Behavioural responses in the sand tiger shark (Carcharias taurus) to permanent magnets and pulsed magnetic fields

ABSTRACT

Sharks are threatened by several human activities that impact their distribution and abundance. A great proportion of shark captures happen as incidental capture (bycatch) by fisheries and in beach nets. Recent studies have focused on reducing these captures by exploiting technologies that target the sharks’ electrosensory system, obtaining contrasting results. This study investigates the effect of a strong neodymium magnet and pulsed magnetic fields (PMFs) on captive sand tiger sharks (Carcharias taurus) through the analysis of their behavioural responses. Firstly, individuals were presented with the magnet in combination with different types of food. The magnet did not influence the sharks’ behaviours, while an effect of the food type emerged. Secondly, PMFs were generated through a pulsed electric current induced within a solenoid associated with a PVC structure. The PMFs affected some of the sharks’ behaviours, both near (<2 m) and at a distance (>2 m) from the source. The results suggest that strong magnets are inefficient in deterring sand tiger sharks, while PMFs could be a promising alternative. This study confirms how the efficacy of shark repellents may be affected by factors such as the type of electrosensory stimuli, the species involved, and the context in which the interaction takes place.

KEYWORDS:

• Bycatch mitigation
• elasmobranch
• electroreception
• magnetoreception
• shark mortality mitigation
• shark repellents

Acknowledgements

We would like to thank Prof. Carlo Cerrano (Department of Life and Environmental Sciences (DiSVA), Marche Polytechnic University, Ancona, Italy) for his intellectual and general support to the present work. We would also like to thank the staff of the Cattolica Aquarium for their practical help during the experimentation, and particularly Simone Fuzzi for having provided his time and expertise for the construction of the PVC structure. Finally, we would like to thank Giorgia Faraoni (School of Education, University of Leeds) for her review of the text in terms of grammatical and lexical accuracy.

Disclosure statement

No potential conflict of interest was reported by the author(s).