Red Lionfish (Pterois volitans): Facts, Venom and Invasion

What does a red lionfish look like?

A red lionfish is impossible to mistake for an ordinary reef fish. Its body is covered in vertical stripes of red, maroon or brown alternating with white or cream, and the bands continue across the head and fins. Fish living in murky coastal water and estuaries are often darker, sometimes almost black.

The most striking feature is the fins. The dorsal fin is made of long, separate spines that stand up like a mane, which gave the fish its common name. The pectoral fins are huge, feathery fans that the fish spreads like wings. Fleshy tentacles above the eyes and small flaps around the mouth break up the outline of the head, which may help the lionfish blend in with algae-covered rocks. The soft rear fins and the tail are dotted with dark spots.

Hidden among the fins are 18 venomous spines: 13 in the dorsal fin, 3 in the anal fin and 1 in each pelvic fin. The bold stripes are a warning signal, a strategy biologists call aposematism, that tells predators the fish is dangerous to bite.

Name and classification

Carl Linnaeus described the red lionfish in 1758 from specimens collected at Ambon, Indonesia, originally naming it Gasterosteus volitans. The species name volitans is Latin for “flying”, a reference to the wing-like pectoral fins. The genus name Pterois comes from the Greek word for a wing or fin.

The red lionfish belongs to the scorpionfish family, Scorpaenidae, a group of mostly bottom-living fish famous for venomous spines. Its relatives include the many scorpionfishes and, more distantly, the stonefishes. Other English names include turkeyfish, red firefish and butterfly cod.

The genus Pterois contains roughly half a dozen species, and their exact number is still debated. Genetic studies suggest that the red lionfish may have arisen long ago from hybrids between the devil firefish (Pterois miles) and Russell’s lionfish (Pterois russelii), which would explain why the species are so hard to tell apart.

How big do red lionfish get?

Red lionfish are medium-sized reef fish. Females and males look alike outside the breeding season, and size varies with age, food supply and region.

Young lionfish grow quickly once they settle, and they can become mature and start breeding within their first year. That fast start is one reason the species has been able to spread so rapidly outside its native range.

Where do red lionfish live?

In its native range the red lionfish lives on reefs from southern Japan and southern Korea south to Lord Howe Island off eastern Australia, and from western Australia and Malaysia east across Micronesia to French Polynesia and the Pitcairn Islands. Farther west, in the Indian Ocean and the Red Sea, its place is taken by the devil firefish.

It is a fish of reefs and rocky places, including lagoons, the outer slopes of coral reefs, seagrass beds, mangroves, shipwrecks, piers and harbors. In its home waters it is usually found from the shallows down to about 50 m (165 ft), but in the invaded Atlantic lionfish live much deeper, with records from mesophotic reefs at 100 m (330 ft) and below. Lionfish also tolerate brackish water and can enter estuaries.

Since the 1980s the species has become established along the US East Coast from Florida to North Carolina, around Bermuda and the Bahamas, throughout the Caribbean and the Gulf of Mexico, and along the coast of South America as far as Brazil. Cold winter water sets its northern limit, as explained in Why are lionfish invasive?

What do lionfish eat and how do they hunt?

The red lionfish is a carnivore that eats small fish, shrimps, crabs and other small crustaceans, and it will also eat smaller lionfish. It is not a picky eater: studies of lionfish stomachs in the Atlantic have found dozens of different prey species, including young parrotfish, wrasses, gobies, damselfish and the juveniles of snappers and groupers.

Lionfish are slow, deliberate hunters. A lionfish drifts toward its prey, then spreads its large pectoral fins to box the victim in against the reef. It often blows small jets of water at the prey as it closes in, which may confuse the smaller fish and turn it head-first toward the lionfish. When it is a few centimeters away, it strikes in a fraction of a second, opening its mouth so fast that the prey is sucked in and swallowed whole.

In the Pacific, lionfish hunt mostly at dawn, dusk and at night. In the Atlantic they are often seen feeding during the day as well, and they can eat large amounts of food relative to their size, which helps explain their impact on reef fish.

Behavior and venom

Red lionfish are mostly solitary. By day they often rest under ledges, in caves or among coral, hanging almost motionless with the head angled slightly down. They become more active in the evening.

The venomous spines are used only for defense, never for hunting. A lionfish feels safe enough to swim slowly in the open, and when threatened it turns its spines toward the attacker, even tilting or flipping its body so the dorsal spines point forward. Most predators learn quickly to leave it alone. The sting is very painful for people but rarely life-threatening, as explained in Are lionfish venomous?

Reproduction, life cycle and lifespan

Lionfish court at dusk and through the night. A male usually gathers several females, and courting pairs circle, follow and lead one another before rising toward the surface to spawn. The female releases two hollow, jelly-like masses of eggs, each holding up to about 15,000 eggs, which the male fertilizes in the water.

The egg masses float near the surface and drift with the currents, and the larvae hatch after about 36 hours. The larvae then live in the plankton for around a month before settling onto a reef as tiny juveniles. Because the eggs and larvae drift, ocean currents can carry young lionfish hundreds of kilometers from their parents.

In warm water a female can spawn every few days throughout the year. Estimates suggest that one female can release around 2 million eggs a year, far more than most native reef fish of a similar size. Red lionfish can live for up to about 10 years in the wild.

Predators and conservation status

In the Indo-Pacific, adult lionfish are eaten by groupers, moray eels, cornetfish and some sharks. A large ambush worm, the bobbit worm, has even been filmed catching lionfish in Indonesia. Predators of the drifting eggs and larvae are poorly known but may be important in keeping native populations in check.

In the Atlantic, most native predators did not evolve alongside lionfish and seldom recognize them as food. Lionfish have been found in the stomachs of groupers and seen being eaten by moray eels, but this has not been enough to control their numbers.

The IUCN lists the red lionfish as Least Concern. It is widespread and common across its native range, and the main human pressures there, collection for the aquarium trade and local fishing, are not considered a threat to the species.

The devil firefish in the Mediterranean

The red lionfish has a close twin, the devil firefish or common lionfish (Pterois miles), which is native to the Indian Ocean and the Red Sea. About 93% of the lionfish in the western Atlantic are red lionfish, and most of the rest are devil firefish.

The devil firefish has also invaded the Mediterranean Sea through the Suez Canal. A single fish was recorded off Israel in 1991, but the real invasion began around 2012. Within a decade lionfish had spread along the coasts of Lebanon, Cyprus, Turkey and Greece and reached the central Mediterranean, including Sicily, Malta and Tunisia. Warming sea temperatures are thought to be helping it spread.

Myths and facts

Myth: lionfish are poisonous to eat. Lionfish are venomous, not poisonous. The venom is found only in the spines, and the flesh is a popular white fish in Florida and the Caribbean, where eating lionfish is encouraged to reduce their numbers.

Myth: Hurricane Andrew started the invasion. In 1992 Hurricane Andrew damaged a seaside aquarium in Florida, and six lionfish escaped into Biscayne Bay. However, lionfish had already been seen off south Florida in 1985, years before the storm. Most scientists think the invasion came from repeated releases of unwanted aquarium fish.

Myth: lionfish attack divers. A lionfish may hold its ground or swim toward a diver with its spines pointed forward, but this is a defensive display. Stings happen when people touch, handle or brush against the fish.

Lionfish and people

The red lionfish is one of the most popular marine fish in the aquarium trade, and it is a favorite sight for divers on Indo-Pacific reefs. That popularity is also how the invasion began, which is why releasing any aquarium animal into the wild is illegal in many places.

In the western Atlantic, lionfish are treated as a serious threat to reef fish and fisheries, and they add pressure to reefs already damaged by bleaching and disease, as described in What is happening to Florida’s coral reefs? Marine parks, fisheries agencies and volunteers run organized removal efforts, restaurants serve lionfish, and some communities in the Caribbean make jewelry from their fins. These efforts reduce numbers on shallow reefs, but nobody expects to remove lionfish from the Atlantic completely.

For other species whose defenses make them famous, see the most venomous animals.