Subtruncate surf clam and common cockle most numerous on Big Shell Counting Day 2019 | Flanders Marine Institute

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Subtruncate surf clam and common cockle most numerous on Big Shell Counting Day 2019

Oostende (2019.03.19) – On Saturday 16 March, the 800 participants to the Big Shell Counting Day all together collected 53,644 shells in ten coastal municipalities along the Belgian coast. Crackers were the Subtruncate surf clam and the Common cockle, each present with approximately 14.000 specimens each. A relatively high percentage of fossil shell material was encountered though, due to the strong onshore wind of the past week preventing fresh shell materials to wash ashore.

Press release by: Flanders Marine Institute (VLIZ)

Almost 60% of all shells found was fossil material (in 2018: 47%). These shells are a remain, among other things, of the coastal habitat that occurred along our coast in the past seven thousand years ago and was rich in mud flats. The majority of all shells of the top 2 – the Subtruncate surf clam and the Common cockle – were fossil specimens. The higher numbers of the European flat oyster, the Peppery furrow shell and the Truncate softshell clam are also testimony to this past.

Due to the persistent hard W-SW winds over the past week, little or no new shell material was washed ashore. The stormy weather caused an offshore undercurrent moving those shells that were washed from the seabed in a seaward direction, instead of towards the coast. The strong wind also covered the flood marks on the beaches with blown away sand, making it particularly difficult to trace small shells. See the lower numbers of the Baltic macoma, the Atlantic jackknife clam, the Netted dog whelk, the bean-like tellin and the Milky-white ark shells encountered.

The set target to collect 100.000 shells proved to be too ambitious, due to the poor weather conditions last Saturday. Yet the 800 participants (in 2018: 400) succeeded in taking an impressive "sample" of our shell fauna. With the help of 80 shell experts, 53.644 shells (in 2018: 30,200), belonging to 57 species, were counted.

Again, clear differences could be detected between the eastern and western Belgian coast. More prominent on the West Coast were the Atlantic jackknife clam, the Solid surf clam, the Pullet carpet shell and the Bean-like tellin. The Baltic macoma, on the other hand, was noticeably less numerous on the West Coast.

With almost 10% of all shells found having an "exotic" origin (the Atlantic jackknife clam, the American piddock, the Pacific oyster, the Common slipper shell, the Manila clam), it has been confirmed how much our fauna has changed over the past century through human intervention.

The Big Shell Counting Day is an initiative of the Flanders Marine Institute (VLIZ), Natuurpunt, EOS, the coastal heritage center (Kusterfgoed), the Province of West Flanders and the natural history association Strandwerkgroep, with the active support from the ten Belgian coastal municipalities ( - in Dutch only). With this initiative, all partners want citizen to get more involved into coastal research. After all, collecting and recognizing shells is not only fun or interesting. The data collected by this citizen science initiative also gives the marine researchers new information about the occurrence of this group of marine animals along the Belgian coast.


Additional visual materials are available on request.

Press contact

Jan Seys, co-ordinator Big Shell Counting Day - Spokesmen VLIZ
+32-(0)478-37 64 13 |