Invasive lionfish increase activity and foraging movements at greater local densities

Density-dependent changes in predator foraging behavior due to intraspecific competition for food can have important implications for population dynamics of both the predator and its prey. The Indo-Pacific red lionfish Pterois volitans is an invasive predatory reef fish that has reached high population densities and can cause large reductions in small native fishes. To determine whether lionfish behavior or movement varies with local lionfish and/or prey densities, I conducted observations of lionfish on 16 coral patch reefs in The Bahamas. Lionfish foraging activity and movement varied significantly with lionfish density. At higher densities, lionfish exhibited greater activity levels, time away from shelter, and more short-term foraging movements between coral patch reefs and surrounding seagrass habitats. However, these changes were not uniform throughout the day, with differences in activity occurring only at dusk and differences in movement occurring at both dawn and dusk, but not midday. Although some lionfish foraging behaviors varied with prey density, overall lionfish density was more strongly related to differences in lionfish activity patterns. These temporal and spatial changes in lionfish foraging behaviors are consistent with the predicted effects of intraspecific competition and may have important consequences for lionfish removal efforts and native prey populations. Specifically, in areas with higher lionfish densities, prey fishes that are more active at dusk and/or inhabit seagrass beds near coral patch reefs may be more vulnerable to lionfish predation. By culling lionfish, managers may reduce the local foraging movements of lionfish and thus help maintain native fish communities in multiple habitats.