In the 1976-1986 period
Atylus swammerdami was observed across the entire Belgian part of the North Sea with a low distribution frequency and in low densities (up to 60 ind./m2). A similar distribution pattern was also found in the 1994-2001 period. The most remarkable difference was the high distribution frequency near the southern Zeeland Banks. This is where the highest densities were observed (up to 170 ind./m2).