The effects of an offshore wind farm on the diet of plaice using stomach content and stable isotope analysis

Silke De Buyser

The introduction of offshore wind farms (OWF’s) induces artificial reef effects all over the North Sea. While many studies have already demonstrated the attraction of hard substrate species towards OWF’s, only limited research is focused on the attraction of soft sediment species, such as flatfish. Building on recent observations of plaice (Pleuronectes platessa) being four times more abundant on the scour protection layer (SPL) around the turbines, we investigated whether the diet of plaice was significantly altered inside Belwind, an OWF in the Belgian part of the North Sea. This as a first step in approaching the attraction-production hypothesis for plaice concerning OWF’s. We combined a gastrointestinal content analysis with a stable isotope analysis and additionally calculated the stomach fullness and Fulton’s (condition) index. Results indicated better-fed conditions and a clear difference in plaice’s diet composition found on the SPL, showing greater food availability to play a key role in the attraction of plaice towards OWF’s. We were not able to conclude a long-term stay of plaice inside this wind farm, but some outcomes - like a higher Fulton’s index and a skewed sex ratio - do suggest the possibility of a refugium effect, implying a more prolonged stay.