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The Indo-Pacific lionfish, Pterois volitans, has invaded most of the Tropical Western Atlantic in the last few years. The degree to which populations of this invasive species can be controlled by native predatory fish (mostly grouper), is controversial with conflicting reports. Here, we review the evidence of two recent papers and point out some of the difficulties in inferring predator-limitation purely from observational data. A negative relationship has been found between large-bodied grouper and lionfish during early colonisation though the degree to which this is caused by direct predation versus behavioural mechanisms is unclear. Evidence to the contrary from a recent study suffers confounding effects of habitat quality, fishing, and dispersal and therefore remains equivocal.