Lionfish (Pterois volitans) have invaded the majority of the Caribbean region within five years. As voracious predators of native fishes with a broad habitat distribution, lionfish are poised to cause an unprecedented disruption to coral reef diversity and function. The success of lionfish is partly attributable to its resistance to predation, largely because of its elaborate portfolio of venomous spines.

Controls of lionfish densities within its native range are poorly understood, but they have been recorded in the stomachs of large-bodied Caribbean groupers (Epinephelus striatus and Myceteroperca tigris). Whether grouper predation of lionfish is sufficient to act as a biocontrol of the invasive species is unknown, but pest biocontrol by predatory fishes has been reported in other ecosystems. The use of predatory fishes for controlling invasive species has been used in other ecosystems, but has not previously been described for coral reefs.

Groupers were surveyed along a chain of Bahamian reefs, including one of the region’s most successful marine reserves which support the top one percent of the Caribbean grouper biomass. The total amount of lionfish showed a multiple reduction in relation to the amounts of groupers. While Caribbean grouper appear to be a biocontrol of invasive lionfish, the overexploitation of their populations by fishers, means that their median biomass on Caribbean reefs is an order of magnitude less than in our study. Thus, chronic overfishing will probably prevent natural biocontrol of lionfishes in the Caribbean.

Although the study doesn’t give any clear answer to if grouper can be one solution to the lionfish problem, it could be a contributor. This also would give the grouper a higher status and offer more protection for this species. There remains much to learn about the scope for biocontrol of lionfish.

Further laboratory and field trials are needed to understand the size-dependency of the predator-prey relationship and the role that small-bodied grouper and other fish may play, particularly in preying upon juvenile lionfish. The scientists also observed that lionfish appeared to remain closer to its hideouts at sites with high grouper densities, suggesting that grouper may both reduce lionfish densities and reduce the predation rates of lionfish in the area.

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