Lionfish Control: Targeted Areas, Lots of Manpower

Invasive lionfish may never be eradicated in the Caribbean, , but a new University of Florida study shows that it may be possible to keep them under control -- in specific, targeted areas and using plenty of manpower.

Efforts have been made to control the fish by holding derbies, where divers and snorkelers spear or net as many fish as possible. The study, outlined in the Reviews in Fisheries Science, attempted to determine how intense and consistent such efforts would need to be to curb a lionfish population.

The Florida researchers spent much of 2011 working with the Central Caribbean Marine Institute, local divemasters and scuba volunteers who removed lionfish weekly from several sites off Little Cayman Island. The team asked the divers not to remove lionfish from an area called Rock Bottom Wall so it could be used as a control site. At the lionfish removal sites, lionfish density decreased , and the average size of the remaining fish was smaller. In comparison, lionfish numbers increased markedly at the control site.

When the study began, it wasn't unusual to capture lionfish measuring about 400 millimeters long. But by June 2011, at the dive site Blacktip Boulevard, the removed fish ranged from 140 to 295 millimeters in length, with 83 percent of the fish smaller than 220 millimeters. The size of the fish has food chain implications, as the larger lionfish are more likely to consume bigger prey, such as grouper or snapper, while smaller lionfish prefer to nibble on shrimp.

The study's findings have laid the groundwork for future studies into ecological impacts of lionfish on native fish populations and the cost-effectiveness of removal efforts, said Tom Frazer, head of the Florida research team. "You're not going to be able to determine how many resources you can use for that problem until you have an idea how much time and effort is involved in removing the fish."