Effects of food quantity on aggression and monoamine levels of juvenile pufferfish (Takifugu rubripes).

Aggressive behavior is important for animals to obtain limited resources. Understanding fish behavior and physiological response is of great significance to evaluate aquaculture production and fish welfare. Food is an important trigger of aggressive behavior in juvenile fish under high-density aquaculture conditions. The aim of this study was to investigate the aggressive behavior and monoamine levels of juvenile pufferfish (mean body mass of 6.29 ± 0.33 g) under normal feeding and restricted feeding. Our main results included the following: (1) The mortality and fin damage were higher and aggression was more intense of juvenile pufferfish at the 1% ration than those of the 3% ration; (2) during feeding, the velocity, body contact, and activity at the 1% ration were significantly higher than that of the 3% ration; (3) the concentrations of brain 5-hydroxyindoleacetic acid (5-HIAA) and monoamine oxidase A (MAOA) at the 1% ration were significantly lower, and dopamine (DA) concentrations were significantly higher. These results suggest that juvenile pufferfish shows serious aggressive behavior at the low ration, which may be related to the decrease of 5-HIAA and MAOA concentrations, and the increase of DA concentrations.