Lionfish hunters are having a dramatic impact in protecting reef fish from the voracious predators, results from two years of field studies in Little Cayman show.
Researchers found that dive sites where lionfish were systematically culled had 70 percent more native fish compared to nearby sites where lionfish populations remained undisturbed.
Final results from the ongoing research project, which involves quarterly surveys of six dive sites off Little Cayman, will likely be published in a scientific journal and used to fuel future policy in combating the invasive species across the Caribbean.
Initial findings, shared with the Caymanian Compass, add weight to the belief that removal of lionfish from the ocean by divers is the most effective way to combat the invasive creatures, which are eating their way through reefs across the region. Other international research projects have failed to find conclusive evidence that marine predators could learn to feed on lionfish.
The latest project, led by the Central Caribbean Marine Institute and funded by Guy Harvey’s Ocean Foundation, focused on the impact of human intervention.
Katie Lohr, who led the project, said it was encouraging to see that reef fish were more abundant on sites where divers regularly speared lionfish.
“It’s really good news and it shows that the volunteers who have been giving their time to help our reefs are having an impact,” she said. “It really shows what kind of impact we would be seeing if they weren’t managed by humans.”
The Cayman Islands Department of Environment confirmed this week that it is not issuing any new spears to divers until it has reviewed the current volunteer culling program. Bradley Johnson, a research officer with the DoE, said the effectiveness of culling was not in question, but the department wanted to “pause and review” before expanding any further.
A previous study by CCMI and the University of Florida showed that lionfish density was consistently lower on sites where cullers were active. The latest research shows the impact that is having on other fish. Researchers say they found far greater numbers and a wider range of species at cull sites.
“We had already established that culling brings lionfish numbers down, what we are asking now is does that have a noticeable effect on native reef fish,” Ms Lohr said. “We are beginning to see that yes, it does.”
The study sites focused on 50 meter stretches along Little Cayman’s undersea wall, between 50 feet and 90 feet deep.
Three sites were off limits to hunters, while three were consistently culled.
Ms Lohr said the potential long-term benefits of the research far outweighed the short-term cost of leaving the three “control sites” untouched and therefore more vulnerable to lionfish.
She said the size of the Cayman Islands, in particular Little Cayman, meant that culling efforts had the potential to be effective in comparison with other areas, like the Bahamas, where it is much more difficult for hunters to cover wide areas of reef on sometimes remote islands.
Lionfish are prolific breeders and voracious eaters. The average lionfish eats 60,000 reef fish before it is 2 years old.
They are not native in the Atlantic and the entire population in the region is believed to originate from a small number of fish released from private aquariums in the U.S.
They have no natural predators and researchers fear their unchecked population expansion could have a devastating effect on reefs, threatening other marine species, as well as the diving and fishing industries.
“Ultimately, the information from each of the Central Caribbean Marine Institute’s lionfish studies will be integrated to create a successful and cost-effective removal-based management plan that can be applied to the Cayman Islands, as well as neighboring Caribbean islands, in the hope that they can use it to preserve their native reef biodiversity,” said the institute in a statement.
Weekend tournaments target lionfish
Two upcoming tournaments will seek to make further inroads into the lionfish invasion. The Blue Water Roundup, organized by the Cayman United Lionfish League and sponsored by RBC Wealth Management, takes place this weekend with registration on Thursday evening at Cayman Cabana.
The Central Caribbean Marine Institute hosts its second tournament in Grand Cayman on Oct. 26.
This weekend’s tournament challenges teams of between two and eight people, with at least one Department of Environment licensed lionfish culler, to gather as many fish as possible over the two-day period. At the end of each day, there will be weigh-in stations set up and awards will be handed out on Sunday for the most lionfish caught, greatest overall weight, and biggest/smallest lionfish captured.
Fish caught during the tournament will be cooked and served to participants.
Mark Orr, tournament coordinator, said: “It’s an unfortunate truth that lionfish are here to stay and that humans culling them is currently the only way to control their numbers and save our marine ecosystems. We are keen for the general public to learn how good they are to eat, and thus increase the demand for restaurants to carry lionfish on their menus, hopefully serving them instead of more threatened species, such as grouper.”