Abstract: Social interaction among group members contributes to the development of behavior and bodily tissues. It is thus of great significance to explore the mechanism, performance and influencing factors of social reward. To explore the effects of photoperiod on sociability and decision-making behavior in fish under social reward scenarios, Qingbo (Spinibarbus sinensis) and cichlid (Pseudotropheus zebra) with distantly genetic relationship, different social-interaction characteristics and distinct habitat photoperiod condition were selected as experimental objects. The parameters of behavioral characteristics to the stimulus shoal as a social reward in a six-arm maze were analyzed for both short-photoperiod-treated and control fish. The results showed that compared with Qingbo, cichlid showed stronger exploratory behavior and more group interaction activity. The decision time of group cichlids was faster than individual cichlid. Short photoperiod treatment exhibited no significant effect on personality in cichlid, but led to the decline in social interaction time with stimulus shoal and the accuracy of individual decision-making. By contrast, short photoperiod treatment resulted in increased exploration behavior, decreased group cohesion, but did not affect decision time, accuracy and group interaction activity in Qingbo. Our results suggested that the effects of photoperiod on fish behavior and population interaction differed between the two species. In general, the behavior characteristics related to personality in Qingbo were more sensitive to photoperiod treatment, whereas the decision-making strategy of cichlid was more vulnerable to such treatment. These differences might be related to the differences in social interaction pattern, personality, and photoperiod conditions of habitats between two species.

Key words: short photoperiod, Spinibarbus sinensis, Pseudotropheus zebra, decision making, bravery, cohesion