WASHINGTON — The very greedy lionfish has found a new home in the brackish waters of South Florida's estuaries -- and it has moved in for keeps, marine scientists are discovering.
Like a hungry guest at a holiday party, this invasive species from the South Pacific rarely strays from its food supply. Lionfish grow quickly, up to 19 inches long, partly because they have no natural predators in this hemisphere and can focus on gobbling up native shrimp, crab and reef fish.
And while they are not likely to swim up to humans, they won't back away when confronted and can deliver a painful sting.
The latest research findings – that lionfish tend to stay put for long periods – indicate that their numbers can be controlled by localized attempts to capture or kill them. Federal and local conservation leaders have given up trying to eradicate them but hope to reduce their numbers in critical places, such as marine sanctuaries, inlets and waterways where other fish reproduce.
The lionfish, an aquarium favorite, has been spreading for years from South Florida north to the Carolinas, south to Venezuela, east to the Caribbean islands and west along the Gulf Coast to Texas. But increasing numbers have been found around the docks, pilings and seawalls of the Loxahatchee River in Palm Beach County, a sign they may be populating other South Florida estuaries.
"These fish really stay put, at least in our system," said Zachary Jud, a marine scientist at Florida International University, who has tagged fish to track their movements in the Loxahatchee. "We've had some fish that stayed in the same spot for months. The greatest distance some moved was a couple hundred feet."
Jud's findings indicate that adult lionfish do not swim to colonize other parts of the coast. Instead, he believes, their larvae drift in ocean currents for weeks, then settle wherever they happen to arrive as little fish.
"It means that if you go out and kill all those fish in a given area, more adult fish aren't going to just go in to take their place," Jud said. "You are going to get some replacements, but they will start out as tiny juveniles that grow up. The reason that's important is that the bigger the lionfish gets, it's going to eat more, eat more often and eat bigger prey. So a small lionfish is less harmful than a big lionfish."
Because adult lionfish tend to stay in one place, teams of divers have been somewhat successful in keeping down their numbers along the South Florida coast by capturing or spearing them.
"Roundups" or "derbies" designed to hunt lionfish come with warnings: wear puncture-proof gloves, avoid reaching blindly into crevices where they might lurk and beware of their painful sting, which can produce severe swelling.
Lionfish are mainly a threat to smaller fish. But they can be a nuisance to divers, who encounter them when exploring underwater wrecks or artificial reefs, and to fisherman who pull them out of the sea.
Scientists and divers say the lionfish will not aggressively swim up to humans, and their venom is not fatal. But they also don't retreat when confronted and need to be avoided or handled with great care to avoid stings from the spines along their backs.
"We would encourage anyone not properly equipped to not handle the fish at all," said Lad Akins of the Reef Environmental Education Foundation (REEF), a marine-conservation group based in Key Largo, which organizes lionfish roundups. "I would advise fishermen who catch one to hold the fish over a cooler or bucket and cut the line."
Akins, a diver who has been stung several times, said the best treatment is to apply very hot water to the sting area.
REEF plans more roundups off the shores of Broward, Palm Beach and Miami-Dade counties during diving season between May and November, as well as in the Bahamas.
"Divers are doing a good job of keeping the numbers down around popular dive sites," Akins said. "But I'm sure the numbers are still increasing [elsewhere.]"
Knowing that lionfish cannot be eliminated – but also that they're tasty -- the National Oceanic and Atmospheric Administration has resorted to a strategy dubbed "If you can't beat 'em, eat 'em." Fishermen are encouraged to haul them in to cook or sell. Some restaurants in the Florida Keys have put lionfish on their menus. And REEF has published "The Lionfish Cookbook," with 45 recipes.
"In time, other fish are going to slowly realize that lionfish are edible, and they are going to start feeding on lionfish," Jud said. "And in time, prey fish are going to start to realize that lionfish are something to avoid."
"That might take a couple of decades," he said. "In the meantime, we need to realize that they are here to stay and make the best of it."