Testing the grouper biocontrol hypothesis: A response to Mumby et al. 2013

Biotic resistance is the idea that native species negatively affect the invasion success of introduced species. We tested the hypothesis that native grouper are controlling the abundance of exotic lionfish on Caribbean coral reefs by assessing the relationship between the density and biomass of lionfish and native predators at 71 reefs in three biogeographic regions. Our results indicated that: (a) the abundance of lionfish and large grouper are not negatively related, and (b) lionfish abundance is controlled by a number of physical site characteristics, and possibly by culling. Taken together, our results suggest that managers cannot rely on native grouper populations to control the lionfish invasion. Mumby et al. (2013) objected to several aspects of our analysis and conclusions. Here we address their criticisms and argue that our original conclusions are valid.