Fluctuations in Seasonal Patterns of Freshwater fish Heteropneustes fossilis in Some Rivers of Bareilly: Influence of Environmental Parameters on Ramganga and Nakatia Rivers

Seasonal hydrology and environmental quality are the principal factors regulating freshwater fish communities in rivers of the Gangetic plains. The present paper provides a detailed analysis of seasonal fluctuations in freshwater fish Heteropneustes fossilis in selected rivers of Bareilly district, Uttar Pradesh, with emphasis on the Ramganga River and Nakatia River system. Authentic regional numerical data indicate that water temperature in the Ramganga River varies between 20.4 and 35.9°C, pH between 8.1 and 8.8, dissolved oxygen (DO) between 5.8 and 6.3 mg/L, turbidity between 22 and 72 NTU, alkalinity between 96 and 202 mg/L, and Biological Oxygen Demand (BOD) between 5.0 and 5.8 mg/L. In contrast, the Nakatia confluence zone has shown dissolved oxygen as low as 3.07 mg/L, suggesting organic stress. Seasonal fish diversity is generally highest during monsoon and post-monsoon periods because of breeding migration, floodplain connectivity, and enhanced productivity, whereas summer and winter often show reduced abundance. Major groups include carps, catfishes, snakeheads, clupeids, and small indigenous fishes. This study concludes that dissolved oxygen, flow regime, temperature, and pollution load are the most significant determinants of fish fluctuations in rivers of Bareilly region. Conservation measures involving pollution control, habitat restoration, and seasonal fishery regulation are strongly recommended.