There are 10 species of Lionfish in the genus Pterois. They are members of the Scorpaenid family, which includes about 400 species of scorpionfish, stonefish, and lionfish. Most members of the family have a series of long spines hidden inside their dorsal and pectoral fins which are connected to venom glands at the base. When the fish is stepped on or molested, the skin on the fins slides back to expose the spine, which injects venom on penetration. In several species, the venom can be lethal to humans.
The Pterois group is known by a variety of names–Lionfish, Turkeyfish, Dragonfish, Zebrafish, Firefish, or Butterfly Codfish. One of these species, the Red Lionfish, Pterois volitans, is, like the other members of the group, native to the Indo-Pacific ocean regions. With its long flowing fins and its bright contrasting brownish-red and white stripes, the Red Lionfish is extraordinarily attractive, and when the saltwater-aquarium hobby exploded in the US in the early 1980’s, it quickly became popular in the pet trade and was imported from Indonesia and the Philippines in large numbers. (Even Captain Picard of the starship Enterprise had a Red Lionfish in his Ready Room.)
Unfortunately, many of the people who purchased the fish for their home aquariums didn’t really know what they were getting into. Like most members of the Scorpionfish family, the Red Lionfish has venomous spines in its pectoral and dorsal fins. Although they are not usually fatal to humans, they can give an enormously painful sting (leading to the common name “Firefish”). The Red Lionfish can also reach a pretty large size for an aquarium fish–up to 18 inches–and has a proportionately large mouth, allowing it to eat any smaller fish that share its tank (up to two-thirds its own length). As a result, it wasn’t very long before aquarium hobbyists in Florida began releasing their no-longer-wanted pets into the sea.
The first record of a Lionfish captured in Florida waters was in 1985, when a P. volitans (most likely a released pet) was found off the coast of Dania Beach. In 1992, Hurricane Andrew destroyed a local aquarium near Miami and released at least six captive Lionfish into the Bay of Biscayne; there were also reports that the hurricane had wrecked a number of outdoors holding tanks for tropical fish importers and released their contents. Within a few years, wild Lionfish were being sighted at Miami, Boca Raton, Palm Beach, and Bermuda, and by 2000 they had spread up the East Coast as far as North Carolina. The species reached the Bahamas by 2005 and had also spread to the Florida Keys–by 2010 they had gone all the way up the Gulf coast of Florida to the Panhandle, and south to the Caribbean and Mexico. By 2013 they had spread as far as Barbados and the coast of Venezuela. Genetic testing of captured Lionfish link them to populations in the Philippines, and indicate that the entire existing population here in the US is descended from fewer than a dozen breeding females, probably escaped or released captives.
In the areas where it has been introduced, the Lionfish has no known predators. The native sharks and other predators do not recognize it as a prey species, and the venomous spines protect it from most predators who might try to sample it. The females, meanwhile, are prolific breeders. They can lay up to 30,000 eggs at a time–and usually breed every month. As a result, the Lionfish’s population growth has been explosive. In some areas, the population of wildPterois volitans was observed to increase by over seven times in just four years; their population density in areas where they have been introduced is over ten times as large as in their native ranges in the Pacific.
In such densities, the fish have an enormous impact on local ecosystems. Lionfish are voracious feeders, and will happily eat any fish they can fit in their mouths–and a single adult Lionfish can eat as many as 20 smaller reef fish in half an hour. Not only do they devastate the numbers of small native reef fish, but they compete for food with larger fish such as grouper and snapper, reducing those populations as well. In many areas, Lionfish infestations have reduced local species, in both number and diversity, by over 50%, and have established themselves as the most abundant fish. One study demonstrated that Lionfish can reduce the number of smaller fish in the area by 80% in just five weeks. Officials at NOAA, the US Fish and Wildlife Service, and state environmental agencies all along the US east coast consider the Lionfish to be the single largest threat to our native marine reef environments. Most coastal states are funding frantic scientific studies of the fish in the wild, hoping to find some vulnerability or some effective method of control.
But because of their prolific breeding rate and their invulnerability to predators, Florida Fish and Wildlife officials have pretty much given up any hope of eradicating the species (it has been estimated that removing the species totally would require killing them at the rate of at least 25% of the entire population of Lionfish every month). So the goal right now is to attempt to cull as many of them as possible to try to keep their population densities at a tolerable level. Research is being undertaken to develop a fish trap that targets the Lionfish. The fish have no legal protections whatsoever, and fishermen and divers are also being heartily encouraged by the state to kill as many of them as possible. All along the coasts of Florida, periodic “Lionfish Hunts” are organized for divers and fishermen, with prizes awarded for the most Lionfish killed. These outings can remove as many as 5-6,000 fish at a time.
In another creative tactic, Florida officials attempted to make up for the Lionfish’s lack of predators by turning Florida’s citizens themselves into predators, by commissioning the writing of a number of cookbooks with Lionfish recipes (the fish have a delicate light edible flesh similar to grouper that is highly prized by those who have tried it; though the venomous spines can make catching them a bit hazardous, the venom itself is destroyed by cooking), hoping that commercial fisheries and restaurants will develop a thriving industry around the fish, thereby turning the invaders into an economic asset while removing them from the reefs. A number of fisheries in Key West are already marketing the Lionfish they accidentally catch in their lobster traps to high-end seafood restaurants in New York and Miami. One difficulty with the “catch and eat” management strategy, however, is that the Lionfish like to lurk near the bottom in shallow water, which makes it hard to net them in commercial numbers–as a result, they are usually caught by spearfishers, which makes them rather expensive.
Can human predators become an effective check to the Lionfish invasion? It remains to be seen . . .