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The Big Seashell Survey

Recreation Pollution Long-term data monitoring Climate change

Before the Big Seashell Survey started, there was little quantitative information on the species and numbers of shells that wash ashore at the Belgian coast. However, beached shells can say a great deal about climate change, environmental pollution, impact of human activities at sea and changes in biodiversity.

"What species of shell are common or rare, and how do they relate in terms of relative abundance? What about exotic species? Are there differences between the West and the East coast? And what species may be crowned as the absolute topdog?"

Big Seashell Survey

Big Seashell Survey

The Big Seashell Survey is a unique citizen science initiative on Belgian beaches. It is organised by the Flanders Marine Institute (VLIZ), EOS, Natuurpunt, the Province of West Flanders, the Strandwerkgroep, Kustererfgoed and the ten coastal municipalities.


Citizens active during the Big Shell Survey, help researchers in collecting and identifying massive numbers of shells (140,000 shells during four editions) and thereby examining patterns in biodiversity of shells along the Belgian coast. In addition, it contributes to ocean literacy and environmental awareness among citizens.


One day in March every year, citizens go to the beach and collect, count and identify shells according to a fixed scientific method.

Each participant collects a hundred shells and identifies the species involved with the help of the experts and a shell identification card, a field guide or the digital app ObsIdentify. After a quality check by the experts, the data are transferred to a database where it is further processed.

people collecting sea shells

Used components of the LifeWatch Infrastructure

The training sessions provided under the LifeWatch program, allow citizens to become ‘experts’ in identification of seashells. This new community of engaged citizens is an important asset for further biodiversity research along the Belgian coast.

Seashells in a tray


News and outreach

  • 2021, Baltic tellin most common bivalve at the fourth Belgian Big Seashell Survey
  • 2020, Big Shell Counting Day 2020 investigates effect of winter storms on composition shells Belgian beaches
  • 2019, Subtruncate surf clam and common cockle most numerous on Big Shell Counting Day 2019
  • 2019, What will the second Big Shell Counting Day of 16 March bring? 
  • 2018, More than 30.000 shells identified on first BIg Shell Counting Day in Belgium
  • 2018, Citizen scientists examine shells on the Flemish beaches 



Jan Seys

Spokesperson/Department Head Communication VLIZ

Tel.: +32-(0)59-34 21 40


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