Abstract:
Salinity intrusion poses a significant threat to freshwater ecosystems and native species, including the ornamental fish Haludaria fasciata from the rivers of the Southern Western Ghats, India. This rising salinization is primarily driven by climate change-induced sea level rise, anthropogenic activities such as land-use change and pollution, and hydrological modifications from dam construction and groundwater extraction. Collectively, these stressors degrade habitat quality and threaten the survival of sensitive freshwater fauna. This study investigated the physiological and biochemical responses of H. fasciata to varying salinity levels, focusing on both gill histopathology and liver antioxidant enzyme activity to inform aquaculture and eco-physiological strategies. A 45-day survival experiment assessed salinity tolerance thresholds, with complete mortality observed at 8 and 10 ppt, while a 21-day study examined acute biochemical and histological responses at sublethal salinities (0-6 ppt). Liver biochemical analyses revealed elevated catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) levels, indicating oxidative stress, alongside alanine aminotransferase (ALT) activity, reflecting metabolic adjustments. Gill damage, including lamellar fusion and epithelial lifting, was associated with compromised respiratory efficiency and ion regulation. This study identified physiological thresholds for salinity stress management by evaluating both gill and liver responses. Along with contributing to ecophysiology and aquaculture management, the findings offer valuable insights into conservation strategies for maintaining species resilience in salinity-impacted habitats.
