How an invasive fish is threatening the Mediterranean Sea

An invasive lionfish species found in the Mediterranean Sea could threaten the region's ecology if not addressed immediately, scientists say.  

Researchers from Plymouth University in Britain found that the venomous predators had colonized the coast of Cyprus, prompted by rising sea temperatures and the widening and deepening of the Suez Canal.

Jason Hall-Spencer, a professor of marine biology at the University of Plymouth, tells The Christian Science Monitor that study co-author Demetris Kletou discovered that the lionfish were invading the waters near Cyprus, an alarming discovery. 

"This is the first scientific proof that they are invading, but we don’t know what the ecologic impact will be," Professor Hall-Spencer says. "What would be best is to stop it now, instead of waiting to see what the environmental effects are."

The study notes that few sightings of the alien lionfish Pterois miles have been reported in the Mediterranean. The study authors found and identified at least 23 specimens, some of which exhibited the first lionfish mating behavior ever seen in the Mediterranean. 

Hall-Spencer says the Mediterranean was previously believed to have been too cold for the species to survive. But rising sea temperatures caused by manmade climate change have made the sea livable for the lionfish, he says. The deepening and widening of the Suez Canal has also played a role, as previously the canal had high salt areas that stopped the transport of species, he says. 

"With more flushing of water going through, it's more conducive to the spread of invasive species," he says. 

An earlier lionfish invasion had a major effect on the Caribbean, which is heightening concerns about the Mediterranean. The carnivorous lionfish eat the small native herbivorous fish that keep algae and seaweed levels under control. Hall-Spencer says that in the Caribbean, lionfish devastated the population of herbivorous fish, which in turn led to unprecedented growth of seaweed, killing the coral reefs. 

The lionfish population boom in the Caribbean coincided with a 65 percent decline in native fish populations over the course of two years, research shows. 

They had no natural predators in the Caribbean – nor do they in the Mediterranean, says Hall-Spencer.

"Large predators of the Mediterranean have been overfished," he says. "Groupers would be capable of taking out a lionfish, but they’re mostly gone." 

Hall-Spencer says only immediate action can address the problem. He also encourages diving groups and fishermen to capture and eat the fish, which he describes as "quite tasty."

Scientists also encouraged the consumption of lionfish to address the problem in the Caribbean, as the Monitor reported. The fish have venomous fins, but are completely safe to eat once the fins are removed. Capturing the fish, however, can be time-consuming, as they cannot be caught on a line but must be netted or speared, the Monitor reported. 

The difference between the Caribbean and the Mediterranean invasions, Hall-Spencer says, is that in the Mediterranean, we still have a chance to rid the area of the lionfish. In the Caribbean, he says, the population has grown to large to control. But with only a couple dozen lionfish spotted near Cyprus, the population may be small enough to eliminate before the problem increases. 

“If there's a concerted effort made now, over the next month or so, we could probably stop this environmental problem from getting out of control,” he says.