Direct and indirect effects of invasive lionfish on coral-reef cleaning mutualists

Cleaning mutualisms are ubiquitous interactions on coral reefs involving cleaner fishes and shrimps that remove external parasites from cooperative fish clients. Despite their ecological importance, nothing is known regarding how cleaning mutualisms are affected by the invasion of Atlantic coral reefs by the Pacific red lionfish Pterois volitans. Lionfish are generalist predators that may consume both cleaners and clients, with potential cascading effects on native communities. To determine whether invasive lionfish affect cleaning mutualists, I conducted a before-after-control-impact experiment manipulating the presence of lionfish on patch reefs in the Bahamas. The addition of lionfish to reefs did not significantly affect the survival and growth rates of the predominant obligate cleaner on experimental reefs, the cleaner goby Elacatinus genie. However, lionfish affected juvenile bluehead wrasse Thalassoma bifasciatum, a facultative cleaner whose density was 33% less on reefs with lionfish versus those without. The decline of bluehead wrasse was most likely due to predation by lionfish. Also, the presence of lionfish affected large transient clients, i.e. species that move among reefs; their density was 78% less on reefs with lionfish versus those without. The decline of transient species may be an indirect effect of lionfish consuming non-goby cleaners and prey, fishes that would otherwise cue transient species to aggregate at reefs. The cleaner goby is among the few small fishes on invaded reefs to escape predation by lionfish. However, by consuming other cleaners, invasive lionfish may nonetheless alter native reef communities and ecosystems.