From subsea power cable to small-spotted catshark Scyliorhinus canicula: Behavioural effects of electromagnetic fields in tank experiments

Subsea power cables are expanding in number and capacity due to increasing demand to transport offshore generated energy. Energy transported through a cable creates an electromagnetic field (EMF). Elasmobranchs are dependent on their perception of the earth's magnetic field and biologically induced electric fields, for orientation, navigation, locating conspecifics and detecting prey. EMF levels from subsea power cables will add to natural signals potentially disrupting elasmobranch perception, but the effects are not fully understood. Reported behavioural responses include attraction, disturbance, and indifference, varying with exposure type, level and experimental set-up. In this study, the effects of EMF on swimming behaviour of 14 individual small-spotted catshark Scyliorhinus canicula were studied. All sharks were exposed to field-relevant EMF gradients cables in three trials: 15.0 μT AC, 19.6 μT DC, and a control treatment. Sharks showed no startle response to EMF onset, did not alter movement towards or away from the cable, and crossed it as frequently as in control trials. Hidden Markov Models showed that behavioural states were best explained by EMF treatment, trial order and sex. Sharks showed 25 % less time transiting during DC trials when compared to AC and control trials. These findings indicate reason for further refined studies to better determine behavioural effects from direct current subsea power cables with S. canicula, for example using tagging studies. In addition, exploring effects on other species will help obtain a broader understanding of the potential impacts of EMF on benthic elasmobranchs.