UTTAR PRADESH JOURNAL OF ZOOLOGY

Climate change is increasingly altering freshwater ecosystems and enhancing chemical toxicity in aquaculture environments. The present study investigated the combined effects of climate-related stressors and azoxystrobin exposure on grass carp (Ctenopharyngodon idella). A semi-static experimental design was employed to evaluate behavioural, physiological, haematological, biochemical, and histopathological responses under elevated temperature and reduced dissolved oxygen conditions simulating climate-amplified stress. Exposed fish exhibited behavioural abnormalities including erratic swimming, increased opercular movement, surface gulping, and reduced feeding activity. Significant reductions in oxygen consumption, haemoglobin concentration, erythrocyte count, and haematocrit values were observed, whereas leukocyte counts increased markedly, indicating systemic physiological stress. Biochemical analysis revealed elevated lipid peroxidation and decreased antioxidant enzyme activities, confirming oxidative stress and impaired antioxidant defence mechanisms. Histopathological examination demonstrated tissue damage in the gills, liver, kidney, and intestine. Toxic effects were significantly more severe under combined climate-stress and pesticide exposure conditions than under pesticide exposure alone, indicating that climate change intensifies azoxystrobin toxicity in freshwater fish. The findings suggest that climate-amplified pesticide stress may adversely affect fish health, aquaculture productivity, and freshwater biodiversity. The study highlights the importance of integrating climate-related variables into aquatic toxicological risk assessment and sustainable aquaculture management strategies.