IMPACT OF POLLUTANTS ON THE GILL APPARATUS OF FISH IN THE ILI-BALKHASH BASIN

The article was written as part of the Ministry of Science and Higher Education of the Republic of Kazakhstan’s project AP 23486220, titled “Study of the important organ systems reactivity in the main commercial fish species of the Ile-Balkhash basin under anthropogenic load.” (2024-2026). The ecological condition of the Ili-Balkhash Basin raises serious concerns due to increasing anthropogenic pressure, accompanied by the influx of heavy metals, pesticides, and other organic pollutants into water bodies. Fish gills, as a highly sensitive organ of external respiration, serve as a reliable bioindicator of water toxicity. As part of this study, morphological and histological analyses of the gill apparatus were conducted on three commercially important fish species – Cyprinus carpio, Abramis brama, and Sander lucioperca — caught in different areas of the Ili-Balkhash Basin. In fish inhabiting zones with elevated pollutant concentrations, pronounced pathological changes in gill tissue were observed, including epithelial hyperplasia, lamellar fusion, destruction of the capillary network, and inflammatory infiltration. The severity of these alterations correlated with the level of aquatic pollution. Cyprinus carpio demonstrated the highest sensitivity to pollutants, whereas Sander lucioperca showed relative resistance. The findings indicate a significant impact of waterborne pollutants on the morphofunctional condition of the gill apparatus, and consequently, on the viability and productivity of fish populations. These results highlight the urgent need for regular ecological monitoring and the implementation of protective measures to preserve the aquatic ecosystem of the Ili-Balkhash Basin, safeguard biodiversity, and ensure sustainable fisheries. Keywords: Ili-Balkhash Basin, aquatic pollutants, gill pathologies, Cyprinus carpio, Abramis brama, Sander lucioperca, histomorphology.