Exploring Rearing Water Temperature Conditions for Inducing Body Growth without Water Temperature Stress in Red-Spotted Grouper (Epinephelus akaara)

This study explored appropriate rearing water temperatures that can minimize water temperature stress and induce body growth in the farmed red-spotted grouper (Epinephelus akaara). An examination of annual growth performance showed that body growth (body weight and total length) was induced faster from July to September 2020 than during other periods. Weight gain (WG), specific growth rate (SGR), and feed efficiency (FF) were highest in August 2020. The hepatocyte diam-eter increased significantly in June and October 2020. It was observed that the body weight and total length were significantly induced under the conditions of 26 degrees C and 32 degrees C. WG and SGR were highest at 26 degrees C and 32 degrees C, respectively, and FCR was highest at 26 degrees C. The expression of Cu/Zn-Superoxide dismutase (SOD) and Mn-SOD mRNA in the brain was significantly higher in the 32 degrees C group than that in the 26 degrees C group after 12 weeks. Expression of catalase (CAT) mRNA was signifi-cantly higher in the natural group than in the 26 degrees C group. The expression of Cu/Zn-SOD and CAT mRNA in the liver was significantly higher at a natural temperature at 8 weeks. The expression of Mn-SOD mRNA was significantly higher in the natural temperature group than that in the 32 degrees C group. The hepatosomatic index values and hepatocyte diameter tended to decrease more significantly at 26 degrees C and 32 degrees C. Our findings are based on growth performance and physiological indicators, and it is considered that a water temperature of 26 degrees C is suitable for farmed red-spotted groupers.