August 4, 2020

The blue crab takes the Delta del Ebro | Society


"Now we only catch blue crab, what are you going to do in the face of this explosion? That's what it is, if last year we took 15 kilos a day now they are between 200 and 300 kilos, "explains Ivan Samper, patron of the Saron, while driving towards the monetas (traps for crustaceans) waiting for patients in the waters of the Ebro Delta bay. The blue crab (Callinectes sapidus), indigenous to the Western Atlantic from Nova Scotia, Maine and northern Massachusetts to Argentina including Bermuda and the Antilles, was first detected in the area in 2012, although it was already in Italy, Turkey or Greece. Now the Delta del Ebro is infested and the species, which lives in estuaries and lagoons, moves towards new coasts.

While the Saron rocks in the calm waters, the crabs, trapped in the pots and with no possibility of escape, fill large plastic baskets, helped by the sailor Salvador Moreso who warns: "Be careful, if they catch you, they will not let you go and do hurt". The size of the claws of the impressive crustacean, with tips of an intense blue in the males and red in the females, leaves no doubt. The length of its carapace can reach 24 centimeters and there are copies of a kilo.

EVOLUTION OF THE PRESENCE OF THE BLUE CRAB IN THE EBRO DELTA

Growth in the last five years

Source: Department of Agriculture, Livestock, Fisheries and Food of the Generalitat of Catalonia. Photography: Josep Lluís Sellart and Massimiliano Minocri.

The voracious crab feeds mainly on shellfish bivalves – you can eat 575 clams a day in an unprotected shellfish bank – in addition to annelids, fish, plants and almost any other element you can find, even individuals of the same species. Its only natural predator is the octopus, "and there are not enough to kill them", ironically Samper. Only man remains, "but it is necessary to reach a good price in the market, as in the United States." Last week it oscillated between three and 0.70 euros per kilo in the fish market of Sant Carles de la Ràpita, from where the crab is sold, which "makes good broth for rice" and makes its way into the kitchens of renowned chefs.

Joan Balaguer, secretary of the fishing brotherhood of Sant Carles, indicates that they capture an average of 1,000 kilos per day. "Last year we reached 60 tons and, this year, in two months we are at 37, which gives an insight into how the species has grown," he says. Nothing strange, if one takes into account that in each laying the females release between two and eight million eggs, and that they live in fresh and salt water, points out Pere Abelló, researcher at the Institute of Marine Sciences in Barcelona of the Superior Council of Scientific Investigations (CSIC). "Fishing is encouraged to try to keep it at bay, because eradicating it is already impossible," he warns. The Generalitat has promoted a management plan for the species and has created a management committee involving fishermen and shellfish gatherers, scientists and ecologists.

Vicent Moya, a fisherman in Sant Carles since he was 14 years old, now faces, with 52, the change of course that the crustacean has imposed on him. "The cockles, the clams and the green crab have disappeared, the one here, although the knife still holds," he says. A situation that has pushed him, like the rest, to opt for the new tenant. Moya wonders how it will affect the octopus, sepia … With this background, the species is included in the 100 most invasive of the Mediterranean, although still does not appear in the catalog of invasive alien species in Spain. The Ministry for the Ecological Transition has initiated the procedure and is awaiting the opinion of the Scientific Committee. The Generalitat, for its part, has a management plan and has created a committee in which fishermen, shellfish gatherers, scientists and ecologists participate.

BLUE CRAB (Callinectes sapidus)

Characteristics and year of detection in the Spanish Mediterranean

Source: Department of Agriculture, Livestock, Fisheries and Food of the Generalitat of Catalonia. Photography: Josep Lluís Sellart and Massimiliano Minocri.

The fear of damage caused by the plague is palpable among fish farmers. Jesús Carles, a family dedicated to the cultivation of mussels and other molluscs for "at least 56 years", shows from a boat the 120,000 square meters of plot for the cultivation of the Japanese clam in the bay of Fangar (in the Ebro Delta ), now occupied only by ducks. "Last year the crabs ate them all, and we can not put protection because they are raised on the ground," he explains. The exploitation, the only one of this type that existed in the Delta, produced 80,000 kilos per year "and there was a great potential to expand the crop."

At the moment the mussel has been freed. "But we have the creeps, waiting for the summer to come when there is more crab," says Gerardo Bonet, manager of the Federation of Shellfish Producers of the Ebro Delta (Fepromodel). In the rafts of the two bays (Fangar and Alfacs), four million kilos of mussels and 400,000 of oysters are produced. The aquaculturist continues the march through the bay and approaches one of the breeding rafts. On one of the ropes, a blue crab is giving a good account of the mussels. "They break the shell without problems", shows Carles.

The arthropod continues its relentless march along the coast and has already reached the Mar Menor or the Albufera natural park in Valencia. In the summer of last year, the first specimens were confirmed in the Guadalquivir Bay and in Mallorca and Menorca. "The disconcerting thing is that when it is established it adapts to any situation", explains Carmen Barberá, researcher at the Center for Marine Research (CIMAR) at the University of Alicante. The scientists are collaborating with the fishermen. Diego Amorós, president of the Fishermen's Association of Guardamar del Segura, has it clear: "Either we stop it or it gets out of hand". "Here we are dedicated to shrimp fishing and we destroy the networks, so we try to run away," he says.

Miguel Vivas, a researcher at the Spanish Oceanography Institute that monitors the species in the Mar Menor, maintains that "it is here to stay, unless it is infected by a plague or another health problem that may affect it." He is also concerned about the impact he may have on the seahorse. "It's a species that has all the ballots to lose, we already have proof that it feeds on them." While scientists and public administration try to stop an invader that overwhelms them, the fisherman Ivan Samper counts the days to focus on the high seas and leave behind the crab that threatens its environment.

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