For this sixth edition, Natascha and her children draw a large spiral in the sand. Armed with plastic buckets, they collect the shells inside their drawing before bringing them back to the beach, where they are carefully sorted by volunteers, then counted and recorded by species.

"We have to collect all the shells that are not broken," says Natascha Perales, 40, who is participating in this initiative for the first time. "We found mussels, oysters, cockles... At least six different species. It's a great activity despite the weather," she smiles.

The gusts of wind did not discourage the ten participants who took turns at the stand in Middelkerke (northern Belgium). Laurence Virolée, 41, came with her three children: "We learned a lot of things. Last year, we had already participated in a beach clean-up day. It is important for children to see the evolution of biodiversity and to raise their awareness of climate facts."

Volunteers sort shells they have collected on a beach in Middelkerke, Belgium, March 25, 2023 © Kenzo TRIBOUILLARD / AFP

Around 800 shellfish counters took part in the operation, which took place simultaneously in Belgium, the Netherlands and, for the first time, in France.

- Alien species -

In total, some 38,000 shellfish were counted, about the same number as in 2022.

"Shellfish are a good indicator of the state of biodiversity in the North Sea," says Jan Seys of the Flemish Institute of the Sea (VLIZ), organiser of the annual event.

A volunteer observes under a microscope a shell collected from a beach in Middelkerke, Belgium, March 25, 2023 © Kenzo TRIBOUILLARD / AFP

"Last year, 15% of the shells found belonged to exotic species" - particularly monitored by scientists who fear they are invasive. "For example, we have seen American species appear on our coasts," such as the American knife, says Jan Seys.

At the edge of the beach Joris Hooze, 75, offers participants the opportunity to observe mollusks under a microscope and learn to distinguish their peculiarities.

A retired biologist, he is part of a Belgian association dedicated to the observation of marine biology. "It has been observed that organisms normally living in warm waters are appearing more and more on the coast," he explains. For him, "it is a sign of climate change".

At the beginning of March, the European Union pledged more than €800 million to protect the oceans.

Volunteers collect shells on a beach in Middelkerke, Belgium, March 25, 2023 © Kenzo TRIBOUILLARD / AFP

"Europe wants to restore our oceans by 2030. If we want to achieve this goal, we need the public. And this type of initiative helps to raise awareness of these issues," comments Jan Seys.

This year, shellfish with holes were the focus of attention for scientists who want to determine how many predatory snails threaten shells.

© 2023 AFP