With no natural predators in the area, the fish are a threat to the ecosystem as the gobble up native shrimp, crab and reef fish, marine researchers say.
An aquarium favorite, lionfish have 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, the South Florida Sun Sentinel reported Monday.
Increasing numbers are becoming homebodies in the waters off Florida's Palm Beach Country, scientists say.
"These fish really stay put, at least in our system," Zachary Jud, a marine scientist at Florida International University, said. "We've had some fish that stayed in the same spot for months. The greatest distance some moved was a couple hundred feet."
Because adult lionfish tend to stay in one place, efforts to keep down their numbers by capturing or spearing them have been successful.
But care is needed as they can deliver a painful sting, although the venom is not fatal.
"We would encourage anyone not properly equipped to not handle the fish at all," said Lad Akins of the Reef Environmental Education Foundation, a marine-conservation group that organizes lionfish roundups. "I would advise fishermen who catch one to hold the fish over a cooler or bucket and cut the line."