External Organisations

  • Faaborg Recreational Fishery Association, Denmark
  • University of Southern Denmark, Denmark
  • Nordshell IS, Denmark

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The aim of the project is to improve fish habitats and fish populations in Nørrefjord by restoring blue mussel reefs in the fjord. This is based on the assumption that blue mussel reefs will provide complex habitats for fish, and improve the conditions and availability of prey organisms and hiding places for both juvenile and adult fish in the fjord. The mussel reefs may have additional beneficial effects, such as improved water visibility above and around the reefs due to the large filtration capacity of the mussels. Increased water visibility may also improve the growth conditions of the sea grass (Zostera marina) beds in the area.

Blue mussels (~ 40 ton) have been produced on ropes in the fjord from the indigenous mussel larvae stock in 2 years, 2010 and 2011. Harvested mussels were distributed on sandy-muddy seabed in a study area in the southern part of the fjord mainly by use of volunteer, local fishermen. The mussel reefs were laid out as small patches (3 meters in diameter) with 5 to 7 meters in between to increase the complexity of the fjord substrate. This design mimics the observed distribution of existing mussel beds in the fjord. Different approaches for production of the mussels and deployment of the reefs have been investigated to minimize costs, manpower and time use.

A scientific monitoring program has monitored the distribution of fish populations and prey organisms in the study area and a control area in 2010 and 2011, before and after the restoration of the mussel reefs in the study area. Furthermore, water visibility and the distribution and condition of the sea grass beds in the area have been monitored. Samples and results are being worked up at the moment. Preliminary results show surprisingly healthy sea grass beds in both the study and control area, indicating that the environmental conditions in this highly eutrophicated fjord are improving.

The project relies on a strong stakeholder involvement and cooperation with the local fisheries association and local users of the fjord. Field work, including mussel production and deployment of the mussel reefs has been carried out by volunteers from the local Fisheries Association supervised by the Nordshell consultant and DTU Aqua staff.

The project is coordinated by DTU Aqua.


  • Research area: Marine Habitats
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ID: 2289031