Impacts of Rising Water Temperatures on Reproductive Physiology and Spawning Success in Indigenous Riverine Fish Species

The increasing global temperatures driven by climate change have significant implications for freshwater ecosystems, particularly impacting the reproductive physiology and spawning success of indigenous riverine fish species. This study investigates how rising water temperatures influence key reproductive parameters, including gonadal development, hormonal regulation, spawning behavior, and egg viability in native fish populations. Elevated temperatures were found to disrupt endocrine signaling pathways, notably reducing levels of gonadotropins and sex steroids essential for gametogenesis. Histological examinations revealed delayed oocyte maturation and increased incidence of atretic follicles in females, alongside reduced sperm quality in males. Moreover, altered thermal regimes shortened the reproductive window and shifted spawning seasons, potentially leading to a mismatch with optimal environmental cues required for successful reproduction. Field observations and controlled laboratory experiments across multiple species, including Labeo rohita, Catla catla, and Tor putitora, indicated a marked decline in spawning frequency and fry survival rates at temperatures 2–3°C above historical norms. These changes not only threaten the sustainability of native fish populations but also have cascading effects on aquatic biodiversity and fisheries-based livelihoods. This study underscores the urgency of developing adaptive conservation strategies and thermal management practices to mitigate the effects of climate warming on freshwater reproductive ecology.