Following acoustic detections of bats at the Dieppe Le Tréport offshore wind farm site during the initial impact assessment phase, the Eolien en Mer SIG decided to conduct a study on bat transits at sea.

This study, carried out by the CESCO laboratory of the National Museum of Natural History, aims to determine the species present around the Dieppe Le Tréport wind farm, compare passages at sea, on the coast and further inland, determine whether these passages correspond to migratory movements and identify the meteorological factors that influence these activities. In addition, the data collected is being incorporated into the MIGRATLANE project, which aims to understand the use of the Atlantic-Channel-North Sea arc by birds and bats.

This first report details the analysis of data collected in 2023. It shows that at least nine species were detected at sea, only in autumn and later at night than on land. The differences in observations between land-based sites and the sea buoy may be linked to differences in acquisition parameters, abundance or species behaviour.

These preliminary results will be supplemented by several years of recordings, which will provide a better understanding of the influence of weather conditions and interannual variations in bat transits at sea.