Effects of a superoptimal temperature on aquacultured yellowtail Seriola quinqueradiata

This study aimed to investigate the effects of a superoptimal temperature on growth, body composition, body size heterogeneity, and relationships among these factors in juvenile yellowtail. Fish (mean body weight?=?24 g) were tagged individually and reared for 70 days under two different water temperature regimes [optimal (25 °C) and superoptimal (30 °C)]. After rearing, fish reared at 30 °C showed lower survival, less food, feed and protein utilization, significantly lower growth performance, and a lower hepatosomatic index than fish raised at 25 °C. Variations in body indices among individuals were larger for fish reared at 30 °C than for fish reared at 25 °C. Mean whole body protein content was significantly lower in fish reared at 30 °C than fish reared at 25 °C. In addition, several glucogenic and/or aromatic amino acids were lower in fish reared at 30 °C than in fish reared at 25 °C. Whole body lipid levels tended to be lower in fish with lower body weight reared at 30 °C. These results suggest that fish raised at 30 °C will have lower growth performance, and lower concentrations of specific amino acids. Moreover, heterogeneity in body size and body lipid content is expanded by a superoptimal temperature.