Temperature-induced biochemical and histological changes in captive Nile Tilapia, Oreochromis niloticus

Environmental temperature plays a critical role in regulating the physiological and metabolic processes of aquatic organisms. This study investigates the effects of indoor and outdoor temperature conditions on the growth performance, biochemical composition, and muscle histology of Nile tilapia (Oreochromis niloticus Linn.). Fish were cultured in an indoor system with constant temperatures (30°C) and an outdoor system with fluctuating temperatures (33.29–41.00°C). Growth metrics, including weight gain and feed conversion ratio (FCR), were significantly higher in the outdoor system, with a 99% increase in weight gain compared to indoor culture. Specific growth rate (SGR) was also greater in outdoor-reared fish (1.47 ± 0.03 %/day) than in indoor fish (0.92 ± 0.03 %/day). Biochemical analysis revealed elevated levels of protein (85.899 ± 0.118 mg/g), carbohydrate (18.504 ± 0.081 mg/g), and lipid (24.93 ± 0.028 mg/g) in muscle tissues of outdoor-cultured fish. These biochemical parameters were consistently higher than those observed in indoor-cultured fish, suggesting enhanced metabolic activity under variable but generally elevated temperatures. Histological examination showed signs of muscle tissue abnormalities in fish from both environments, potentially linked to environmental stress. Nevertheless, the superior growth performance and biochemical profiles observed in the outdoor system are likely attributable to temperature fluctuations that remained within the species’ optimal thermal range. These findings inform temperature optimization strategies in aquaculture, supporting sustainable fish production (SDG 2: Zero Hunger) and responsible management of aquatic resources (SDG 14: Life Below Water).