A short but provocative study just came out in the open-access journal PLoS ONE. As readers may or may not be aware, the Caribbean Sea has seen an invasion of lionfish over the past five to ten years. No one is sure where they came from, but they more than likely escaped from aquaria in Florida and have since been spreading. Lionfish are problematic, since they are voracious eaters of smaller fish, including juveniles of many commercially and recreationally important species, and are not restricted to just one type of habitat. They also don’t seem to have any natural predators in the Caribbean, a fact that may have something to do with their foot-long poisonous spines. Worse, we don’t even have a good idea of what controls their populations in the eastern tropical Pacific, whence they originally came.
The researchers here found suggestive evidence that large groupers might be capable of controlling lionfish populations. They compared the biomass of lionfish and groupers at 12 reef sites in the central Bahamas. Five of the sites were in a marine park where fishing is verboten, and where, as a consequence, groupers are an order of magnitude more abundant than in most of the Caribbean. They found that these protected sites had a much lower lionfish biomass.
All the standard caveats apply…correlation is not causation, small geographic area, etc. It is interesting, though, in the context of theory that suggests invasions are more likely into disturbed ecosystems. As a practical approach to lionfish management, groupers are not ideal, at least not at the moment, and the authors acknowledge as much. Based on these results, grouper densities outside of protected areas aren’t enough to have much effect on lionfish. In the absence of greatly expanded protected areas, or significant changes to grouper fisheries and management, our best bet for biocontrol is to do it ourselves. Fluffy battered lionfish, anyone?
Peter J. Mumby, Alastair R. Harborne, Daniel R. Brumbaugh (2011). Grouper as a Natural Biocontrol of Invasive Lionfish PLoS ONE, 6 (6) : doi:10.1371/journal.pone.0021510