Invasive Pacific lionfish Pterois volitans reduce abundance and species richness of native Bahamian coral-reef fishes

Pacific red lionfish Pterois volitans, introduced to Atlantic waters in the 1980s, represent a particularly successful invasive marine predator with strong effects on native prey. Previous experiments examining the effects of lionfish on native fish communities have been conducted on small patch reefs. However, the effects of lionfish on native reef-fish communities over larger spatial scales -scales at which conservation and management efforts are typically applied -have not been examined experimentally. Beginning in June 2009, I conducted a large-scale field experiment near Lee Stocking Island, Bahamas. Ten large (1400 to 4000 m 2 ) coral reefs were paired based on location and similarity of habitat, and baseline surveys of their fish communities were conducted. Quarterly removals of lionfish were then conducted on 1 reef in each pair, while the densities of lionfish on the other reefs were standardized at typical post-invasion levels. Through August 2010, quarterly surveys showed that lionfish caused significant changes in native reef-fish communities, including reductions in the total density (up to 46.3 13.7%, mean SEM), biomass (31.9 10.7%), and species richness (21.4 9.1%) of prey-sized fishes (all individuals <10 cm total length). Lionfish also caused substantial reductions in the biomass of prey-sized herbivorous fishes (33.9 16.0%) and piscivores (98.6 39.5%). However, these negative effects on small fish did not translate to observable declines in a larger size-class (all individuals 10 to 20 cm total length) over the 14 mo study period.