The lionfish has long been a showstopper in home aquariums. In the wild waters of the U.S. Southeast and the Caribbean, it is something else: a flourishing invasive species and one of the top predators on many Atlantic coral reefs. It has no known predators there, it reproduces all year long, and a mature female releases roughly two million eggs a year — so its numbers and its range keep growing.
A lionfish. Credit: NOAA.
Why reef scientists worry
Lionfish compete for food and space with native fish such as snapper and grouper, stocks that are already overfished. Scientists also fear they will kill off helpful species like the algae-eating parrotfish, letting seaweed take over the reefs. Lionfish eat over 50 species of fish, some of them economically and ecologically important. They hunt actively, spreading their fan-like pectoral fins to slowly pursue prey and corner it.
How it got here
The lionfish's native range is the Indo-Pacific — the South Pacific and Indian Oceans, including the Red Sea — a huge area from western Australia and Malaysia east to French Polynesia and the Pitcairn Islands, north to southern Japan and southern Korea, and south to Lord Howe Island and New Zealand's Kermadec Islands, with Micronesia in between.
The lionfish's native range, shown in orange. Credit: NOAA.
As popular aquarium fish, lionfish may have been released into the Atlantic on purpose. The first was reported in South Florida waters in 1985, and after many more sightings they were documented as established in the early 2000s. They have been reported along the southeastern U.S. coast from Florida to North Carolina, and juveniles have been collected off Long Island, New York, and Bermuda. They live in almost every kind of warm tropical marine habitat, in water from 1 to 300 feet deep, on hard bottom, mangroves, seagrass, coral and artificial reefs such as shipwrecks. On a Caribbean coral reef mapping expedition in April 2015, near St. Thomas in the U.S. Virgin Islands, scientists spotted 135 lionfish in 26 dives, some as deep as 768 feet.
How to recognize one
Lionfish have brown or maroon and white stripes over the head and body, fleshy tentacles above the eyes and below the mouth, fan-like pectoral fins and long, separated dorsal spines. An adult can grow to 18 inches; a juvenile may be 1 inch or smaller. Their fins count 13 dorsal spines, 10-11 dorsal soft rays, 3 anal spines and 6-7 anal soft rays. Their scientific names are Pterois volitans (red lionfish) and Pterois miles (devil firefish), and they also go by names such as zebrafish, firefish, turkeyfish and butterfly cod.
A lionfish's cycloid scales — oval, smooth-edged, each overlapped by the one in front, which gives the fish flexibility. Credit: NOAA.
How it lives
Lionfish are slow and conspicuous, so they rely on their striking colors and fins to put off predators. They are thought to hunt at night, but in the Atlantic they have been found with full stomachs during the day, and are often seen moving about in daylight, alone or in small groups. They swim by slowly rippling the soft rays of their dorsal and anal fins, and sometimes rest in ledges and crevices.
In their native range they are not listed as threatened or endangered, though pollution on coral reefs could reduce the crustaceans and fish they eat. Economically, they matter far more to the aquarium trade — especially in the U.S. — than as food.
Handle with care
A lionfish's spines deliver a venomous sting that can cause extreme pain for days, along with sweating, breathing trouble and even paralysis. The venom — a mix of protein, a neuromuscular toxin and the neurotransmitter acetylcholine — sits in glands in two grooves along each spine. If you are stung, get medical attention immediately.
Sources
Based on "What is a lionfish?" from NOAA's National Ocean Service, a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from oceanservice.noaa.gov
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