MAGNIFISH · Framing the risks: Assessing the impact of MAGNetic fIelds from offshore wind farms on migratory FISH

Europe is at the forefront of the renewable energy transition, with the expansion of offshore wind farms, but the deployment of power subsea cables introduces a ubiquitous yet poorly understood anthropogenic stressor: magnetic fields (MFs). These MFs exceed Earth’s natural geomagnetic field and induce behavioural and physiological changes in marine species, suggesting a stress response. One of the knowledge gaps in this field is the neuroendocrine signaling system that controls behavioural and physiological stress responses in fish. Moreover, magnetosensitive fishes that rely on geomagnetic cues for migration are likely to be more vulnerable to anthropogenic MFs. The MAGNIFISH project focuses on the European eel that is a pertinent model species due to its critically endangered status, magnetosensitivity, and exposure to power grids during its inland and seaward migrations. Thus, eels provide a broadly applicable framework for assessing and mitigating MF impacts on other commercially important migratory fishes. I will establish dose-response reaction norms in two early life stages (glass eels and elvers) across an environmentally relevant gradient of MF intensities (50-380 µT). This will pinpoint response thresholds across biological scales—from neuroendocrine regulation to physiological and behavioural changes—and identify most vulnerable life stages to anthropogenic MFs. Subsequently, I will test if MF exposure alters the innate magnetic orientation behaviour in migratory fish, directly assessing impacts on migratory success. The resulting predictive risk assessment framework will determine MF intensities that compromise fish migratory success and fitness, and estimate the distance from cables at which migrating species would be affected. MAGNIFISH will generate new insights and knowledge into MF impact research, ultimately improving environmental risk assessments, guiding effective conservation strategies, and informing sustainable offshore energy development.