Abstract
Gemini offshore wind farm is located in the Dutch part of the North Sea, 85 km north of the coast of Groningen. The Gemini wind farm consists of 150 wind turbines, totalling 600 MW and two offshore high voltage stations. Start of construction was mid-2015. Gemini is fully operational since 2017. As part of Gemini’s environmental monitoring program, the presence of harbour porpoises in and around the wind farm was measured with a network of 15 passive acoustic monitoring devices (CPODs, see Figure 1), both prior to the construction of the wind farm and in the year in which the monopiles were driven (2015). In addition, aerial surveys were performed in a wide area around the wind farm. The results of these research efforts have been reported in two reports from Wageningen Marine Research (Geelhoed et al. 2015; Geelhoed et al. 2018). Post construction follow-up research within the framework of the environmental monitoring program of Gemini wind farm has focused on filling in a number of important knowledge gaps about the effects of disturbance caused by impulsive underwater sounds on the fitness of harbour porpoises. This knowledge at the individual level could then, in combination with the results of the field research carried out during the construction, be used to estimate with more certainty through model calculations what the (cumulative) effects of impulsive noise on the harbour porpoise population are. This report gives an overview of and summarizes the results of the work done with (part) funding form Gemini. The full reports of the research projects are included as appendices to this report.