Effects of anthropogenic magnetic fields on the behavior of a major predator of the intertidal and subtidal zones, the velvet crab Necora puber

With the progress of the offshore renewable energy sector and electrical interconnection projects, a substantial rise in the number of submarine power cables is expected soon. Such cables emit either alternating or direct current magnetic fields whose impact on marine invertebrates is currently unknown and hardly studied. In this context, this study aimed to assess potential short-term exposure (30 min) effects of both alternating and direct magnetic fields of increasing intensity (72–304 μT) on the behavior of the high-ecological value velvet crab (Necora puber). Three experiments were designed to evaluate whether the strongest magnetic field intensities induce crabs’ attraction or repulsion responses, and whether foraging and sheltering behaviors may be modified. We extracted from video analyses several variables as the time budgets crabs spent immobile, moving, feeding, or sheltering as well as total and maximal distance reached in the magnetic field (MF) gradient. The crabs exposed to artificial MF did not exhibit significant behavioral changes compared with those exposed to the “natural” MF. Overall, our results suggest that, at such intensities, artificial magnetic fields do not significantly alter behaviors of N. puber. Nevertheless, future studies should be conducted to examine the effects of longer exposure periods and to detect potential habituation or resilience processes.