Beware the lionfish.
The pretty-but-voracious aquarium favorite, which has been gobbling other reef fish throughout the Caribbean, is swimming up South Florida's estuaries, invading the Gulf of Mexico and spreading along the South American coast.
Scientists say the East Coast has never seen a mass marine invasion of this kind before, and they worry that it will set off a cascade of ecological damage to native fish, coral reef and their delicate habitat.
Lionfish have been multiplying in the Caribbean and along the Carolina coast for more than a decade, probably after a few were dumped from somebody's aquarium off the shores of South Florida and their offspring rode north and east on ocean currents.
Now the footlong fish are coming full circle back to South Florida, carried by currents from the Caribbean.
The invader probably will establish itself along Florida's east coast and the entire Gulf Coast within the next five to 10 years and spread as far south as Brazil, marine scientists predict.
"I don't see anything stopping them," said Matthew Johnston, a research scientist at the National Coral Reef Institute in Dania Beach. He has developed computer software that tracks sightings of lionfish and projects their next movements — a model that he will put online to help researchers study this and other invasive species.
"In South Florida," he said, "the lionfish population is just exploding now."
Lionfish eat just about anything that fits in their mouth, Johnston said, and they have few, if any, predators outside their native habitat in the Pacific around Australia and Indonesia.
Scientists speculate that the East Coast invasion began in South Florida in the 1980s or early '90s when aquarium fish may have been dumped into the ocean or Biscayne Bay. Or they may have come in ballast water discharged by ships crossing from the Pacific through the Panama Canal.
They grow up to 15 inches long and have distinctive maroon- or brown-and-white zebra stripes, fleshy tentacles above the eyes and below the mouth and an imposing fan of prickly spines. The spines deliver a venomous sting, which for humans can be extremely painful for days, though not fatal.
Beachgoers and bathers have little chance of encountering the invader, which shies from humans and prefers to hang out near natural or artificial reefs, wood pilings, rocks, sea walls or underwater wrecks.
Larger native fish along the East Coast do not yet seem to recognize lionfish as potential prey, though a few species of grouper have been known to feed on them.
As a result, lionfish have reproduced with abandon. A female produces roughly 2 million eggs a year. The larvae spread quickly once caught up in the Gulf Stream, a powerful current that rushes along the Florida coast up to the Carolinas.
The only limits appear to be colder waters, which have stopped the invasion in the North Atlantic, and fresh water with little salt content. Lionfish have been sighted as far north as Long Island in New York, but they do not live long or regenerate during the winter.
Somehow, lionfish drifted toward the Bahamas, where they reproduced quickly, decimated native fish and disturbed the habitat for corals and other species in ways scientists are still discovering.
The lionfish range so far and can swim so deep — as much as 1,000 feet — that eradication is virtually impossible, said James Morris, an ecologist with the National Oceanic and Atmospheric Administration.
The best hope for containing the invasion may come from larger native fish — such as grouper — if they learn to prey on the lionfish. Meanwhile, the government is looking to human predators to take up the theme: "If you can't beat 'em, eat 'em."
The white flaky meat of the lionfish is really quite tasty, said Morris, who cited taste tests and nutritional studies. He and others are consulting with state officials about ways to encourage commercial fishermen to sell lionfish they catch rather than toss them back in the sea.
"For nutritional quality, it's very much comparable to snapper and grouper," he said. "It's one of the greener choices you could have on the menu."