A study conducted by Wageningen University & Research has revealed that artificial reefs installed within offshore wind farms are highly attractive to Atlantic cod, with the fish spending significant time around them. Published in the scientific journal Royal Society Open Science, the study offers key insights into whether marine species can benefit from the reintroduction of hard substrates, such as artificial reefs, in the North Sea’s wind farms.
In 2020, four artificial reefs were installed within the Borssele 1&2 offshore wind farm. These structures, made up of 45 concrete tubes of varying sizes, were part of a long-term experiment. More than 60 cod were captured and fitted with acoustic transmitters near the reefs. In addition, 16 receivers were positioned around the reefs to track the movement of the tagged fish. The data collected provided detailed insights into the behavior and movement patterns of the cod.
The study results indicated that most of the tagged cod remained close to the reefs for extended periods. The fish also spent significant time hiding inside and around the concrete tubes, suggesting that these structures play a crucial role as both feeding grounds and shelters for the species.
Artificial Reefs Outperform Conventional Erosion Protection
The research presents valuable insights into eco-friendly construction within offshore wind farms, specifically regarding habitat creation for North Sea species. The artificial reefs proved more attractive to cod than the conventional stone-based erosion protection surrounding the wind turbines. The larger openings of the concrete tubes offer better shelter for the fish. Interestingly, two of the artificial reefs were installed on a layer of stones, while the other two were placed directly on the sandy seabed, with both designs attracting cod equally.
Reefs: A Path to Marine Biodiversity Restoration?
Offshore wind farms can negatively affect marine ecosystems during construction and operation, due to factors like underwater noise and habitat degradation. However, Benoît Bergès, lead researcher and marine biologist at Wageningen Marine Research, sees potential for positive contributions through habitat creation. “I’m looking forward to further exploring the availability of food and energy consumption of fish around artificial reefs and determining if these structures actually enhance fish reproduction and contribute to larger population growth,” Bergès noted.
After the completion of Borssele 1&2 in 2020, Ørsted and Wageningen University & Research launched a monitoring program in 2021 and 2022 to observe how Atlantic cod interacted with the artificial reefs. The study focused on assessing the use of these reef structures by cod and how they impacted the species’ behavior in the wind farm environment.
