Female crabs are more sensitive to environmentally relevant electromagnetic fields from submarine power cables

The expansion of offshore wind and marine renewable energy devices (MREDs) is increasing anthropogenic electromagnetic fields (EMFs) from submarine power cables (SPCs). SPC-generated EMFs can exceed 2700 μT, well above the geomagnetic field, and may affect benthic animal behavior. In decapod crustaceans, sex-specific habitat uses and seasonal migrations are well-documented, yet their role in EMF sensitivity remains untested. We exposed juvenile shore crabs (Carcinus maenas) (n = 120; 1:1 sex ratio) to EMFs of 500, 1000, and 3200 μT using a Helmholtz coil system and tracked behavior over 10 min trials. Females exhibited strong attraction across EMF levels, spending up to 131% more time in the EMF-exposed zone and significantly less time in the low-field zone. They also drove differences in distance moved, whereas males showed no consistent spatial preference and indifferent activity at the highest field strength. These sex-specific responses suggest SPC EMFs could disrupt female-driven reproductive behaviors like seasonal migrations and larval release. Attraction may cause disorientation, aggregation, or delays in migration, potentially altering sex ratios and reducing larval export. This study provides the first evidence of sex-specific EMF responses in crustaceans and highlights the importance of incorporating sex as a key variable in ecological risk assessments of offshore infrastructure.