Valerio Sbragaglia, Josep Alós, Kim Fromm, Christopher T. Monk, Carlos Díaz-Gil, Silva Uusi-Heikkilä, Andrew E. Honsey, Alexander D.M. Wilson, Robert Arlinghaus

In fisheries worldwide, larger fish are subjected to substantially greater fishing mortality than smaller fish. Body length and behavioral traits are often correlated, such that fisheries-induced changes in either behaviour or morphology can also alter other traits as result of direct or indirect selection. Consistent behavioral differences among individuals, known as personality traits, provide the proximate framework by which selection can act; however, empirical evidence regarding how size-selective harvesting alters mean personality traits in exploited stocks is scarce. We examined three experimental lines of zebrafish (Danio rerio) that were exposed to positive, negative or random size-selective harvest over five generations to investigate whether simulated fishing changed the mean personality of the survivors five generations after harvesting was halted. We found that females mean boldness (defined as risk-taking tendency), activity and sociability were significantly altered relative to a randomly harvested line; however, harvest-induced changes in personality were only detected in the negatively size-selected line, in which 75% of the smallest fishes were harvested. By contrast, we did not find evidence for harvest-induced evolution of personality in the positively size-selected line, in which 75% of the largest fishes were harvested. We conclude that size-selective harvesting alters individual fish personality in a social fish.