Are Sharks and Rays Using Offshore Wind Farms as Habitats?

In new research, scientists from the Wageningen University & Research have confirmed regular activity by sharks and rays at offshore wind farms around the Netherlands. The team was able to confirm the presence of these elasmobranchs through traces of environmental DNA, or eDNA, in the waters around Dutch wind farms.

The researchers collected 436 seawater samples to analyze for DNA traces, a method that the team noted was affordable and non-invasive, making it more humane for the marine life. It served as an alternative to actually capturing any sharks or rays present in the study areas.

“It’s like finding a fingerprint in the water,” Annemiek Hermans, Ph.D. candidate at Wageningen University & Research, said in a statement. “Even if you don’t see the shark, the DNA tells you it’s been there.”

A researcher takes laboratory samples to analyze for DNA traces. Wageningen University & Research

The results, part of the university’s larger ElasmoPower project, revealed the presence of five shark and ray species at four offshore wind farms, including Borssele, Hollandse Kust Zuid, Luchterduinen and Gemini. Thornback rays (Raja clavata) were the most common and were present year-round at three of the offshore wind farms. The scientists published the results in the journal Ocean & Coastal Management.

The researchers were able to learn more about the migration of basking sharks (Cetorhinus maximus) through detecting their DNA around the Hollandse Kust Zuid wind farm during the winter. As Earth.com reported, the basking sharks’ winter migratory path in Dutch waters was previously unknown.

The Hollandse Kust Zuid wind farm. Esgian / Silco Saaman / s2foto

Other notable findings were the starry smooth-hound (Mustelus asterias) and the blonde ray (Raja brachyura). Both species were found at multiple offshore wind farm sites through various seasons.

“We’re trying to understand whether these animals are actually using the wind farms as habitat, or whether they’re being displaced by them,” Hermans explained.

The scientists noted that the elasmobranchs could be drawn toward the offshore wind farms because trawling is not allowed in these areas and fishing and shipping near wind farms comes with restrictions, which could potentially create safer areas that may benefit and attract marine life. The lack of seabed disturbance further allows smaller fish and other marine life to recover, creating a more abundant food source for sharks and rays, Earth.com reported. 

Ongoing research will be needed to determine whether the elasmobranchs are using the offshore wind farm sites as safe habitats and how they affect other marine life. In particular, the study authors warned that preventing seabed-disturbing activities in these areas will be vital for protecting marine life.

“We must tread carefully,” Hermans said. “If we start allowing bottom trawling in these areas, we risk losing the very protection these zones may offer.”