Toxic alert on mussels in the Thau pond: “a natural phenomenon, not pollution”, reassure shellfish farmers

Toxic alert on mussels in the Thau pond: “a natural phenomenon, not pollution”, reassure shellfish farmers

The ban on consuming shellfish is linked to the presence of a natural microalgae of the dinophysis genus. Midi Libre – MiKAEL ANISSET

The Hérault prefecture suspended, Thursday June 20 and until further notice, fishing, marketing and consumption of mussels, clams and gastropods from the Thau pond. The Mediterranean Regional Shellfish Farming Committee wishes to reassure the population and reminds that Thau oysters are perfectly edible.

Since Thursday June 20, the prefect of Hérault has banned the fishing, marketing and consumption of mussels, clams and gastropods from the Thau pond. ;rsquo;ban on temporarily consuming these shellfish is linked to the presence of a natural microalgae (phytoplankton) of the genus dinophysis, in the waters of the ;pond, and consequently in the species that consume them.

The Mediterranean Regional Shellfish Culture Committee, a representative body of shellfish farmers in the Thau basin, announced this Friday that this microalgae develops naturally in tropical and temperate waters. She is "under close surveillance"because it can synthesize toxins likely to accumulate in certain shellfish and thus cause, with high consumption, digestive disorders.

"We will refer to the import mold"

"It’s a natural phenomenon, specifies Patrice Lafont, the president of the CRCM. We are not talking about pollution. In the marine environment, there are thousands of species of phytoplankton, it is the base of the food chain. Three are known to produce toxins. When the thresholds are exceeded, then there is a risk for consumption. Preventive measures are therefore taken. For us, it’s routine. Weekly samples are taken in all French shellfish farming areas (375). The Thau pond does not escape the rule of national surveillance. Everyone's priority is the health safety of shellfish and consumers."

Oysters from the pond are not affected

If the situation is "under control" and does not concern Thau oysters, this alert does not exist. is not without harming the image of the pond. "Many people conflate it with all shellfish, regrets Patrice Lafont. Fishing shellfish and farmed shellfish must be separated. For oysters, we had to explain for a long time why it was not necessary to stop their consumption when the mussels were affected by toxicity. Mussels filter four times more than oysters, so they accumulate toxins much more. This is normal! In this case, the results for oysters are significantly below the regulatory threshold. The analyzes continue, but the consumer can eat them with their eyes closed."

On the pond, six closures in four years due to dinophysis

Last year, France experienced 468 closures by the national Rephy network (Phytoplankton and phycotoxin observation and monitoring network), everything has been confused, out of the 375 French shellfish farming areas monitored. 49 occurred due to dinophysis.

In the Thau basin, over the last four years, dinophysis is responsible for one closure in May 2021, and two in 2022 (January and October ), two in 2023 (January and May) and therefore this one in 2024. The ban lasts on average around fifteen days.

"What worries us is that this natural microalgae was absent in the’ étang de Thau in the pasté, observes Patrice Lafont. She appears more and more. We don't see what favors it in our environment. Dinophysis is the species that causes the most shell closures. Ifremer is working on the subject but has not yet understood what favors its development (salinity, weather, temperature, etc.). erasures…)."

Nearly 450 companies around the Etang de Thau are affected by this ban on fishing and marketing of mussels, clams and gastropods. The alert comes at a bad time, since the mussel season was just beginning on the pond. "The mussel here is a native mussel. summer, from June to September, recalls the president of the CRCM. In warmer years, we can attack from the month of May. This ban will result in a shift in sales to imported molds, which is never pleasant. In Europe, we import mussels from Spain, but they are not really beautiful… hellip; We have no choice but to rely on this to satisfy customers. But, economically and in terms of image, it is not the best." Marketing will resume when two successive analyzes show results lower than the regulatory threshold for each of the shellfish concerned.

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