Baltic Sea: technological innovations in mussel dredging

The effects of dredging blue mussels, Mytilus edulis are not only the physical removal of structural musselbeds and resuspension of sediment, but also the removal of water filtration capacity, all of which impact the ecosystem. The present study demonstrates that fishing impacts can be reduced through gear developments based on stakeholder involvement.

We developed a new Light Dredge and tested it against a standard dredge on commercial vessels using different experimental setups. The development and test part was already done before BENTHIS started as part of other projects. But the analysis had not been done yet. Results from the experimental fisheries demonstrate that the weight of sediment retained and resuspension of sediment at the surface is less in the Light Dredge. Also, the drag resistance was significantly lower indicating a reduction in energy transfer to the sediment, whereas catch efficiency was increased. Sea floor tracks made by the two dredges could not be distinguished by use of a side-scan sonar and the tracks were still detectable two months after fishing.

The experiment was successful. In comparison with a standard dredge, the Light Dredge can reduce the impact on the ecosystem by reducing resuspension of sediment, reducing area of impact through an increase in catch efficiency, and by reducing fuel consumption and energy transfer to the sediment through a reduced gear drag resistance.