Sociable bluegill, Lepomis macrochirus, are selectively captured via recreational angling

Abstract

Individuals often show considerable variance in social behaviour and aggression, leading to defined social roles. Removal of individuals with particular roles from groups may have impacts on group function, leaving those groups less able to locate critical resources and avoid danger. In recreational fisheries, capture by humans constitutes a mortality risk, and therefore angling has the potential to fundamentally alter social structure in exploited populations if individuals with defined social roles are disproportionately captured. However, little work has examined the linkage between social behaviour and angling vulnerability. To address this gap, we conducted a study on bluegill, Lepomis macrochirus, a freshwater fish known to be socially gregarious, and a common target of recreational anglers in North America. Fish were angled in a naturalistic pond setting, and a subset of captured and uncaptured fish was then assessed for sociability in a shoaling assay and aggression/dominance in paired dyadic contests. Results showed a significant effect of time spent in the social zone on capture status, with captured individuals spending significantly more time near a transparent divider separating it from a shoal of conspecifics compared to uncaptured fish. Dominance was not associated with angling vulnerability, and sociability was not linked with dominance. Collectively, these results show that more social bluegill are more likely to be captured by anglers. This could in turn lead to decreased social functionality in exploited populations as a result of the removal of particularly social individuals, as well as possible evolution of social behaviour in exploited populations due to this selection.