Lionfish

The red lionfish is a venomous coral reef fish, mainly native to the Indo-Pacific region, including the western and central Pacific and the coast of western Australia. White stripes alternate with red, maroon or brown ones, and long fins give a mane-like look. Venomous spines on the dorsal, pelvic and anal fins deter most predators. Largely solitary and mostly nocturnal, it hunts from late afternoon to dawn, cornering crustaceans and small fish with its large fins before swallowing them whole. It has become invasive in the Caribbean, the western Atlantic and parts of the Mediterranean, where few predators are known.

About the lionfish

The red lionfish is a venomous coral reef fish in the scorpionfish family, Scorpaenidae, native to the warm Indo-Pacific. Its long, striped fins fan out like a lion's mane. Released from aquariums, it has become a significant invasive species along the U.S. East Coast, the Gulf of Mexico and the Caribbean.

Its scientific name is Pterois volitans, and volitans means "flying," probably a reference to the huge, wing-like pectoral fins. Carl Linnaeus first described it in 1758 from Ambon Island in Indonesia. It is one of five species in the genus Pterois. A genetic study suggests the red lionfish may have arisen from hybrids between the common lionfish, Pterois miles, and Russell's lionfish. The red lionfish and P. miles are the two species that have become invasive in the Atlantic, and about 93% of the invasive population is red lionfish.

The body is banded in white alternating with red, maroon or golden-brown stripes, and the dorsal and anal fins carry rows of dark spots on a clear background. Bony ridges cross the cheeks, small flaps partly cover the eyes and nostrils, and a fleshy "tentacle" sits above each eye.

The red lionfish is one of the largest lionfish, reaching up to 47 cm (18.5 in), while juveniles are usually under 2.5 cm (1 in). It carries 13 venomous spines on the dorsal fin, 2 on the pelvic fins and 3 on the anal fin. Together with 14 long, feathery pectoral rays and other non-venomous fins, they create the mane-like look that gives the fish its name. Having 13 dorsal spines rather than 12 helps separate it from other scorpionfishes.

Behavior and diet

Lionfish are mostly nocturnal. By day they hide in caves and crevices among rocks and coral. At night they glide slowly over the reef, moving by rippling the soft rays of their dorsal and anal fins. Juveniles live in small groups, but adults spend most of their lives alone and defend their home range against other lionfish and other fish, using their venomous spines. Males are more aggressive than females.

How lionfish hunt

Lionfish are voracious predators near the top of the food web on many reefs. They eat mostly crustaceans, such as amphipods, isopods, shrimp and crabs, along with other invertebrates and small fish, including young lionfish. On average a red lionfish eats about 8.2 times its own body weight in a year.

They hunt mainly from late afternoon to dawn. Sunset is ideal because day fish are heading for shelter while night fish are emerging, so there is plenty of prey on the move. A lionfish rises slowly along rock and coral, using its spread pectoral fins to hide the motion of its tail and to corner prey. Its stripes, so obvious in an aquarium, blend into branching coral, feather stars and sea urchins on a reef.

One tactic is a slow, persistent pursuit. Even though many of its prey can swim twice as fast, the lionfish keeps up an uninterrupted slow approach and closes the gap whenever the prey pauses. Within about 9 cm (3.5 in), it strikes by rapidly expanding its mouth and creating low pressure inside, sucking the prey in whole. The gulp is so quick that other fish in a school may not notice a member has vanished.

Venom and defense

The venomous spines are purely defensive. Lionfish are slow swimmers, so when threatened they turn their spines toward the attacker, even if that means swimming upside down. Rival males also use them: a courting male faced with an intruder spreads his fins, points his spines forward, shakes his head and then charges to bite, sometimes getting stung himself.

Breeding

Lionfish gather only to court, usually one male with several females in groups of 3 to 8. Ready-to-spawn males turn darker, while females become paler with a silvery belly and mouth. Courtship starts just before dark. The male circles the female several times, then the pair rise toward the surface, sometimes dropping back and rising again, before she releases two hollow mucus tubes of eggs that swell into floating balls 2 to 5 cm (0.8 to 2 in) across.

A female can release up to 30,000 eggs in one spawning, and lionfish reproduce monthly, with more eggs laid in warm months. The larvae hatch about 36 hours after fertilization and are already good swimmers within a few days, and this larval stage lets the species spread quickly to new areas.

Range and habitat

The red lionfish is native to the Indo-Pacific: the western and central Pacific, the waters off western Australia, and from Malaysia east to the Marquesas Islands, north to southern Japan and southern Korea and south to Lord Howe Island. It lives mainly on reefs in warm tropical seas.

In the Atlantic it is an introduced species. It was likely first released off Florida in the early to mid-1980s, almost certainly from the aquarium trade. Adults are now found along the East Coast from Cape Hatteras, North Carolina, to Florida, in the northern Gulf of Mexico, Bermuda and the Bahamas, throughout the Caribbean from Cuba and Puerto Rico to Belize, Honduras, Colombia and Mexico, and as far south as Brazil's Fernando de Noronha. It has also appeared in the eastern Mediterranean.

Conservation status

The red lionfish is listed as Least Concern on the IUCN Red List, assessed in 2016. It has no special U.S. federal or CITES status. In its native range, one concern is reef pollution, which is expected to kill many of the fish and crustaceans lionfish depend on.

In the Atlantic, the lionfish itself is the problem. Few predators there recognize it as food. Lionfish have turned up in the stomachs of Nassau and tiger groupers in the Bahamas, but the Nassau grouper is critically endangered and unlikely to make a dent. Meanwhile lionfish have outcompeted and filled the niche of overfished snapper and grouper, and their huge appetite and varied diet are disrupting reef food chains, lowering fish numbers and reducing coral reef diversity.

Because no definitive predator keeps them in check, many organizations encourage people to catch and eat lionfish, and organized lionfish derbies have been studied as a way of managing the invasion through public participation.