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Ribogospod. nauka Ukr., 2025; 4(74): 105-128
DOI: https://doi.org/10.61976/fsu2025.04.105
UDC 574.5+556.53(477.63)

Transformation of the hydrological regime of the middle reach of the Bazavluk River and its impact on its fish population

D. Kobyakov, This email address is being protected from spambots. You need JavaScript enabled to view it. , ORCID ID 0000-0002-7086-8337, Dnipro State Agrarian and Economic University, Dnipro
R. Novitskyi, This email address is being protected from spambots. You need JavaScript enabled to view it. , ORCID ID 0000-0001-9373-5759, Dnipro State Agrarian and Economic University, Dnipro

Purpose. To investigate the current state of hydrological transformations, biotope dynamics and changes in the species composition of fish in the middle reaches of the Bazavluk River, to identify factors determining the loss of habitats for globally protected fish species.

Methodology. The study was conducted in the summer of 2024–2025 in the middle reach of the Bazavluk River. Comprehensive methods of material collection were used and surveys of recreational fishermen were conducted. The conservation status of the species was determined, and all fish after identification were released alive to the watercourse. Remote sensing methods of the Earth were applied using open satellite data Sentinel-2 (ESA). The images were processed in QGIS 3.28 to generate thematic vegetation cover maps.

Findings. Fragments of natural biotopes have been preserved on the Bazavluk River but the river ecosystem has undergone significant changes under the pressure of various factors. The consequences of this are the degradation of floodplain and riverbed biotopes, increased eutrophication and siltation processes, and reduced flow rates. The current state of the river ecosystem is unsustainable. The ichthyofauna of the middle reach of the Bazavluk River in 2024–2025 included 21 fish species (7 families) with Cyprinidae dominating (a typical structure for floodplain rivers of the Dniprо basin). There is a tendency towards simplification of the species composition and a decrease in the proportion of rheophiles. Seven species with conservation status were noted: C. carassius, L. idus, Rh. amarus, C. taenia, L. delineatus, P. platygaster, N. fluviatilis. Their presence testifies to the preservation of residual natural habitats but at the same time indicates the high ecological vulnerability of populations sensitive to transformations, which is reliably shown by GIS analysis of the dynamics of the areas of the main biotopes of the river. In 2015–2025, the area of ​​open water surface decreased by 12.8%, while the area of ​​wetland vegetation communities increased by 240%. The current state of the ichthyofauna of the Bazavluk River as a natural core of the eco-network is characterized by a high level of ecological vulnerability and signs of habitat degradation.

Originality. For the first time, data on the current state of hydrological transformations, biotope dynamics and changes in the species composition of fish in the middle reaches of the Bazavluk River have been systematised.

Practical Value. The results obtained are of scientific and practical importance for the development of regional programmes for monitoring small rivers in the steppe zone of Ukraine, for justifying measures for biological control measures and ecological reconstruction of degraded aquatic ecosystems.

Keywords: Ukraine, Dnipropetrovsk region, Bazavluk River, Emerald Network, hydroecosystem transformation, aquatic bioresources, ichthyofauna.

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