Venomous Lionfish Invade the Mediterranean

A recent survey shows that the fish have colonized Cyprus and may continue to spread

Maria Papinikola

In a recent survey of divers and fishermen in Cyprus, researchers discovered that the invasive lionfish have colonized the eastern and southern shores of the island. Scientists worry that this advance could threaten the biodiversity of the entire Mediterranean.

The survey, published this week in Marine Biodiversity Records, identified at least 19 lionfish along the coast, some of which showed mating behavior.

The fish, Pterois miles, can grow up to 18 inches long, weighs around two pounds and has 18 venomous spines. ​It's a native of the Pacific and Indian Ocean, where natural predators keep them in check. But when the fish escape into waters outside of this range, the lack of natural predators means the invasives destroy populations of local creatures.

According to Aidan Quigley at The Christian Science Monitorthe lionfish chows down on the fish that normally munch on algae. Without this natural janitor, the algae and seaweed will build up, smothering coral reefs to death. Lionfish spawn every four days year-round, releasing up to 2 million eggs per year, which float great distances on the ocean surface.

The fish has already destroyed parts of the Caribbean, where many aquarium owners release them into the wild. In one study, lionfish reduced reef fish by 65 percent in just two years.


Lionfish are also found in Florida. The fish first appeared there in the 1980s, but the population exploded after 2007, reports David Martin at AlJazeera America. The Florida lionfish now threaten populations of commercial fish like grouper and snapper. The state encourages divers to collect the fish, which do not fear humans, and has also begun an outreach effort to encourage people to eat the predator.

Even so, most efforts to control lionfish in the Western Hemisphere have failed. So halting the Mediterranean invasion is critical.

“This is the first scientific proof that they are invading, but we don’t know what the ecologic impact will be,” Jason Hall-Spencer, an author of the study and marine biologist at Plymouth University tells Quigley. “What would be best is to stop it now, instead of waiting to see what the environmental effects are.”

The researchers believe that two main factors led to the lionfish invasion. First, as the climate changes, the cold waters of the Mediterranean Sea have warmed enough to become attractive to the fish. Second, an expansion and deepening of the Suez Canal was completed last year. This change eliminated salty regions of the channel that prevented the fish from crossing. “With more flushing of water going through, it’s more conducive to the spread of invasive species,” Hall-Spencer tells Quigley.

In the press release, Hall-Spencer suggests that immediate action needs to be taken over the next month to control the fish, such as encouraging divers to spear them. Longer-term solutions could also include introducing natural predators like the dusky grouper.

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