Abstract
A desk study on potential effects of subsea cables on species in the North Sea (Snoek et al. 2016), showed field measurements of EMFs are scarce. This report presents the results of EMF field measurements carried out in 2019 as well as the results from the video observations of mobile megafauna simultaneously recorded and an update of international scientific literature regarding EMFs and effects on marine life (in the North sea). The developed methodology consisting of a measurement sledge equipped with real-time EMF measurements in combination with video recordings, has proven to be a valuable method to accurately determine the cable, measure EMF values and make recordings of the marine life above and in the vicinity of the cables. There are still operational limitations with respect to wave height that needs to be improved in order to be able to measure under maximum power production conditions as well. Measured EMF values are relatively low, since measurements are conducted during low wind speeds only due to operational limits. Still, EMF values are in the same range in comparison to measurements at OWF export cables in Belgium. The collected dataset was - due to the mentioned operational limits - too limited to be used for model validation. Based on a single observation, for at least two species groups a difference in density directly above the cable compared to areas further away was observed. Considering that this is only a single observation and no repeated quantitatively research and analysis could be conducted, no firm conclusions could be drawn from the results of this field study. This study shows demonstrates the feasibility of conducting EMF measurements in combination with camera observations above offshore OWF export cables and forms a solid basis for future research aiming at a more quantitative assessment of both EMF values and impact on marine life.