Identifying selective predation by lionfish on native reef fish along the North Carolina coast
Populations of the invasive Indo-Pacific lionfish (Pterois volitans and P. miles) have been present off the coast of North Carolina for over 10 years, yet relatively little is known about the effects that this predatory fish may be having on local native fish populations and community structure. In other western Atlantic and Caribbean regions, lionfish are abundant predators that are associated with reef fish declines. Owing to this potential for declines of native fish, understanding the potential impact of lionfish in North Carolina is essential to the effective management of North Carolina’s coastal natural resources. In this study we used published data on lionfish stomach contents and surveys of reef fish abundance along the North Carolina coast to better understand if and how lionfish may affect native reef fish communities. Using the known abundance of native fish species, we developed a simple simulation model to predict the expected stomach contents of a sample of lionfish under the assumption that they are nonselective generalist predators that feed on native fish in proportion to their abundances.
We compared these simulated expected rates of lionfish predation on 29 native fish families to what was actually observed in a sample of 309 fish found in lionfish stomachs in a previous study (Munoz et al., 2011). Using this method, most native fish families (15 out of 29) appeared in lionfish stomachs as frequently as would be expected under the assumption that lionfish are indiscriminant generalist predators. However, 5 native fish families were significantly under-represented in lionfish stomachs, suggesting that these taxa are avoided by lionfish or occur in different habitat types. Importantly, we identified 9 fish families that were found in lionfish stomachs significantly more frequently than would be expected. Of these taxa, Scaridae (parrotfish), Monacanthidae (filefish), and Synodontidae (lizardfish) had the highest standardized effect sizes, appearing in lionfish stomachs at a rate up to 52 standard deviations more frequently than expected based on our simulation model. Additional trait-based analyses suggest that presence/absence of spines, coloration, and habitat use may partially explain these patterns of predation. Our results suggest that these 9 preferred fish families, which include commercially and recreationally important fish species, may suffer disproportionate effects of lionfish establishment and predation.