Comparing behavioral performance and physiological responses of Sebastes schlegelii with different aggressiveness.

In fish, aggression has significant individual differences, and different personalities exhibit distinct behavioral performances and physiological stress responses. Under intensive culture conditions, Sebastes schlegelii juveniles display severe aggression and cannibalism, causing damage to fish welfare and economic loss. Herein, we investigated the alterations in behavioral performance and physiological stress indicators of Sebastes schlegelii juveniles with different aggressiveness. The results revealed that latency to the first movement, distance to center point, mobile frequency, and immobile frequency were significantly lower in high-aggressive individuals than low-aggressive individuals. In contrast, the immobile time was significantly higher in high-aggressive individuals compared to low-aggressive individuals. PCA was performed to identify the key parameters of fish behavior. From the results of PCA, position, motion state, and physical status could be used as behavioral screening indicators for individuals with different aggressiveness. The 5-HIAA/5-HT ratio was significantly lower in high-aggressive individuals than in low-aggressive individuals. Moreover, cortisol levels were positively correlated with immobile time, and the ratio of 5-HIAA/5-HT was significantly and positively correlated with the distance to the central point. These results suggested that individuals with different aggressiveness can be effectively distinguished in a short period of time according to behavioral factors such as position, motion state, and physical status. For a single measure, the distance to center point associated with brain monoaminergic activity may be a more direct factor. The results could be a non-invasive method to measure fish aggression and fish welfare, and then build on to improve fish welfare and enhance aquaculture management.