Open sores, lower numbers likely not invasive lionfish's end

NEW ORLEANS (AP) — A new disease has caused open sores that can eat into the muscles of invasive lionfish and appears to have contributed to an abrupt drop in their numbers in the northern Gulf of Mexico, scientists reported Tuesday. But they hasten to say it’s probably far from the end of the showy invader with long, venomous spines.

Lionfish may even already be bouncing back, said University of Florida doctoral student Holden Harris, lead author of the article published online in Scientific Reports. Numbers of the smallest lionfish taken by spearfishers were way down in 2018, indicating a possible reduction in spawning, but were rising late that year and in early 2019, he said.

“It's too early, really, to say if that'll become a full population recovery,” he said.

It's an interesting development, said Matthew Johnston, a Nova Southeastern University researcher who has written scientific papers about invasive lionfish but had not known about the lesions or population changes. “We've always been wondering if they're ever going to reach their limit in certain locations," he said. "To date it seemed the populations just kept getting larger and larger and larger.”

One reason lionfish are a problem outside their native Indo-Pacific is that their hunting method was new to their adopted territory, so their prey hadn't evolved countermeasures. The big-mouthed fish hover over smaller fish, then suddenly gulp them down, swallowing prey up to half their own length. Sometimes they blow jets of water to make small plankton-eaters face them, then vacuum them in. They have few natural predators in the area, where they eat native fish and compete with them for food.

“They've pretty much colonized the entire Caribbean and Gulf of Mexico and up the East Coast of the U.S. up to about Cape Hatteras. But it's just about...