Could groupers be the answer to the lionfish invasion?

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Scientists have identified a possible natural biological control to the lionfish that are spreading like wildfire throughout the Caribbean and subtropical Atlantic.

Until now there appeared to be few viable solutions to the explosive invasion of the lionfish (Pterois volitans, together with a sister species, P. miles) throughout the region.

But now scientists from Australia, UK and USA have identified groupers (Epinephelinae) as a possible solution in serving as a natural biological control agent in a recent study published in the online journal PLoS ONE.

Peter Mumby, Alastair Harborne and Daniel Brumbaugh surveyed 12 sites along a stretch of reef spanning 30 km of the Exuma Cays in central Bahamas. 

Five of these sites were situated in the Exuma Cays Land and Sea Park, which has some of the highest biomasses of groupers in the Caribbean following a 20-year ban on fishing.

The authors found that the biomass of the lionfishes was significantly negatively correlated with that of the groupers, with the lionfish biomass in the park being seven times lower than outside the park. 

No other significant correlation was seen with other smaller-bodied predators, implying that large groupers may be the only effective biocontrol agent for the lionfish outbreak. 

There is evidence that the large groupers are eating the lionfish instead of competing with them to keep their populations down. Lionfish have been found in grouper stomachs and do not share the same food resources as large groupers (making competition very unlikely).

However, the authors caution that further studies are needed to assess the efficacy of using groupers as a biological control agent. 

It is possible that a further increase in lionfish biomass, particularly in adjacent non-reef habitats where groupers are absent, may render groupers less effective at controlling lionfish populations. 

Groupers are a valuable commercial species in the region and while they appear to have the capacity to serve as a natural biological control agent, this is only likely to be feasible in protected marine reserves or if fishing practices change to allow the maintenance of large individuals in the population.

For more information, see the paper: Mumby PJ, AR Harborne and DR Brumbaugh (2011) Grouper as a natural biocontrol of invasive lionfish. PLoS ONE 6, e21510. doi:10.1371/journal.pone.0021510

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