Pathological changes in the gills of common roach (Rutilus rutilus Linnaeus, 1758) from the Konoplyanka River of the city of Kam’ianske

Purpose. To conduct a comprehensive analysis of the impact of anthropogenic pollution on common roach (Rutilus rutilus) caught in the Konoplyanka River. To study pathological changes in fish gills as an indicator of water quality and to determine the activity of the biochemical marker - glutathione-S-transferase (GST). Methodology. Material for the study was obtained during 2022–2024 in the Konoplyanka River within 4 sampling sites with varying degrees of anthropogenic load. The object of the study was age-1+ common roach. Histological studies were performed according to generally accepted methods. Gills were obtained by anatomical dissection from freshly caught fish. Determination of glutathione-S-transferase activity by spectrophotometric analysis. The content of heavy metals in fish carcasses was determined by atomic absorption spectrophotometry. The obtained data were processed statistically to confirm the significance of the obtained results. Findings. The analysis showed that fish from all studied sampling sites of the Konoplyanka River exhibited significant pathological changes in their gills. The most common were: curvature and fusion of lamellae, hyperplasia and desquamation of the respiratory epithelium. These damages were most pronounced in fish at sites where, according to previous studies, high levels of heavy metals and radionuclides were recorded. It was found that the fish caught in the upper part of the river had a significantly higher copper content compared to fish from other sites by 2.8–2.0 times. Glutathione-S-transferase activity was significantly reduced in contaminated areas, indicating depletion of the fish’s defence mechanisms under the effect of toxic stress. Originality. For the first time, a comprehensive study of histological and biochemical markers about conditions of the common roach from the Konoplyanka River was conducted under the effect of technogenic impact of the industrial zone of the metallurgical and chemical industry. Practical Value. The feasibility of using such an integrated approach for monitoring aquatic ecosystems. The data obtained can be used to assess the ecological state of the Konoplyanka River water areas and develop effective measures to protect water resources from anthropogenic impact. This is especially true for small rivers, which are often overlooked in monitoring programs. Keywords: anthropogenic pollution, biomarkers, histopathology, glutathione-S-transferase (GST), heavy metals, tailings ponds.