Wednesday, December 1

Despair in the French Mediterranean over the invasion of blue crab crab

“A war machine”. This is, in essence, the conclusion that one draws when reading the characteristics of the Callinectes sapidus “, better known as the blue crab. This crustacean, native to the Atlantic coast of the United States, from Canada to Argentina, has packed its bags to colonize other The problem is that this species is especially invasive and its presence, when it proliferates, threatens the balance of existing ecosystems.

In France, eel fishermen in the Canet pond, in the southern department of the Pyrenees-Orientales, are experiencing it bitterly. “It disgusts me,” says Jean-Claude Pons, standing in his little boat, lifting his nets overflowing with blue crabs, which could spell the end of the eels he has been fishing here for 40 years.

In all likelihood, this especially aggressive and voracious species arrived in Europe in the holds of ships, when they were emptying ballast water. The presence of this crab, which owes its name to its blue claws, had already been observed in the Mediterranean for several years, especially in Spain, in the Ebro delta, or in Albania.

In the Canet pond, which is actually a lagoon watered by the water of the Mediterranean Sea, the first reports date back to 2017. But since then, as in almost all areas where some specimens had been observed, there has been an explosion . To understand the magnitude of the phenomenon, Jean-Claude Pons is catching between 500 and 2,000 blue crabs a day in August 2021, compared to one fish a day in 2018!

The king of crustaceans?

With its claws, the blue crab can cut through fishermen’s nets and even a finger if you’re not careful. As an adult, it can grow up to 25 cm and weigh almost a kilo. It is also an excellent swimmer thanks to its last pair of webbed feet. They can swim up to 15 kilometers a day. And what about their reproductive capabilities? Each female can lay more than 2 million eggs during the summer breeding season.

Omnivore, this crustacean feeds on all kinds of species: small fish, mollusks, amphibians, insects, and even small birds when it can catch them. It can live in temperatures ranging from 3 ° to 35 °, but its aggressiveness increases above 15 °. Also cannibalistic, the blue crab does not hesitate to pounce on its congeners to satisfy its hunger.

Lagoons and estuaries are the preferred environments for blue crabs, with a maximum depth of 35 meters. In this sense, the Canet pond meets all the requirements. If at present, the presence of the crab, en masse, is only located in this area, other sectors with similar characteristics are already worrying.

Not far from there, the oyster and mussel farmers of the Etang de Leucate and those of the Etang de Thau fear for their crops. The blue crab can feed on oysters and mussels. Thus, it could shake an entire economic fabric. Faced with this threat, the response is already being organized, especially with the placement of traps to catch them. Unlike in the United States, its predators, mainly the octopus, are not numerous enough to stop its expansion.

How to fight it?

To try to limit its proliferation, the French authorities have launched a surveillance campaign in the Gulf of Lion. But the solution may be in the food we eat. If we stick to the etymology of the crab’s name, “sapidus” -in Latin- means tasty. In the United States, crab is a famous dish, especially in the state of Maryland.

France could take an example from Tunisia, where another blue crab, the “Portunus segnis”, native to the Indo-Pacific region, has also wreaked havoc. Like its American cousin, this crab is especially invasive there too.

So much so that local fishermen have dubbed it “Daesh”, or Islamic State. But like its American cousin, it is also especially tasty. Therefore, a distribution chain has been established, not without difficulties. Marketing it is the only solution they have found in the other places where invasive blue crab species have appeared, such as the Ebro Delta or Albania.

Will the blue claw crab ever become the gold claw crab?

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