Composition and structure of the seabed

Immediately following mussel seed fishing, the composition of the seabed changes at some locations, but not at others. This seabed temporarily shows a significant decline of structure as a result of the fishing.

The seabed composition is based on grain size and silt fraction. Samples were taken with the box core, which showed large differences between the locations and in time. In sandier areas, a significant difference was found in the silt fraction of open and closed sections immediately after fishing. In the closed sections, the silt fractions were somewhat higher because the mussels filter the silt from the water and deposit it on the seabed.

The seabed structure was mapped out using side scan sonar recordings and a processing program for spatial patterns. A positive association was found between the parameter that was used (Moran’s I) and the mussel biomass. Statistical analysis showed a significant decline in structure as a result of, and immediately following, the fishery. This difference was no longer apparent after 1 and 2 years.