Аңдатпа
Abstract In recent decades, there has been an increase in the pollution of the waters of the Ile-Balkhash basin by agricultural, industrial and domestic discharges, which has negative consequences for the ichthyofauna. The aim of this study was a histopathological analysis of the condition of the gills, which are the most sensitive to contamination of fish organs, due to their direct and constant contact with water. 7 specimens of three main fish species of commercial fish fauna were caught: bream (Abramis brama) and carp (Cyprinus carpio), both as typical benthophages with some specific feeding features and pike perch (Sander lucioperca). Microscopic analysis of the gills of the common bream (Abramis brama) revealed epithelial hypertrophy and hyperplasia, mucosal and chloride cell changes, epithelial detachment, necrosis, hyperemia, and aneurysms, which were quantified using a semi-quantitative approach. It was found that epithelial hypertrophy, hyperplasia, epithelial detachment and necrosis significantly varied between seasons, while the severity of necrosis was significantly higher in one of the seasons. Comparative analysis showed that in the carp (Cyprinus carpio), adaptive changes in the gills predominate, while in the pike perch (Sander lucioperca), as a more sensitive species, pronounced destructive lesions indicate a high level of environmental stress. Discriminant canonical analysis confirmed that epithelial hyperplasia, mucosal cell changes, epithelial detachment and necrosis are the main factors of seasonal differentiation. The results obtained demonstrate the high informative value of histopathological biomarkers of fish gills for assessing the seasonal dynamics of water quality within a single aquatic ecosystem.