Role of Environmental Pollution in Altering Reproductive Cycles in Freshwater Fishes

Freshwater ecosystems are increasingly facing degradation due to the accumulation of pollutants originating from industrial discharge, agricultural runoff, sewage effluents, and urban waste. These pollutants, including heavy metals, pesticides, pharmaceuticals, and endocrine-disrupting chemicals (EDCs), exert significant physiological and biochemical stress on aquatic organisms, particularly freshwater fish. One of the most profound impacts of such contamination is the alteration of reproductive cycles in fish, which can lead to disruptions in population dynamics and ecosystem stability. This research explores the multifaceted ways in which environmental pollution interferes with fish reproduction, including hormonal imbalances, inhibited gametogenesis, feminization of males, decreased fecundity, and gonadal histopathology. Through a detailed review of both field and laboratory studies conducted between 2000 and 2023, especially in regions such as the Ganges and Yamuna river systems in India, this study presents evidence that even low concentrations of pollutants can significantly affect the hypothalamic-pituitary-gonadal (HPG) axis. Findings highlight the chronic impact of substances like cadmium, lead, endosulfan, and synthetic estrogens in disrupting normal reproductive functions. The paper emphasizes the ecological and evolutionary consequences of altered reproductive cycles, such as reduced recruitment, skewed sex ratios, and species vulnerability. It concludes by underlining the urgent need for pollution control policies, routine monitoring, and habitat restoration to safeguard freshwater biodiversity and ensure the long-term sustainability of aquatic ecosystems.