Efforts to spear invasive lionfish not likely to curb population, researchers say

Jun 23, 2011 by Mickie Anderson

(PhysOrg.com) -- Lionfish are causing problems for native fish populations in Florida’s coastal waters, such as grouper and snapper, prompting efforts to try and curb populations of the invasive species.

But a new University of Florida study suggests that eradicating lionfish isn’t likely to happen without a better understanding of the species and better control strategies.

The study, published in the online journal PLoS ONE last month, showed that lionfish reproduce too quickly to be wiped out by short-term harvesting, said Andrew Barbour, a UF fisheries and aquatic sciences graduate student and the study’s lead author.

The frilly, red, black and white fish aren’t caught easily using hook and line, so lionfish derbies encourage divers and snorkelers to spear or net as many lionfish as possible in a given time frame.

Despite good intentions of those involved in short-term harvesting, lionfish will likely continue gobbling up juvenile grouper, snapper and other economically important species, he said.

The findings should prove helpful for those trying to curb the lionfish problem, Barbour said.

“It’s not news a lot of people are going to want to hear, but it’s news that needs to be out there,” he said.

Native to the Indo-Pacific, lionfish have been causing problems for years in waters off the Southeast United States and Caribbean. More recently they’ve spread to the Gulf of Mexico and South American waters.

Derbies have resulted in up to 1,400 lionfish being harvested in a day, Barbour said. But a single lionfish can produce as many as 200,000 eggs per month, easily replenishing the ’s numbers.

The researchers used mathematical modeling programs to show that 35 to 65 percent of the lionfish would have to be taken from an area every year to keep the lionfish numbers in check. And even if large numbers of lionfish are harvested, that’s not likely to happen, said Mike Allen, a UF professor of fisheries ecology and one of the study’s authors.

Lionfish populations are able to rebound easily from harvesting efforts because they reach maturity quickly, have eggs and larvae that can be spread over large geographical areas by ocean currents, and thus far, have no natural predators to help keep them in check, said Tom Frazer, a UF professor of aquatic ecology and another author of the study. Allen and Frazer are members of UF’s Institute of Food and Agricultural Sciences.

The UF scientists said it might be possible for those looking to dent the lionfish numbers to do so with intensive spearfishing in small geographic areas – such as coral reefs frequented by scuba diving tourists, Barbour said.

But those efforts will have to be sustained.

“You’d have to fish them hard, and over a long period of time,” Frazer said.

Lionfish are edible, although researchers haven’t studied the fish long enough to know whether ciguatera, a toxin that can cause human illness, might be a problem.

Thanks to their showy appearance, lionfish are popular with tropical fish hobbyists. They have venomous spines that can cause illness to humans who get poked, but the species is not aggressive and they tend to stick close to reefs or other structures they’ve claimed as their home.

There are several theories about what caused to become established in the Western Hemisphere, Frazer said. Some blame irresponsible aquarium enthusiasts for simply releasing the fish into the wild. Others suggest wind and waves from Hurricane Andrew could have freed the fish from South Florida aquariums and swept them into the Atlantic Ocean. Another theory holds that the were accidentally transported in seawater used as ship ballast.

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