Some Lionfish Biology

Profile of a lionfish showing the distinctive fleshy tentacles above the eyes and below the mouth. Click on image for larger view and further details.

The lionfish (scientific name Pterois volitans) is a popular saltwater aquarium fish with distinctive maroon (or brown) and white stripes, fleshy tentacles above the eyes and below the mouth, and an imposing fan of prickly venomous spines. Although not fatal, the sting of a lionfish is extremely painful. Because these fish are not aggressive toward people, contact and poisoning is usually accidental. The species of lionfish now found in U.S. waters produce a mild poisoning. Relatives of the lionfish, including the scorpionfish and stonefish, produce a much more severe poisoning; in fact, the sting of the stonefish can be fatal to humans. Today, a person with a home aquarium is more likely to be stung by a lionfish than a diver or fisherman, but they could be placed at risk if lionfish increase in large numbers along the heavily populated East Coast.

 

Look, but don't touch! Although not fatal to humans, the dorsal, anal, and pelvic spines of lionfish can deliver a painful sting, as well as cause headache, vomiting, and respiratory distress. (Photo credit: Stephen Vives)

The lionfish's sharp, slender spines are located on the dorsal, anal, and pelvic fins. A venom gland is located at the base of each spine. The venom is a combination of protein, a neuromuscular toxin, and a neurotransmitter called acetylcholine. After the fish's spine punctures the victim's skin, the venom travels up a groove in the spine and into the wound. The sting causes intense pain, redness and swelling around the wound site. Although the worst of the pain is over after an hour or two, some people report pain and tingling sensations around the wound for several days or weeks. On rare occasions, when the venom spreads to other parts of the body, people may experience headaches, chills, cramps, nausea, and even paralysis and seizures.

Lionfish are native to coral reefs in the warm, tropical waters of the South Pacific and Indian Oceans. They prey on a wide variety of smaller fishes, shrimps and crabs, and have few predators in their native range, where they occupy the upper levels of the food chain. At present, little is known about how other coral reef species in the lionfish's "adopted" environment of the Atlantic Ocean might fare against them.

For now, reef communities in the western Atlantic Ocean are unlikely to be in much danger, since the number of lionfish is still relatively small. If the population grows large, though, lionfish could damage the native ecosystems. At the same time, other factors are already causing stress to these ecosystems, and these stress factors or "stressors" tend to favor the lionfish's expansion.

Lionfish also are believed to pose particular risks to the local environment. They are hungry predators that feed on practically anything that swims. They can easily devour the young of important commercial fish species, such as snapper, grouper and sea bass, many of which use the region's "live bottom" reefs as nursery grounds. Lionfish are ambush predators and may use their outstretched, fan-like pectoral fins to "corner" their prey. They don't sting their prey, though. Their venomous spines are used mostly for defense. Scientists are concerned that lionfish could seriously reduce the numbers of prey species and/or compete with other reef predators. When a new species is introduced in an area, it can take over the niche, or role, of a native species in its ecosystem, thus squeezing it out--this process is called competition. Another important factor is that native prey species lack of experience in confronting the intimidating lionfish might make the lionfish a more effective predator.

Sand tiger sharks are possible predators of lionfish in the Atlantic Ocean, but this remains only a hypothesis. Click on image for larger view and further details.

In their native habitats in the Indian and South Pacific Oceans, lionfish are one of the top predators in the food chain, but there are often others like sharks. Therefore, lionfish have few, or no, predators in their native habitat, possibly because of the venomous spines. Another unknown piece of the lionfish puzzle is: what might prey on lionfish in its new Atlantic neighborhood? NOAA scientist Paula Whitfield has hypothesized that sand tiger sharks (Carcharias taurus) may be a possible predator of lionfish in the Atlantic. Still, questions abound on what the top marine predators in the Atlantic Ocean will make of this "new kid on the block."

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