Lionfish invasion comes to the Mediterranean

Lionfish are beautiful in aquariums, but they are a menace in the waters of the western Atlantic. Armed with venom and a reproductive ability that lets a single fish produce 2 million eggs each year, the fish have managed to establish themselves in ocean waters from Florida to South America and throughout much of the Gulf of Mexico. In the decade or so since the fish were purposely or accidentally released into these waters, which are far outside their native range in the western Pacific, they’ve becoming the dominant predator on many coral reefs.

In the Mediterranean, though, lionfish have occasionally been spotted, but the region has seen nothing like the fast spread of the fish in the Atlantic. One lionfish was spotted in Israel in 1991, but the next two weren’t sighted for more than two decades, when they were captured off Lebanon in 2012. But in recent years, more and more of the fish have been found in the waters off Turkey, Cyprus and Greece.

Some scientists had thought that even if the fish accidentally made their way into the Mediterranean — the Suez Canal provides an easy route from the Red Sea, where the fish are native — the waters would be too cold for lionfish to settle there. But a new study finds that’s not the case. Lionfish are now found along nearly the entire southeastern coast of Cyprus, and they’re exhibiting mating behaviors, researchers report June 28 in Marine Biodiversity Records.

Demetris Kletou and colleagues at Plymouth University in England and the Marine and Environmental Research Lab in Limassol, Cyprus, collected reports of lionfish sightings that showed up on social media and among networks of fishermen and divers in Cyprus in 2015. They then mapped the distribution of lionfish using more specific information from divers and fishermen who had seen the fish.

There weren’t a lot of lionfish in the reports, just 19 fish that had been spotted a total of 24 times (the fish can be distinguished by their pattern of stripes). But the fish had been seen across a wide area of southern Cyprus in a single year. And they also found evidence that the solitary fish were pairing up to mate.

“It appears that the lionfish have found their niche, formed reproductive populations and are now established,” the researchers write.

Catching the invasion early on, though, could give managers time to halt it in its tracks. Targeted removal of fish by divers has had some success in the Atlantic, and this might also be a good strategy in the Mediterranean. It’s also possible that native fish could keep the lionfish population under control, though that obviously hasn’t worked in the Atlantic.

But the big worry is how climate change will affect the Mediterranean. If large parts of the great sea are currently inhospitable to lionfish because the water is too cold, then it could soon open up as the oceans continue to warm.