Social isolation reduces oxygen consumption, speed of movement and social preference in wild-type Zebrafish ( Danio rerio )

Group living is a common feature of many animals and serves a variety of functions, including predator avoidance, collective foraging, and reproduction. Individuals from group-living species may face isolation from their social group in their natural environment. Prior research has shown that social isolation in zebrafish (Danio rerio), a highly social fish, results in physiological and behavioural changes, including reduced locomotor activity and loss of interest in their environment. We investigated whether social isolation was associated with differences in dissolved oxygen consumption rate, movement speed, and social preference in adult zebrafish. We subjected fish to one month of visual and olfactory social isolation, and measured metabolic rate via dissolved oxygen consumption rate before and after social isolation. A control group was not subjected to any form of social isolation but held in comparable housing. We measured movement speed and social interaction before and after social isolation using a social preference assay. We found that socially isolated fish show a significant decrease in oxygen consumption rate compared to Day 0 isolation baseline levels, whereas control fish did not show this decrease. After a month of social isolation fish also showed lower social preference, and lower movement speed. These findings could suggest reduced energy expenditure in the context of social isolation in this species. This work enhances our understanding of the physiological and behavioural consequences of isolation in social animals.