Factors Influencing Cannibalistic Behavior of Tiger Puffer, Takifugu rubripes: Insights into Teeth and Stocking Density Aspects

The current study explored the factors influencing the cannibalistic behavior of tiger puffer (Takifugu rubripes) based on different stocking densities and tooth clipping. Two separate experiments were carried out in this study. In the experiment testing different stocking densities, fish were reared in 300 L circular tanks with different initial stocking densities of 20, 40, and 80 fish per tank. In the experiment testing tooth clipping, some fish underwent tooth clipping treatment, while the other fish without tooth clipping served as the control. The growth results showed that high initial stocking density reduced growth, while tooth clipping numerically increased final body weight by 12.63% from 71.76 ± 2.54 g to 80.82 ± 3.33 g. The Kaplan–Meier survival curve showed that during the first 20 days of the feeding trial, the number of dead fish increased rapidly in both experiments. Cannibalism-related parameters (survival rate, caudal fin damage, and bite marks on the body surface) revealed that both intact teeth and high initial stocking density increased cannibalistic behavior. Fish with intact teeth or reared at high initial stocking density had increased serum glucose and/or lactate concentrations. Increased stocking density elevated the ratio of 5-HIAA/5-HT in the brain and altered the expression of tph2 and ddc related to 5-HT metabolism. In addition, tooth clipping increased the level of brain dopamine. In conclusion, increasing the initial stocking density is a factor contributing to the increase in the cannibalism of tiger puffer. Tooth clipping alleviated cannibalism and tended to improve growth. Furthermore, tiger puffer may need about 20 days to re-establish their social hierarchy order when being relocated to a new rearing environment.