Responses of the southern stingray (Dasyatis americana) and the nurse shark (Ginglymostoma cirratum) to permanent magnets

Citation
O’Connell CP, Abel DC, Rice PH, et al (2010) Responses of the southern stingray (Dasyatis americana) and the nurse shark (Ginglymostoma cirratum) to permanent magnets. Marine and Freshwater Behaviour and Physiology 43:63–73. doi: 10.1080/10236241003672230
Abstract

The behavioral responses of free-swimming, wild southern stingrays (Dasyatis americana) and nurse sharks (Ginglymostoma cirratum) to permanent magnets were evaluated in the Florida Keys, USA. Animals were attracted to a baited magnetic treatment board consisting of two 15 cm × 10 cm × 5 cm grade C8 Barium-Ferrite (empirically, BaFe12O19) permanent magnets producing a flux of 950 gauss at their surface and a baited procedural control board containing two smooth nonmagnetized clay bricks. In the presence of permanent magnets, D. americana and G. cirratum demonstrated a significantly greater number of avoidance behaviors away from the magnet side of the apparatus, while both species fed a significantly greater number of times from the non-magnetized procedural control side. Thus, D. americana and G. cirratum showed sensitivity to a magnetic field and were successfully repelled from baited areas containing magnets. The results from the current study suggest that the use of grade C8 Barium-Ferrite permanent magnets as an avoidance mechanism (e.g., repellent) to reduce elasmobranch mortalities associated with fishing operations and beach nets merits further investigation.