Characteristics of the current state of the ichthiofauna of the lake Kotlovan as a small artificial water body, Dnipro city

Purpose. To investigate the current state of nearshore and pelagic communities of ichthyofauna of an artificial water body: Lake Kotlovan in the city of Dnipro. To develop a set of recommendations and bioreclamation measures to improve and maintain a balanced ecological state of the water body, to increase its recreational value. Methodology.The study of ichthyofauna was carried out in the lake Kotlovan (total area 13.4 hectares), which was artificially created in the late 1960s and 1970s, located in the Industrial District of Dnipro in the area of industrial development. The study was carried out in September 2021 - October 2022 in three main nearshore biotopes of the water body. Ichthyological samples were collected in the nearshore shallow water zone with a small-mesh (fry) seine of 15 meters long with a mesh size of 7 mm in the wings and 3 mm in the codend. Fish selected for further analysis were preserved in a 4.5% formalin solution. Processing and analysis of the collected samples were carried out at the research center “Aquatic Bioresources and Aquaculture” of the Dnipro State Agrarian and Economic University (DSAEU). Generally accepted methods of mathematical analysis were used to process the results. The study was carried out in accordance with the Program for conducting scientific fisheries research of the Scientific Research Center “Aquatic Bioresources and Aquaculture” of the DSAEU for 2022–2026. Findings. The peculiarities of the species composition and distribution of the spontaneously formed ichthyofauna of an artificial water body under the impact of negative factors - discharges of enterprises, communal and household effluents and active recreation - have been established. Ichthyofauna of the lake Kotlovan is impoverished and represented by only 10 species (4 families). The composition of the ichthyofauna lacks bottom-dwelling fish and some littoral species (representatives of the familiesCobitidae, Siluridae, Syngnathidae, Gasterosteidae, Gobiidae), a certain deformation of the taxonomic structure was observed. The absence of individual families of ichthyofauna is an atypical situation for most water bodies in this region. This is due to the artificial development of ichthyofauna and the complex negative effect of the anthropogenic factor and internal trophic relationships. Recommendations on bioreclamation measures for the development of a stable ichthyocenosis with the improvement of the trophic structure and ecological condition of the artificial water body have been developed. Originality. The species composition of the ichthyofauna of an artificially created completely isolated water body in the city of Dnipro, which has existed for about 50 years, was determined for the first time. The current structure of fish groups according to species composition, conservation status, relative abundance, type of feeding and origin were investigated. A high level of the infestation of bleak Alburnus alburnus and silver bream Blicca bjoerkna with ligulosis and perch Perca fluviatilis with eustrongylidosis was observed. Measures and recommendations for improving the state of the ichthyofauna of Lake Kotlovan and increasing the recreational value of the water body were proposed. Practical value. Based on the conducted study, it is possible to evaluate and forecast the future state of the ichthyofauna of small, artificially created and isolated water bodies under anthropogenic pressure. The proposed bioreclamation measures will allow increasing the stability of ichthyocenosis and improving water quality as well as the conditions for recreation of residents, recreational fishing within the boundaries of a large city (a complex of ecosystem services).