A deep-sea expedition last month found that Atlantic Ocean lionfish are moving into the Atlantic coast in large numbers. Even more disturbing for researchers was the fact that the lionfish found during the expedition were large, meaning they can more easily reproduce and travel to varying depths.

The expedition was the first to use a deep-sea diving submersible to examine lionfish populations in the Atlantic. Reseachers dove to depths of over 300 feet off the coast of Fr. Lauderdale, Florida to find lionfish near a cargo ship that was intentionally sunk to create an artificial reef.

“We expected some populations of lionfish at that depth, but their numbers and size were a surprise,” said Stephanie Green, a researcher at Oregon State University who participated in the research. “This was kind of an ‘Ah hah!’ moment. It was immediately clear that this is a new frontier in the lionfish crisis, and that something is going to have to be done about it. Seeing it up-close really brought home the nature of the problem.”

The expedition’s findings have raised new alarms for collaborative efforts to control the lionfish population on the Atlantic coast due to the fish’s destructive predatory behavior. Lionfish, which are native to the Pacific Ocean, were accidentally introduced into the Atlantic in the 1990s. The fish have no natural controls on their populations in the Atlantic, and previous studies have shown lionfish can reduce native fish populations by as much as 80%.

“A lionfish will eat almost any fish smaller than it is,” said Green. “Regarding the large fish we observed in the submersible dives, a real concern is that they could migrate to shallower depths as well and eat many of the fish there. And the control measures we’re using at shallower depths – catch them and let people eat them – are not as practical at great depth.”

(Image courtesy Oregon State University)