Dangerous Encounters: What Globetrotters Need to Know

The Mediterranean is changing. As water temperatures rise, invasive fish species are spreading further west. Two species, in particular, are causing great concern among scientists, fishermen, and conservationists: the highly toxic silver-cheeked toadfish (*Lagocephalus sceleratus*) and the red lionfish (*Pterois miles*). Both are native to the Indian Ocean and entered the Mediterranean via the Suez Canal.

The silver-cheeked toadfish is currently considered the greater threat. It has already spread extensively in the waters off Greece, Cyprus, and Turkey, and is increasingly being detected in the central and western Mediterranean as well. With its powerful teeth, it destroys fishing nets, devours trapped fish, and displaces native species. Particularly dangerous, however, is its neurotoxin tetrodotoxin (TTX)—one of the most potent natural toxins known. Even small amounts can be fatal to humans. Consequently, this fish must under no circumstances be eaten.

To curb the spread, Greek authorities are now paying fishermen a bounty for every pufferfish caught. The goal is to bring the population under control, at least to some extent.

The red lionfish is also spreading rapidly. Its striking red-and-white stripes and long fins are spectacular, yet its dorsal spines contain a painful venom. As a highly successful predator, it consumes large quantities of small fish, thereby threatening the ecological balance of many coastal regions. Unlike the pufferfish, however, its flesh is edible once the venomous spines have been properly removed and is even considered a delicacy. Consequently, some Mediterranean countries are making concerted efforts to establish the red lionfish as a food fish.

To date, neither species is a common sight around Mallorca. However, as the Mediterranean continues to warm, marine biologists anticipate that the red lionfish in particular—and the silver-cheeked toadfish in the long term—could be spotted more frequently in the Balearic Islands.

Tips for swimmers and snorkelers

• Never touch unfamiliar fish with bare hands.
• When snorkeling, keep a safe distance from conspicuously striped or spherical fish.
• If you spot a red lionfish, avoid any contact with its spines.
• Under no circumstances should you catch a rabbit-headed pufferfish or keep it as a food fish.
• Photograph unusual sightings and report them—if possible—to local authorities or marine research projects.

There is currently no cause for concern for water sports enthusiasts. Encounters with these species remain rare, and the animals do not actively attack humans. Nevertheless, it pays to keep a watchful eye—for the Mediterranean is undergoing change, and its underwater world is shifting along with it.

Other invasive fish in European freshwaters

• Black-mouthed gobyThis small fish from the Black Sea region has proliferated extensively via canals in almost all major Central European rivers (such as the Rhine and the Danube) as well as in the Baltic Sea, displacing native bottom-dwelling fish.
• Sunfish: Originally from North America, it is spreading in many European lakes and ponds.