Invasive lionfish: The worst case scenario

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Scientists have painted a pretty grim picture of what could happen should the invasive lionfish outbreak in the Atlantic and Caribbean go unchecked.

In a study to be published in a forthcoming issue of the journal Environmental Biology of Fishes, Mark Albins and Mark Hixon describe a possible "worst case scenario" in which the direct and indirect effects of lionfish could combine with the impacts of pre-existing anthropogenic stresses to significantly alter coral reef communities there.

Invasive lionfish (Pterois volitans) exhibit high individual growth and reproductive rates, and are also highly efficient predators. As well as being efficient predators, invasive lionfish themselves appear to be both impervious to predation and effective competitors, as well as being resistant to parasitism.

Reviewing published information available on the biology of the lionfish, as well as basing their hypothesis on the results of experiments carried out in the field, the authors posit that lionfish would significantly decrease populations of small reef fishes through predation: previous experiments as well as those conducted by the authors indicated that lionfish significantly decreased reef fish recruitment, and are capable of reducing the abundance of small reef fish by up to 90%.

Indirect effects of lionfish predation on the coral reef community may be even more devastating, given that their prey include herbivores that prevent seaweeds from outcompeting coral.

This impact could be exacerbated, as the top predators that may control the lionfish are themselves stressed by overfishing. Besides possible indirect effects of invasive lionfish on corals, the decline of other mid-sized predators via predation by or competition with lionfish, could destabilise populations of still other reef fishes.

Overall, the authors posit a worst case scenario in which most of the reef fishes are replaced by lionfishes, leaving invaded reefs depauperate of native fishes, except for those species that are not susceptible to lionfish predation. Such survivors could include sharks and rays, tunas and other transient predators, puffers and relatives, and scattered survivors of species that live and spawn in areas inaccessible to lionfish.  

Unfortunately, overfishing of large predators by humans in many regions may lead to declines of species that may be naturally resistant to lionfish predation, and those that could possibly learn to consume and thereby control lionfish abundance.

In the worst case scenario, the geographic range of invasive lionfish would eventually be limited only by water temperature and associated physiological constraints, with gradual expansion due to ocean warming.  Combined with the accelerated demise of corals due to overfishing herbivores, coral bleaching, and local environmental degradation, the resulting reef ecosystems could become vastly different from even the present despoiled state.

For more information, see the paper: Albins, MA and MA Hixon (2011) Worst case scenario: potential long-term effects of invasive predatory lionfish (Pterois volitans) on Atlantic and Caribbean coral-reef communities. Environmental Biology of Fishes doi:10.1007/s10641-011-9795-1

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