Physiological and behavioral responses to social isolation and starvation in a social fish

Changes in the social environment, such as segregating an individual who would typically reside within a social group, may elicit physiological and behavioral responses to external stimulus such as starvation. However, such changes in phenotypic traits receive a little attention in social fish. Here, we used qingbo (Spinibarbus sinensis) with high level of sociability as animal model in order to examine the physiological and behavioral responses of this fish species to social environment (isolation vs. grouping) and nutritional state (well-fed vs. starvation). We found that differences in the reduction of body masses between the group-reared and the isolation-reared fish during periods of starvation can be partially attributed to variations in water volume within the tanks. Additionally, the decrease in standard metabolic rate was more pronounced in the group-reared fish compared to the isolation-reared fish when deprived of food, except for maximum metabolic rate and aerobic scope. Interestingly, only the group-reared fish experienced a decline in constant acceleration swimming performance after food deprivation, while this was not observed in the isolated fish. Neither social isolation nor starvation had any impact on personality expression (e.g., exploration, activity, and boldness). However, both exploration and boldness exhibited temporal effects with an increase in these two personality traits. Social isolation tended to elevate anxiety-like behavior levels. Both social isolation and starvation did not affect upper thermal tolerance; however, starvation enhanced cold resistance of the fish. Our findings contribute to a better understanding of how social environment combined with trophic stress influences phenotypic traits and may offer valuable insights into animal welfare considerations for both natural habitats and aquaculture practices.