Prospective modelling of operational offshore windfarms on the distribution of marine megafauna in the southern North Sea

Intense development of Offshore Wind Farms (OFWs) has occurred in the North Sea with several more farms planned for the near future. These OFWs pose a threat to marine megafauna stressing the need to mitigate the impact of human activities. To help mitigating impacts, the Before After Gradient (BAG) design was proposed. We thus explored the use of the BAG method on megafauna sightings recorded at different distances from wind farms in the southern North Sea. We predicted intra-annual variability in species distribution, then correlated species distribution with the presence of operational OFWs and investigated the potential impact the operation of prospective OFWs may have on species distribution. Three patterns of intra-annual variability were predicted: species present most abundantly in spring, in winter or all year-round. We recommend that future OFW constructions be planned in summer and early fall to minimise impact on cetaceans and that offshore areas off northern France and Belgium be avoided to minimise impact on seabirds. Our prospective analysis predicted an increased or a decreased density with the operation of prospective OFWs. Prospective approaches, using e.g. a BAG design, are paramount to inform species conservation as they can forecast the likely responses of megafauna to anthropogenic disturbances. ### Competing Interest Statement The authors have declared no competing interest.