Suitability for the development of flat oyster populations in new offshore wind farm zones and two search areas for restoration projects in the Dutch section of the North Sea

van Duren, Luca; Kamermans, P.; Kleissen, Frank


The Ministry of Agriculture, Nature and Food Quality has requested Deltares and Wageningen Marine Research (WMR) to execute an assessment of areas on suitability for restoration projects of the European flat oyster (Ostrea edulis). The study concerns eight designated wind farm zones for wind farm development before 2030 for their suitability for nature-inclusive design projects and two areas on the Frisian Front in future exclusion zones for bottom trawling, for large-scale restoration projects for oyster reefs. The assessment was made on available information of habitat suitability for oyster reefs and dispersal models for larvae.
Of the wind farm zones, only one (Wind Farm Zone 5 East) appears to be suitable for oyster restoration purposes. This area has abiotic habitat conditions conducive to the presence of oyster reefs and good larval retention. It is located within the historic distribution area of the species. The other wind farm zones are likely unsuitable for restoration projects, in most areas the presence of mobile bed forms is inhibitive for the formation of sustainable oyster beds. Two of the wind areas may have potential for the cultivation of oyster larvae for the purpose of restoration (Wind Farm Zone 1 North and Wind Farm Zone 2 North). Larvae produced in these areas have a reasonable probability of reaching suitable habitat and serve as a source for oyster larvae. The other wind farm zones may be biologically suitable for off-bottom cultivation, but larvae are unlikely to reach suitable habitat in one dispersal event.
The two potential restoration areas in the Frisian Front area both appear to be suitable. Both have a high suitability in terms of habitat for oyster reefs, high larval retention and from both locations larvae can also reach other suitable habitat that is protected from bottom trawling (either area that is in the future exclusion zone for fishing or future wind farm areas). Based on the information available there is very little difference between these sites in terms of suitability