Jean-Dominique Marras, professional sea urchin fisherman in Corsica for more than 15 years, is experiencing his "worst season".

"All the elements went into it: bad weather, and in the little good weather, the sea urchins were empty. There are far fewer. But it's not just overfishing, there is certainly a problem of reproduction," he told AFP, wondering about a possible problem of "water temperature or pollution".

So certainly, "on the scale of Corsica, we are not moving towards an extinction of the sea urchin population," reassures Sonia Ternengo, of the scientific platform Stella Mare, in Biguglia (Haute-Corse): "But places have been very poached," she accuses.

This decrease in the resource is observed throughout the French Mediterranean, since 2017: towards Marseille, "densities have fallen to 1.5 sea urchins per m2 against 2 to 2.5 / m2 previously," says Marie Bravo-Monin, director of the Côte Bleue Marine Park.

Along this coast, between Marseille and Martigues, the traditional "sea urchins", where tons of "sea chestnuts" are swallowed on the go every winter, take a funny turn: most sea urchins now come from Galicia (Spain) or elsewhere.

"When you lift the stones, you see two or three small ones, before there were 30. The birth is done, but not in quantity, "confirms William Tillet, skipper-fisherman in Martigues.

A sea urchin fisherman at work at the bottom of the water near the Sanguinaires Islands, off Ajaccio, January 26, 2022 © Pascal POCHARD-CASABIANCA / AFP/Archives

"There are several causes, but it's mainly overfishing, even if fishermen don't like it," says Ternengo, whose team has managed to control sea urchin reproduction in the laboratory.

Fallow land in Cap Corse

In 2021, an amateur fisherman was found with 985 sea urchins on the Blue Coast, probably to sell them to restaurateurs, while he was only entitled to four dozen per day.

But other factors, such as the modification of plankton, which impacts sea urchin larvae, are also advanced. In Marseille, paradoxically, it is the improvement in water quality that would have eliminated high concentrations of sea urchins, which fed on discharged wastewater, lists Ms. Bravo-Monin.

Finally, there would be the increase in water temperature.

According to a study by Australia's Curtin University, the warming of the Indian Ocean has led to the disappearance of a large number of invertebrates such as molluscs and sea urchins present on Rottnest Island, 20 km off Perth.

However, in the summer of 2022, the western Mediterranean experienced a marine heat wave, with peaks at 28-30 degrees. This could eventually change the fauna and flora, according to Karina Von Schuckmann, German oceanographer with Mercator Ocean International.

Faced with this scarcity of sea urchins, whose harvest is only authorized from December 15 to April 15, and which take four years to reach an edible size, Corsican professionals are even considering "closing fishing for two or three years," reports Xavier D'Orazio, a fisherman in Ajaccio. But on condition that this decision emanates from the State, he stresses, so that the fishermen are compensated.

Sea urchins for sale at the fish market in Ajaccio, March 25, 2023 © Pascal POCHARD-CASABIANCA / AFP

In the Cap Corse Marine Natural Park, "four fallow areas" have already been set up since November, for three years.

If Sonia Ternengo is not against a closure of the fishery, she recalls that "Stella Mare is working on sea urchin releases (...), not to reach this extreme".

Provençal fishermen are discussing "a three-year moratorium on sea urchin fishing, but opinions are far from unanimous," says Pierre Motta, at the Interregional Directorate of the Mediterranean.

You have to be "sure that it works," confirms William Pillet in Martigues. Quotas, shortening the fishing calendar, all options are on the table.

The Scientific Council of the Côte Bleue Marine Park leans towards specific fallow areas, but over longer periods. On the model of those set up for red coral.

© 2023 AFP