Effects of Temperature on Growth, Molting, Feed Intake, and Energy Metabolism of Individually Cultured Juvenile Mud Crab <i>Scylla paramamosain</i> in the Recirculating Aquaculture System

An eight-week experiment was conducted to investigate the effects of temperature (20, 25, 30, and 35 °C) on growth performance, feed intake, energy metabolism, antioxidant capacity, and the stress response of juvenile Scylla paramamosain in a recirculating aquaculture system. The results showed that the survival rate of the 35 °C group was 80.36 ± 5.92%, significantly lower than that of the other three groups (100%). The high molt frequency of mud crabs was observed in high-temperature groups, accompanied by a higher ecdysone level and ecdysone receptor gene expression but lower molt inhibitory hormone gene expression. However, the molt increment (73.58 ± 2.18%), food intake, and feed conversion efficiency showed a parabolic trend, with the lowest value found in the 35 °C group. Oxygen consumption rate and ammonia excretion rate increased with the increasing temperature, and oxygen-nitrogen ratio, lactic acid, triglyceride, total cholesterol, glucose, and cortisol peaked at 35 °C. Temperature also significantly affected the antioxidant system of S. paramamosain. Crabs in the 25 °C and 30 °C had a significantly higher total antioxidant capacity and lower malondialdehyde compared with the 35 °C group (p S. paramamosain was 28.5–29.7 °C