CONTENT
Biology and Ecology of Aquatic Organisms
Zhivoglyadova L.A., Vekhov D.A., Elfimova N.S., Revkov N.K.
Abstract
Background. The Asian clam Corbicula fluminea (O.F. Müller, 1774) is classified among the most dangerous invasive species in Europe and Russia. In 2017, C. fluminea was discovered in the Lower Don Вasin for the first time. At present, the expansion of the Asian clam in the Lower Don Basin is still ongoing. This conclusion is based on the discovery of a thanatocoenosis of C. fluminea in the Lower- Manych Irrigation System. Relevance. Investigation of the temporary communities of C. fluminea in the irrigation canals will make it possible to assess the role of artificial water bodies in the further expansion of the species. The aim of this work is to characterize C. fluminea beds under the conditions of seasonal operation of irrigation canals based on the data obtained from its thanatocoenosis. Methods. Two days after the water was drained from the irrigation system, aggregations of dead molluscs were recorded—both with bodies still preserved inside the shells and as empty valves. A comprehensive collection of material was carried out at designated sampling plots 1×1 m in size, located in the areas with high concentrations of shells. Results. Presumably, with the start of water supply to the irrigation system (in May), mollusc larvae at the pediveliger stage enter the canals from the main channel of the Don River and actively develop. By autumn, the majority of individuals (80 % of the total number) reach 10–12 mm in size, indicating a high growth rate and favorable conditions within the irrigation system. Some specimens measuring 17–20 mm likely are second- year individuals that overwintered in the the canal section that did not freeze. The average growth rate of the first-year molluscs was 2.8 mm over 30 days, which is comparable to the data for C. fluminea collected in the natural European water bodies. Conclusion. The discovery of C. fluminea in the irrigation system indicates the ability of this mollusc to successfully colonize not only the natural water bodies of the Don River but also artificial canals. These canals apparently create favorable conditions for rapid growth and sexual maturation of the mollusc, promoting its further spread in the region.
Keywords: Asian clam, biological invasion, Bivalvia, alien species
Kalita T.L., Tsarkov M.D., Klimuk A.A.
Abstract
Background. The marine diatom Phaeodactylum tricornutum is characterized by the presence of organic component in the cell skeleton and a balanced biochemical composition. Relevance. These features provide the grounds to consider it a promising feed additive in industrial aquaculture, which motivates the search of the suitable culture media. The aim of this work is to propose an optimal culture medium for growing this species in the context of enrichment culture in artificial environment. Methods. In this work, the growth of enrichment cultures of Ph. tricornutum in the culture media commonly used for their cultivation (Guillard F/2, Conway, von Stosch and Goldberg) has been assessed using direct cell counting in the Goryaev chamber and measuring the optical density at 750 nm with a spectrophotometer. Results. It is shown that the nutrient medium Guillard F/2 is characterized by the optimal ratio of chemical elements (N:P=6, N:Si=3.2 and Si:P=1.8). Conclusion. The combination of this nutrient medium with illumination of 30 μmol·m-2·s-1, photoperiod L:D=16:8 and temperature of 20±2 °C promoted the transition of culture development to the logarithmic growth phase (lasting 9 days) on the 3rd day of the experiment and to the stationary phase on the 17th day. The obtained results can be used in the development of a technology for the industrial production of biologically active substances derived from microalgae.
Keywords: Phaeodactylum tricornutum, cultivation, biotechnology of microalgae cultivation, Guillard F/2, Conway medium, von Stosch, Goldberg medium
Phytoremediation of tannery wastewater using common duckweed (Lemna minor)
Lassana Diop, Stepanenko E.A., Volkova I.V.
Abstract
Background. In the context of ongoing deterioration of aquatic ecosystems due to untreated wastewater discharges—especially from tanneries—there is an urgent need to adopt environmentally friendly treatment methods. Relevance. Traditional methods for treating tannery wastewater are financially and energetically expensive and often unsuitable for developing countries. Phytoremediation offers a promising, cost-effective, and eco-friendly alternative that relies on the use of aquatic plants. The aim of this work is to evaluate the effectiveness of the common duckweed (Lemna minor) in treating tannery wastewater (pre-tanning stage) using a hydroponic system. Methods. The study was conducted under laboratory conditions with five water samples containing different ratios of tannery wastewater diluted with distilled water. Lemna minor was introduced into each aquarium. Analysis of hydrochemical parameters (COD, BOD , NH ⁺, NO -, NO -, suspended solids) was conducted before and after treatment. Results. The sample with 75 % wastewater and 25 % distilled water showed the highest effectiveness: COD reduction by 52.13 %, BOD5 by 77.0 %, NH + by 31.75 %, suspended solids by 80.51 %, and complete removal of nitrates and nitrites. The growth rate of Lemna minor was also the highest in this sample. Conclusion. Common duckweed (Lemna minor) demonstrated strong potential in treating tannery wastewater, proving to be a promising, ecologically safe and low-cost solution. The 75/25 dilution is found to be the most effective.
Keywords: wastewater, tanning, hydrochemical parameters, phytoremediation, COD, BOD5, ammonium, nitrate, nitrite
Pospelova N.V., Priymak A.S., Shiroyan A.G.
Abstract
Background. A comprehensive understanding of the nutritional ecology of bivalves is imperative for elucidating their ecological functions and interactions with their environment. Relevance. Despite the multitude of studies conducted on the subject of nutrition of filter-feeding molluscs, the mechanisms underlying their selective feeding remain to be fully identified. The majority of these studies have been conducted under experimental conditions, while the feeding process of the mussel in its natural habitat has received comparatively less attention. The aim of this work was to evaluate the feeding selectivity of Mediterranean mussel M. galloprovincialis in the Black Sea population in regard to the taxonomic affiliation, shape and size of microalgae cells. Methods. Mollusc and water samples were collected in Artillery Bay (Sevastopol) in 2021. The species composition, abundance and biomass of microalgae in seawater and molluscan stomachs have been determined. The shape and linear dimensions of the microalgae species most frequently occurring in the plankton and mussel food bolus have been analyzed. Results. A total of thirty-four phytoplankton species have been identified in the water, and sixty-two in the mussel stomachs. The similarity of microalgae species in stomach contents and water samples was low (Bray–Curtis Dissimilarity Index ≤0.33). All microalgae species have been divided into three size groups (based on their cell length): 7–57 μm, 58–114 μm, and over 114 μm. The dominant groups in terms of abundance and number of their species have been identified in the phytoplankton composition and molluscan stomach contents. The analysis has revealed that large-celled and colonial diatom algae prevailed in the phytoplankton, while small-celled rounded dinoflagellates and pennate diatoms were dominant in the stomach contents. Conclusion. This study confirms the presence of mechanical selectivity in the feeding process of M. galloprovincialis at the stage of pre-feeding selection based on the size, shape, and type of microalgae cells.
Keywords: bivalve molluscs, microalgae, selectivity, feeding, stomach content, cell size
Status of the Black Sea shrimp (Palaemon adspersus, Palaemon elegans) fishery in the Azov Sea
Saenko E.M., Luzhnyak V.A.
Abstract
Background. In the context of ongoing water salinization and increasing water temperature in the Azov Sea, a decrease in the stocks of anadromous and semi-anadromous fish species has been observed. As a result of the increase in salinity, by 2020, favorable conditions for shrimps had developed in the Azov Sea, which made it possible to include them into the list of major fishing targets. Relevance. These factors necessitate the analysis of fisheries dynamics in the Azov Sea. The aim of this work is to review the status of the shrimp stock and fishery in the context of changing habitat conditions. Methods. This work is based on the statistical data provided by the FSBI “Center for Fisheries Monitoring and Communication” and the Azov-Black Sea Territorial Administration of the Federal Agency for Fisheries, as well as the data collected during expeditionary surveys in 1990–2024. Results. As a result of the conducted research, it has been found that, in the context of increasing salinity levels, the shrimp exploitable stock increased 27-fold from 2015 to 2024. The main commercial aggregations have been recorded in the Northern Azov Region. As compared to 2015, catch volumes have increased by almost 147 times. Realization of the recommended catch was at 79–81 %. The highest gross catch of 160.7–184.0 t was recorded in the Zaporozhye Region, where shrimp fishing operations were carried out in the Obitochny, Berdyansk Bays and the Utlyuk Estuary (Liman); the lowest catch (21.3 t) was in the Donetsk People's Republic. The total body length of shrimp in the catches varied from 2.3 to 5.3 cm. The share of non-commercial size shrimp did not exceed 7 %. Conclusion. In the context of increasing salinity of the Azov Sea waters, a drastic increase in the shrimp commercial stocks up to 3 thousand t has been recorded. With the deterioration of the stocks of traditional fishing targets, an interest in the shrimp harvesting has been observed. This resulted in the unprecedented for the Azov Sea shrimp catch reaching 445 t. Considering the largest catch volumes and the number of fishers actively engaged in fishing operations, the Northern Azov Region experiences the highest fishing pressure. However, given the satisfactory condition of the shrimp stocks, it should be concluded that the commercial potential of these areas has not yet been realized. With the growing interest of fishers in the new fishing targets and expansion of fishing areas, an increase in the catches of commercial invertebrates should be expected.
Keywords: Azov Sea, commercial invertebrates, shrimps, fishery, catches, salinity, distribution, abundance, biomass
Ichthyofauna of Marine and Inland Water Bodies
Korzun Yu.V., Misar N.A.
Abstract
Background. This article presents a simplified method for preparing otoliths of Antarctic toothfish using specialized power tools, combining generally accepted approaches with modified stages of age sample preparation. Relevance. The age determination samples prepared using this method allow for consistent ring identification in the older age groups with the possibility to determine the formation of a nucleus with the next annual ring, which improves the accuracy of the obtained data. The aim of this work is to adapt the general method for age determination using otoliths to the otolith samples of Antarctic toothfish Dissostichus mawsoni, as well as to analyze the data on the length and age composition of the catches obtained by the Russian longline medium fishing trawler “Sparta” in the Ross Sea during the fishing season 2018/2019. Methods. This simplified otolith age determination technique was based on the widely used “break and burn” method, which had been modified in several ways, including grinding the otolith to the center on a grinding wheel and individual calcination of the otolith with a heat gun. Results. A simplified otolith age determination technique for Antarctic toothfish has been tested; it involved modified stages of the sample preparation and the use of modern specialized power tools, which should result in high-quality age preparations. The data on the length and age composition of the toothfish from the сatches in the Ross Sea have been analyzed for the fishing season 2018/2019. The Antarctic toothfish length and age composition has been represented by individuals from 70 to 178 cm in length with a modal value of 135 cm, aged from 5 to 26 years with the age cohort modes of 10, 13 and 15 years. Conclusion. The use of the developed simplified method for preparing age determination samples allows for fairly accurate identification of age rings, including the formation of a nucleus, which impoves the accuracy of the data required for mathematical modeling of fish growth and for stock assessment.
Keywords: Antarctic toothfish, age, otolith nucleus, hyaline and opaque zones, annual ring
Aquaculture and Methods of Artificial Reproduction
Pyatikopova O.V., Bedritskaya I.N., Popov D.A., Sapakhova L.Kh.
Abstract
Background. Cage fish farming in the Astrakhan Region faces a number of problems, among which are a considerable variability of the hydrological regime of its rivers and the increased water heat-up in the summer season. Relevance. Absence of the established hydrological requirements to the cage aquaculture facilities necessitated relevant studies. The aim of this work is to assess the “bottlenecks” of the hydrological regime, which would make it possible to reduce possible risks for cage fish farming at the stage of planning. Methods. Hydrological studies were carried out using generally accepted methods in April, August and November 2024. Such parameters of the aquatic environment as the depth of a watercourse, the velocity of a water current, and the water temperature have been identified. Results. The duration of the period with water temperature over 25.0 °C in the Volga River—the main water body of the region feeding numerous watercourses of the delta—can be about 30 days (according to the data collected by the Astrakhan Central State Hydrometeorological Service), necessitating the decrease in stocking density and/or feeding rates for the aquaculture targets grown in the water bodies of the Astrakhan Region. Results of depth determination with regard to the specifics of the hydrological regime in the investigated area and identified zones of potential shallowing in the water bodies of the Astrakhan Region provide the basis for adjustment of the actual depth values determined during the preliminary studies of the water bodies considered for cage aquaculture towards their increase. Low velocities of a water current observed at some natural water bodies dictate the need for a thorough investigation of watercourses in the process of establishing the sites suitable for cage fish farming. Conclusion. Increased natural temperatures of the water bodies in the Astrakhan Region in summer may be a limiting factor in the cage culture of sturgeon species during this season. The cages used for sturgeon species cultivation require the depth of a water body exceeding 4.0 m (optimally, 5.0 m and more). The water current velocity of 0.1 m/s is the lowest possible for satisfactory operation of cage fish farms in the Astrakhan Region.
Keywords: cage aquaculture, Astrakhan Region, fish farms, hydrological research, water current velocity, water temperature, sturgeons
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