Asian Journal of Research in Biology

Freshwater ecosystems of the Ambikapur region of Surguja district, Chhattisgarh, India, are increasingly subject to pH perturbation arising from coal mining, agricultural runoff, and industrial and municipal discharge. The present study evaluated the survival, haematological, and oxidative stress responses of three freshwater fish species—Labeorohita, Catlacatla, and Cyprinus carpio—exposed to acidic and alkaline pH conditions under controlled laboratory settings. Acute static-renewal bioassays were conducted across a pH gradient of 4.0–10.5 to establish 24-, 48-, 72-, and 96-h median lethal pH (LC50) values, followed by sublethal chronic exposure at control (pH 7.5), acidic (pH 5.5), and alkaline (pH 9.5) treatments for 15, 30, and 60 days. Cyprinus carpio exhibited the broadest pH tolerance and Catlacatla the narrowest across all durations. Sublethal exposure produced progressive, significant reductions in erythrocyte parameters (RBC, haemoglobin, haematocrit) and a compensatory leucocytosis in both treatments, with acidic conditions generally more disruptive than alkaline conditions of comparable magnitude. Oxidative stress biomarkers in gill, liver, and kidney tissue showed a biphasic pattern of antioxidant enzyme induction followed by exhaustion, accompanied by progressive lipid peroxidation and glutathione depletion, with gill tissue emerging as the most sensitive. These findings establish a quantitative, multi-tiered characterisation of pH-induced physiological stress in regionally important freshwater fish species and provide a scientific basis for locally relevant water quality criteria and conservation planning in coal mining-affected central Indian freshwater systems.