Triggerfish, rabbitfish, Portuguese galleys… With water at 26°C from the month of July, the Mediterranean Sea is destined to shelter underwater species from tropical areas and to see others disappear. Upheavals in marine fauna that could have serious consequences for the Mediterranean ecosystem.
A very flat body, about forty centimeters long, with small teeth ready to bite the calves of overly curious vacationers: the triggerfish is one of those species that has been proliferating for several years in Mediterranean waters thanks to of a constantly increasing average temperature. Blame it on the remoteness of its natural predators such as tuna or shark, towards cooler waters, deeper and better stocked with food.
“Fish do not have a system for regulating body temperature, explains Bastien Henckel, technical manager at the Grau-du-Roi Seaquarium. When the water heats up, large predators such as tuna need to speed up their metabolism by feeding more. This leaves the field open to triggerfish, which extend their spawning area, multiplying the risk of encounters with humans during the breeding season, between June and August..
The Mediterranean in galley
And if the triggerfish is not a newcomer to the Mediterranean landscape, some species have only recently been observed in the big blue.
This is the case of the Portuguese galley, this cousin of the jellyfish usually present in tropical waters. The animal with iridescent reflections is equipped with a surface float filled with carbon dioxide, which offers a grip on the wind similar to the boats of Lusitano explorers. Below, a bag of tentacle nodes set with stinging cells microscopic sweeps the depths, reaching up to 50 meters in length. Cells that release a toxin through the skin causing nausea, vomiting, breathing difficulties and even malaise in about twenty minutes.
These tentacles, even when severed or washed up on beaches, continue to sting. “Specimens of Portuguese galley have been observed off the Sicilian coast, carried long distances by prevailing winds and currents”explains B. Henckel, reassuringly: “These are animals that do not have the ability to move spontaneously, so the risk of proliferation is low.” Here again, it is the gradual disappearance of the natural predator, the loggerhead turtles, which is at the origin of more frequent encounters with humans. In mid-July, the sting of a specimen is said to have caused the death of a woman in Sardinia.
Bastien Henckel is the technical specialist of the Seaquarium in Grau-du-Roi.
Species that are directly dangerous for humans, but also for the marine ecosystem. The rabbitfish, behind its harmless name, is a real threat to the Mediterranean floor. Fished for the first time in Lampedusa in 2013, the so-called puffer fish was traditionally present in the Red Sea. The large herbivore gradually reached the Mediterranean through the Suez Canal before colonizing the northern area of the Maghreb, ravaging the Posidonia meadows in its path.
A real drama for the submerged lungs of the planet, whose posidonia absorbs 15 times more CO2 than the Amazonian forest. “The rabbitfish is a real problem because by destroying the underwater flora, it causes damage to the entire ecosystem. And the technical manager concludes: Unfortunately, there is not much to do because eradication would be difficult to achieve.”
Watch out for the calves!
During the winter, the triggerfish can live up to 100 meters deep. When summer arrives, it goes in search of warmer areas to create its nest there for the breeding season.
From June to August, the females will come to lay their eggs in areas 30 to 5 meters deep, in the sand in an open area. And as the species proliferates, spawning takes place closer and closer to beaches. It is therefore to protect the eggs that the male goes on the hunt for calves, defending the plot of his offspring at all costs.
And despite its relatively small size, the bites of the animal are not to be neglected. Because beyond the bite itself, there is a risk of infection. Given the flesh residues present in the mouth of the predator, it is advisable to disinfect the bitten area with care. So if you have the unpleasant experience, go to a first aid station as soon as possible, even if the bite is only superficial.