Erosion Threatens Oyster Farming in Cap-Ferret
The oyster farmers and residents of Cap-Ferret are concerned about the consequences of erosion in the Mimbeau pit, one of the most productive areas of the Arcachon Bay for oyster farming. Faced with repeated warnings, a study was commissioned by the State and the municipality, who had contacted the Observatoire de la Côte Nouvelle Aquitaine. The study was conducted by the Bureau de Recherches Géologiques et Minières (BRGM), and its results were unveiled on February 13th.
"The study findings show a change in the pit and the underwater slope that overhangs it, but do not indicate a sense of urgency in the regulatory sense," the Prefecture stated, without providing figures on the erosion at Mimbeau.
Benoît Bartherotte, president of the Pointe du Cap-Ferret defense association, disputes this conclusion. "They want us to believe that there is absolutely no risk or urgency at Mimbeau. The surveyors from the Syndicat Intercommunal du Bassin d’Arcachon (Siba) observed this worsening and measured it precisely in their report dated October 2nd. The comparison of the surveys from 2016 and 2024 shows, in a sector of the underwater slope, a retreat of 7 meters in 8 years, 5 of which occurred in the last year… So, without any possible equivocation, this is a worsening," he explained.
In this situation, the State proposes to allow oyster farmers to carry out work to reinforce the underwater dike they had erected to protect their parks and Mimbeau. Made of rocks under the sea, it has not been maintained for many years. "The State will provide technical and legal support to the professionals to design a protection project that will serve as a test. This project will be subject to an environmental assessment on a case-by-case basis. Its scientific relevance will be validated by a public institution. In addition, it has been agreed that this project will include a monitoring protocol," the prefecture explained.
"An 800-meter-long dike"
"We have already determined the dimensions of the structure we want to build. A dike 800 meters long, at the foot of our parks, at the edge of the channel to combat the erosion phenomenon. The State tells us that we will be able to start in the summer, and I hope this will be the case," said Olivier Laban, president of the Arcachon-Aquitaine regional shellfish farming committee. "There was a great deal of work with the State to try to find the right formula. Our goal has always been to protect the foot of our oyster parks. Since 2014, regulations no longer allowed us to protect them. We are moving in the right direction to be able to take action," he concluded.
According to a report by the Observatoire du Littoral published last summer, half of the region’s dune coastline was affected by erosion during the winter of 2023-2024. In Gironde, Lège-Cap-Ferret is one of the most impacted municipalities.
Last summer, Benoît Bartherotte and the associations of the owners of the 44 hectares raised the alarm. They relied on the annual bathymetric survey commissioned by Siba and prepared by surveyors from the Parallèle 45 firm. This data, in particular, reported a loss of 16,000 m³ of land on three areas "to be monitored."
