Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures

The Effect Metabolic Rate on Choice of Group Size in a Gregarious Coral Reef Fish

Event Name/Location

Society for Experimental Biology Annual Conference / Gothenburg, Sweden

Presentation Date


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Group living comes with a variety of tradeoffs associated with food acquisition and predator avoidance. Individuals in larger groups may experience less predation risk but greater intraspecific competition for food resources. In addition, individual animals within a species vary widely in metabolic requirements, such that some individuals must feed more than others. A possible outcome is that individuals with a higher metabolic rate might be less social, or prefer to associate with smaller groups of conspecifics as the costs of competition may outweigh the benefits of predator avoidance. We studied these issues in redbelly yellowtail fusilier, Caesio cuning, a gregarious coral reef fish. The metabolic rate of all individuals was estimated via intermittent flow respirometry. Fish were then tested for sociability in a rectangular arena, where they were given a choice between associating with groups of various sizes (2 fish versus 5 fish; 2 fish versus 0 fish; and 5 fish versus 0 fish). All fish were tested under all three experimental conditions. Trials were recorded and analysed using automated tracking software to determine the amount of time in proximity to each shoal size. Early analyses suggest that fish with a higher SMR prefer smaller groups, most likely due to a higher prioritisation of foraging and a reduction in competition. This effect may also interact within baseline sociability as opposed to preference for shoal of a particular size per se. These results provide insight into the costs and benefits of group behaviours and the mechanistic underpinnings of sociability and group formation.

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