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“There’s some concern that the lionfish might be using a deep-sea refuge,” said Green, noting that further study is needed to confirm that hypothesis.
The effect of the lionfish, a venomous fish that plumes like a Japanese fan, is well known in the shallower Atlantic, but its impact on the deep sea is less well understood. The animal is what is known as a gape-limited predator, which means that the fish is limited in food consumption by the size of its mouths. The fish, growing up to 47 cm in length, can consume prey up to half its size, which puts about 70 percent of the fish population within their gulp. Studies have shown that at least 40 species of fish have dropped in number since the lionfish was introduced to their Atlantic environment, Green said.
“There is strong evidence that the lionfish is having negative effects on the native population,” she said. “We don’t see any signal that anything is controlling lionfish population.”
As big fish tend to live longer, the lionfish also reproduce more efficiently than do smaller fish: One female lionfish can spawn some 2 million eggs per year; the eggs are bundled in gelatinous blobs of some 12,000 to 15,000 eggs and distributed throughout the ocean. That means that the invasive lionfish population has grown in a disproportionate number relative to native fish deep in the Atlantic.
And a separate study released this week from the University of North Carolina at Chapel Hill also suggested that a lack of native predators in the Atlantic has further boosted the lionfish’s disproportionate growth: Nothing is down there to eat them.
Researchers are now investigating possible solutions to the lionfish problem, including creating deep-sea traps that could nab the large fish, said Green. Scientists are also hoping to catch one of the fish – using mounted suction cups – in the deep environment to better understand the changing ecosystem there.