Charged Encounters: effects of electromagnetic fields on sharks and rays

Offshore wind farms are expanding rapidly in the North Sea, bringing more subsea power cables into the habitat of sharks and rays. These cables generate electromagnetic fields, which may be detected by elasmobranchs because they naturally use electric and magnetic cues to find prey, navigate and interact with each other. This thesis investigated whether these fields affect small-spotted catsharks and thornback rays at different life stages, from embryos to juveniles and adults. The results show no strong avoidance, attraction or stress responses, but do reveal subtle changes in embryo movement, growth and swimming behaviour. Responses differed between species, life stages and sex. This means that electromagnetic fields are unlikely to cause dramatic short-term effects, but subtle long-term impacts cannot yet be ruled out. The thesis therefore advocates a balanced approach: optimise grid design, whilst improving monitoring and focus research on vulnerable species and life stages. This will provide input to weight the positive and negative aspects of offshore wind.