– by Mark Vermeij (Scientific Director, CARMABI)
Indo-Pacific Lionfish (Pterois volitans/miles complex) are beautiful and elegant fish. They also pose a serious threat to one of the most valuable assets in the Caribbean – coral reefs. Lionfish are not native to the Caribbean region and in fact could not be found anywhere in the Dutch Caribbean prior to 2009.
With venomous spines, a unique hunting style, rapid reproduction cycles and only few natural predators in the Caribbean, lionfish are a formidable threat to our islands’ nature. Studies in the Bahamas have shown over a 75% reduction in juvenile reef fish in the presence of lionfish. Lionfish are quite simply voracious eating machines.
On Bonaire, the National Marine Park has taken a pro-active approach to combat the lionfish invasion. With initial lionfish inventories conducted in 2011 in cooperation with CARMABI on Curaçao to serve as a baseline, the Marine Park has embarked on an aggressive population control programme. Around 300 volunteers have been trained and licensed to hunt the lionfish in order to keep their population at a minimum and reduce the impact on coral reef communities. While complete eradication is out of the question, extensive control may buy enough time for native species and the ecosystem to adapt to the presence of lionfish.
To date, very little has been published about the impact of lionfish on the Caribbean ecosystems but a first evaluation of the lionfish removal programmes on Bonaire and Curaçao, due to be published in 2013, indicate that they really do make a significant difference. Joint studies with CIEE’s facility on Bonaire have looked at the sex ratio of lionfish removed from the reef and their stomach content to begin filling in some of these gaps.
An online application for park staff and lionfish hunters was developed to allow them to record their observations and lionfish kills on Bonaire. The application allows this data to be viewed on a map (www.lionfishcontrol.org). This gives an unprecedented insight into lionfish distribution and removal efforts, which allows park staff to begin to gauge the effects of their population control efforts. In combination with lionfish transect records and stomach content analyses, this data will give a measurement of success in combating this invasive species on the basis of which improved management strategies can be developed.
Lionfish have spread rapidly throughout the Caribbean Sea since 1985. They negatively impact native fish communities and are therefore by some considered as the most damaging invasive species in the Caribbean to date. To combat further population growth and spread of lionfish and to protect native fish communities, various Caribbean islands have started control efforts. On Bonaire, a removal programme based on volunteers using spearguns was started immediately after the first lionfish was sighted in 2009 and a similar programme was started on neighbouring Curaçao two years later. To determine the effectiveness of these removal efforts, differences in the density and biomass of lionfish were compared between areas from which lionfish were directly targeted duringremoval efforts (i.e., “fished”) and areas where they were not. Lionfish biomass in fished locations on Bonaire was 2.76 times lower than in unfished areas on the same island and 4.14 times lower than on Curaçao, 
that was still unfished at the time of this study. While removal efforts are effective at reducing the local number of lionfish, recruitment from unfished locations, i.e., those too deep for recreational diving and at difficult to access dive sites, will continuously offset the effects of removal efforts. Nevertheless, our results show that the immediate start and subsequent continuation of local removal efforts using volunteers is successful at significantly reducing the local density and biomass of invasive lionfish on small Caribbean islands.
