The effectiveness of small-scale lionfish removals as a management strategy: effort, impacts and the response of native prey and piscivores.
Lionfishes (Pterois volitans and P. miles) are now established in all regions of the Caribbean, Gulf of Mexico and the Western Atlantic. As they continue to spread and colonize, reef ecosystems could be undergoing significant changes in species composition. A successful method of control includes targeted removals, but many organized removal efforts occur on large spatial scales, or involve numerous volunteers and personnel. This study addressed the effectiveness of lionfish removal over small spatial scales on a linear coral reef in La Parguera, Puerto Rico and quantified the effort necessary to diminish and maintain low lionfish densities. Three removal events at this reef took place over one month with 11 hunters per day to cull a 14,520 m2 area. Timing of recovery of lionfish density varied by area in the removal site, but an overall reduction in lionfish biomass was retained post-removal. Tagging of lionfish in non-removal sites suggested recovery to the culled area was due to re-colonization via recruitment or ontogenetic migration rather than by adult lateral immigration. No detectable effects of the lionfish removal were observed on native prey or piscivore densities. Thus, evidence from this study supports that native fish abundance may not be impacted when lionfish densities are relatively low. Removal efforts should consider lionfish density relative to the densities of the native faunal communities before committing resources to this strategy.