Characterizing trophic ecology of generalist consumers: a case study of the invasive lionfish in The Bahamas

Population sizes of generalist consumers are increasing in many ecosystems because of various human activities, and it is critical to understand the trophic role of these generalist species if we are to predict how they may affect food web structure and ecosystem function. Lionfish Pterois volitans/miles have spread throughout the Western Atlantic and Gulf of Mexico and they may have significant effects on native faunal communities. We characterized the trophic ecology of lionfish in back reef habitats on Abaco Island, Bahamas, drawing on recently developed analytical tools that employ both direct diet information and stable isotope data. Although delta N-15 and delta C-13 bi-plot data appeared to suggest substantial niche overlap with native gray snapper and schoolmaster snapper, Bayesian analytical tools suggested differences in core isotopic niches among the species. This was consistent with direct diet information, as lionfish fed almost exclusively on small prey fishes and snapper fed more commonly on crustaceans. When combining empirical isotope and diet data in a simulation model, individual lionfish appear to be more specialized in their diets than schoolmaster snapper. We suggest that this pattern may be driven by high site-fidelity of lionfish, in conjunction with distinct prey assemblages at the patch scale. Lionfish are widely considered to be generalist predators, and our data reveal aspects of this trophic generality that must be considered as the role of lionfish in their invaded habitats continues to be examined.