The diet of demersal and semi-pelagic fish in the Thorntonbank wind farm: tracing changes using stomach analyses data

This chapter focuses on the diet of six demersal and semi-pelagic fish species (dab, solenette, dragonet, lesser weever, whiting and horse mackerel) in the Thorntonbank wind farm and its surrounding areas. Stomach analyses were conducted to unravel changes in feeding patterns and to discriminate between effects of the presence of the turbines and effects as a result of fisheries displacement at the border of the wind farm concession area. Differences were observed between impact, fringe and reference stations. The fullness index indicated that fish had a fuller stomach close to the wind turbines and at the borders of the concession area. This might be an indication of a higher
food availability around the wind turbines. The stomach content of dab revealed more amphipods and especially hard substratum species (e.g. Phtisica marina) in the impact area compared to the reference area. However, the most abundant hard substratum species present on the turbines (i.e. the amphipod
Jassa herdmani and the crab Pisidia longicornis) were not found in any of the dab stomachs. This can probably be linked to the sampling distance (500-1500m) or to the prey preferences of dab. In general, differences in feeding patterns between sampling stations were observed. Whether these differences originated from the wind turbine presence or from changes in fisheries activities can
only be unequivocally confirmed by replication within and between the wind farm(s) and by an optimisation of the sampling strategy.