It took as few as three lionfish to start the invasion. Or at least, that's the best guess. Genetic tests show that there weren't many. No one knows how the fish arrived. They might have escaped into Florida's waters in 1992, when Hurricane Andrew capsized many transport boats. Or they might have been imported as an aquarium curiosity and later released.
But soon those lionfish began to breed a dynasty. They laid hundreds of gelatinous eggs that released microscopic lionfish larvae. The larvae drifted on the current. They grew into adults, capable of reproducing every 55 days and during all seasons of the year. The fish, unknown in the Americas 30 years ago, settled on reefs, wrecks and ledges. And that's when scientists, divers and fishermen began to notice.
In 2000, a recreational diver saw two tropical lionfish clinging improbably to the submerged ruins of a tanker off the coast of North Carolina, nearly 140 feet below the surface. She alerted the National Oceanographic and Atmospheric Administration, which started tracking lionfish sightings in the Atlantic. Within two years, the fish had been seen in Georgia, Florida, Bermuda and the Bahamas. They are now known to live from Rhode Island to Belize.
"I've never seen any fish colonize so quickly over such a vast geographic range," says Paula Whitfield, a fisheries biologist at NOAA.
Lionfish are the first exotic species to invade coral reefs. They have multiplied at a rate that is almost unheard of in marine history, going from nonexistent to pervasive in just a few short years. Along the way, they've eaten or starved out local fish, disrupted commercial fishing, and threatened the tourism industry. Some experts believe that lionfish are so widespread that their effect on the ecosystems of the Western Atlantic will be almost impossible to reverse. Still, some people are determined to try, if only to protect those waters which haven't yet been invaded.
Lionfish are native to the warm tropical waters of the Indian and South Pacific Oceans, nearly 10,000 miles away from the Florida shore. There are many species of lionfish in the world's oceans, and they can be hard to tell apart. All the lionfish identified in the Bahamas have been Pterois volitans, and the species is now common throughout the Western Atlantic, but some closely related Pterois miles have been found as well. Scientists don't know which species was the first to invade, but both invasions started small: genetic tests of the two species in the Atlantic show very little genetic diversity.
Lionfish grow up to a foot long and sport candy cane stripes. Their sharp spines contain a powerful venom. Although a single prick from a lionfish spine can cause days of swelling, discomfort and even paralysis, Americans import thousands of lionfish every year for aquarium use.
Lionfish herd smaller fish into pockets of coral reef or up against barriers and then swallow the prey in a single strike. In their native range, lionfish eat young damselfish, cardinal fish and shrimp, among others. In the Western Atlantic, samples of lionfish stomach contents show that they consume more than 50 different species, including shrimp and juvenile grouper and parrotfish, species that humans also enjoy. A lionfish's stomach can expand up to 30 times its normal size after a meal. Their appetite is what makes lionfish such frightening invaders.