсы и среда обитания
    This work is based on the data collected during the benthic survey of soft sediments in the coastal area of Lake Donuzlav conducted in August, 2020. The current status of the species composition of polychaetes in Lake Donuzlav was investigated. The samples were collected using a manually operated grab sampler with a capture area of 0.04 m2 at the depths from 1 to 8 m. The following indicators were used to describe the quantitative development of benthos: abundance, biomass, occurrence, density index, and Czekanowski–Sørensen index. A total of 31 species of polychaetes have been found. The average values of polychaetes abundance and biomass in the investigated area were 239±51 ind./m2 and 1.537±0.599 g/m2, respectively. The main contribution to the total abundance is made by Spio decorata, and to the total biomass by Lagis neapolitana. The largest number of species and the highest abundance were recorded at the depths of 1.1–2 m. The largest biomass was recorded at the depths of 6.1–7 m. The ranked series according to the density index is headed by L. neapolitana, Glycera tridactyla, and S. decorata. The trophic structure of polychaetes is represented by poly-, phyto-, detritophages, carnivores, and the animals, the food spectrum of which has not been studied. The most widely represented group is carnivores; it comprises 10 species of polychaetes. The least number of species (1) was recorded for phytophages. Over 1990–2020, 73 species of polychaetes were identified; they belonged to 29 families and 56 genera.
  • Specific features of spatial distribution of hydrochemical parameters in the Curonian Lagoon of the Baltic Sea in 2018–2022

    Stashko, A.V.; Aleksandrov, S.V. (2023)
    Водные биоресурсы и среда обитания
    Curonian Bay of the Baltic Sea is a lagoon that is considered to be a water body of the highest fisheries importance. Its current geoenvironmental status is characterized by a number of problems: influx of biogenic substances from a large catchment area, algal bloom, etc. As part of the monitoring surveys of the habitat of aquatic living resources that were conducted in Russian waters of Curonian Lagoon in 2018–2022, the spatial distribution of hydrochemical parameters was investigated in 6 areas established on the basis of their morphometric and hydrological features: Teply (Warm) Bay, western, central, eastern, and southern areas, and the Neman River discharge zone. Hydrochemical conditions in Teply Bay were characterized by a considerable deviation of dissolved oxygen concentrations from the rest of Russian waters of Curonian Lagoon, as well as by the higher values of BOD5 and ammonia nitrogen, and lower values of pH and nitrate nitrogen. In the western area, the lowest content of dissolved oxygen, BOD5, ammonia, and nitrate nitrogen was recorded. In the southern area, there was a reduced content of ammonia nitrogen and nitrate nitrogen. In the central area, the values of hydrochemical parameters were close to the average ones for Russian waters. The eastern and Neman River discharge areas, exposed to significant influence of the Neman River runoff, were characterized by a high concentration of nitrate nitrogen during seasonal flood, as well as by increased values of ammonia nitrogen and BOD5 during algal bloom in summer.
  • The influence of water salinity on generation of near-bottom hypoxic phenomena and the level of primary production of organic matter in Taganrog Bay

    Kosenko, Yu.V.; Baskakova, T.E.; Zhukova, S.V.; Barabashin, Timofey; Piatinskii, Mikhail (2023)
    Водные биоресурсы и среда обитания
    At present, the Azov Sea ecosystem exists in the context of continuously decreasing continental runoff and increasing water salinity, which reached in 2020–2021 the highest values for the entire period of observations since 1962. The increase in water salinity inevitably leads to the transformation in the composition of biological communities, which has a pronounced effect on the environment and fisheries. This paper discusses the long-term impact of water salinity on the development of near-bottom hypoxic phenomena and on the volume of primary production of organic matter by phytoplankton in Taganrog Bay during the summer season (1962–2021). A statistical ecosystem analysis describing the contribution of the major hydrological and hydrochemical factors into the processes of hypoxia formation in the bottom water layer of Taganrog Bay has been performed. It is shown that the desalinization of the waters of Taganrog Bay in 1993–2008 was accompanied by the increase in the size of hypoxic zones in the bottom water layer. During the modern period of salinization extending from 2009 to the present, there has been recorded a decrease in the scale of oxygen deficiency in Taganrog Bay. The most crucial contribution to the hypoxic processes in Taganrog Bay is provided by the stability of water masses, water temperature, organic nitrogen concentration, and the water salinity (due to the effect of salinity on the stability of water masses). During the streaks of Taganrog Bay salinization, the decrease in the stability of water masses and in the content of organic nitrogen and phosphorus in the water (crucial factors in the formation of hypoxic zones) has been recorded. The highest rates of the primary production of organic matter by phytoplankton in Taganrog Bay were observed during the desalinization period of 1962–1968, and the lowest ones were recorded during the salinization periods. The results of this assessment have exposed the significant relationship: the primary production of organic matter depends on the average annual runoff of the Don River, the water salinity, and the concentration of mineral nitrogen.
  • Assessment of the physicochemical properties of the main rivers of the Mekong Delta and their ecological zoning

    Karpova, Evgeniia; Nguyen, Dinh Cu; Statkevich, Svetlana; Ba Hai, Truong; Chesnokova, Irina; Kurshakov, Sergei; Аблязов, Эрнес; Slynko, Elena; Duong, Thi Kim Chi (2023)
    Водные биоресурсы и среда обитания
    The Mekong Delta is one of Asia's largest megadeltas. It is a region with unique biodiversity and the main food source for a large part of the population of Vietnam and Cambodia. The decrease in the biodiversity and resource capacity of the delta, associated with the growth of anthropogenic impact and other negative environmental factors, requires effort to maintain its ecosystem in a state favorable for the life of aquatic organisms, for which the first step is to organize effective monitoring of aquatic communities. Its organization must consider the complex structure of the delta and related features of the physicochemical characteristics of the habitat. The mean and interval values of the parameters were as follows: transparency was 47.7±16.4 (10–100) cm; in the surface water layer, the temperature was 29.7±1.37 (26.0–33.3) °C, electrical conductivity was 5490.4±8392.5 (133–33623) µS/cm, total dissolved solids were 3556.2±5445.8 (86.5–21853), pH was 7.6±0.3 (6.9–8.4), and dissolved oxygen was 4.8±1.05 (3.0–8.9) mg/L; in the bottom water layer, the temperature was 29.6±1.43 (26.0–34.1) °C, electrical conductivity was 7671.4±11193.2 (125–37870) µS/cm, total dissolved solids were 4905.3±7199.8 (78.0–24615.5), pH was 7.6±0.3 (6.9–8.2), and dissolved oxygen was 4.6±1.00 (2.6–7.7) mg/L. The zoning of the delta based on the knowledge of the environment makes it possible to organize the monitoring process in the most rational way. Following the results of the analysis of physicochemical parameters, the boundaries of zones with different environmental conditions that affect the formation of fish communities have been determined. The main contributing factors are salinity (3 zones), oxygen regime (3 zones), and runoff distribution (4 zones). The interrelation between the delta zoning according to the hydrochemical regime and the structural features of the fish communities at the family level has been found, which further supports the idea that such zoning must be taken into consideration when organizing monitoring surveys.
  • The effect of Cayunis, EC fungicide on various links of the trophic chain in a model experiment

    Zinchuk, O.A.; Baimova, I.B.; Karpushova, T.N.; Besschetnova, L.M. (2023)
    Водные биоресурсы и среда обитания
    Currently, there is an ongoing process of development of the next-generation pesticides, which use for the purposes of agriculture has negative implications for the environment. Their hazard potential is attributable to two factors: high biological activity and their application method involving their dispersion in the environment. It necessitates the investigation of the effect of pesticides on aquatic organisms, which includes changes in their habitat, disruptions of their vital functions, especially at the early stages of their ontogeny, accumulation in their tissues, and movement along the trophic chain. Toxicological assessment of the fungicide Cayunis, EC effect has been conducted on the aquatic organisms of various taxonomic groups: microalgae (Scenedesmus guadricauda (Turpin) Brébisson, 1835), macrophytes (Elodea canadensis Michaux, 1803), molluscs (Planorbarius corneus (Linnaeus, 1758)), embryos and fry of the round goby (Neogobius melanostomus (Pallas, 1814)). Over the course of the experiment, the conditions for intoxication were identified, and the toxicometric characteristics of the aquatic organisms belonging to various trophic levels were estimated. Using an experimental approach, the threshold and no observed effect concentrations of the preparative form of Cayunis, EC pesticide have been identified for each test subject. This study made it possible to compare the sensitivity of each investigated test subject to the fungicide. Among the studied test subjects, round goby fry has proved to be the most sensitive to the effect of Cayunis, EC fungicide.