This Beautiful But Destructive Fish Is Resorting to Cannibalism

By Katie Pyzyk, National Geographic

PUBLISHED July 23, 2015

CONCH KEY, Florida—Fisherman Gary Nichols, who has been finding lionfish in his lobster traps off the Florida Keys for years, has noticed something different this year: Lionfish are eating each other.

“When you bring them up from those depths, lionfish spit out what’s in their stomachs, and I noticed quite a few of them regurgitating other lionfish. I didn’t even have to gut them to see it because they’re still in their mouths,” Nichols says. “They’re pretty incredible eaters so I’m not really surprised.”

Cannibalism may seem like nature’s way of coping with Florida’s growing lionfish invasion, but it is unlikely to offer a cure.

Visually stunning with their maroon and white stripes and long, fanlike fins, lionfish are considered the most destructive exotic species in marine waters off Florida and the Caribbean. They have voracious appetites and consume dozens of organisms in one feeding, drastically reducing other fish populations and altering delicate reef ecosystems.

In addition, lionfish can lay up to 30,000 eggs every four days, and their venomous spines leave them with no known predators in Florida waters.

DNA evidence has confirmed that lionfish in Caribbean waters are engaging in cannibalism, and researchers are trying to determine if it's because the fish is depleting its existing foods, such as gobies and snapper.
 Picture of a lionfish in the Red Sea

Cannibalism Is Rare

Off the Florida Keys, Nichols used to find shrimp and other small invertebrates in his lobster traps, but he has noticed a steep decline. He suspects that lionfish are eating the crustaceans, and because that can’t satisfy them, they are resorting to preying on each other.
Picture of a lionfish in the Red Sea

"I've seen a lot bigger lionfish [this year] and I'm seeing lionfish full of lionfish," he says. "They're eating all the little stuff up. I think because they've eaten up most of their food sources... now they're eating other lionfish."

Cannibalism does occur in some species of reef fish, but it is rare, according to marine scientists. A study of stomach contents discovered cannibalism in four of 130 lionfish collected in the Bahamas, with similar results from a study of 157 in Mexico.

Due to a lack of research, it's unclear if lionfish cannibalism is holding steady or increasing.

"If we saw an increase in cannibalism that could mean that there are so many lionfish that lionfish are controlling themselves, but I don't think it's reached that point yet," says Nova Southeastern University marine researcher Matthew Johnston, who tracks lionfish population trends. "It would be interesting to see over time if there's an increase, because I would think that would mean that they're getting close to their carrying capacity for that particular area."

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