The ongoing fight against lionfish

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Lionfish were found in much higher densities in areas where lionfish are systematically removed compared to nearby marine protected areas where removal rates are minimal

The invasion

Lionfish (Pterois volitans and Pterois miles) are native to the Indo-Pacific but invaded the Caribbean in the 1980s. Since the first sightings off the coast of Florida (likely unwanted pets released by aquarium owners), the fish have spread throughout the Western Atlantic and Caribbean and can now be found as far north as New York city, and as far south as Venezuela. The spread has brought devastating results to the region’s coral reefs, due to the predatory nature of the lionfish combined with a lack of evolutionary defence mechanisms amongst prey items. The lionfish epidemic is one of the most pressing conservation priorities for the entire Caribbean, and of particular concern is their impact on ecologically and commercially important reef fish species.

The perfect predator?

A number of factors have contributed to the success of lionfish as invaders. They have a highly generalist feeding strategy, which sees them eat a wide range of prey items including over 50 species of fish and many invertebrates, and even on occasion other lionfish. Prey is only limited by their mouth size, which is large for their body size.

Lionfish are also habitat generalists. They can be found in coral reef, mangrove and seagrass habitats, and even on mesophotic reefs as deep as 1000ft. Predation rates of lionfish are low because they are well defended by their 18 venomous spines. There are no predators in the Caribbean that specialize on them but they are occasionally taken by sharks, groupers and even cormorants. Lionfish also exhibit low susceptibility to disease and parasite loading. Critically, breeding rates in lionfish are extremely high. Each individual can produce over 2 million eggs per year, and sexual maturity is reached in less than 12 months.

What can be done?

The lionfish has proved a difficult fish to control, and an ultimate solution is still being sought. Several management strategies have been tested throughout the region, with varying levels of success. For example, an attempt in Roatan, Honduras, to condition wild shark populations to lionfish as a major food source proved too ambitious to implement effectively and raised complications associated with humans actively feeding sharks in an area famous for its dive tourism.

The fact that lionfish meat is delicious suggests that fishing may be a viable solution. However, the high breeding rate of the species makes population recovery surprisingly rapid, with populations bouncing back from almost complete removal in as little as five months. This means that direct removal is only a practical option at locations where fish demand is continually high and removal can be maintained at a regular and intense level.

The predicted final range of lionfish (Pterois volitans/miles) in the Western Atlantic and Caribbean

The predicted final range of lionfish
(Pterois volitans/miles) in the Western Atlantic and Caribbean

With multiple research sites throughout the Caribbean, Operation Wallacea (OW) is well placed to join the fight against lionfish. OW is beginning a long-term collaboration with the Cape Eleuthera Institute (CEI) in The Bahamas, which is home to one of the largest lionfish research groups in the world: the Lionfish Research and Education Program (www.ceibahamas.org).

In the summer of 2013 OW scientists, led by Dr Jocelyn Curtis-Quick of CEI, began a lionfish study aimed at: (1) detailed investigations of the impact of lionfish on resident fish community structure and biomass; (2) improving our understanding of the progression of lionfish invasion through studies of morphological adaptations and gut content; and (3) the potential role of dive tourism in managing lionfish populations.

Initial results suggest an unexpected relationship between lionfish populations and both direct removal and marine protection. Lionfish were being found in much higher densities in areas where lionfish are systematically removed compared to nearby marine protected areas where removal rates are minimal. This, and other research will ultimately provide the key to unlocking the lionfish problem. One thing is clear: like so many problems in conservation, the problems we are dealing with are human-caused, and their solution will require extensive human intervention.

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