ESR 26:243-256 (2015)  -  DOI: https://doi.org/10.3354/esr00629

Effects of barium-ferrite permanent magnets on great hammerhead shark Sphyrna mokarran behavior and implications for future conservation technologies

Craig P. O’Connell1,2,*, Saang-Yoon Hyun1, Samuel H. Gruber3, Pingguo He1

1School for Marine Science and Technology, University of Massachusetts Dartmouth, 706 South Rodney French Boulevard, New Bedford, MA 02744, USA
2O’Seas Conservation Foundation, Bronx, NY 10463, USA
3Bimini Biological Field Station, Bimini, Bahamas
*Corresponding author:

ABSTRACT: The great hammerhead shark Sphyrna mokarran is an endangered species that is exposed to several sources of anthropogenic mortality, including beach nets. Although not a major contributor to S. mokarran mortality, beach nets are utilized in several locations to minimize the potential harmful interaction between sharks and beachgoers. To address this mortality, permanent magnets have been employed to determine if these materials can deter sharks away from netted areas. The present study examined the effects of barium-ferrite (BaFe12O19) permanent magnets on S. mokarran behavior under several environmental and biological conditions. In the bait experiment, feeding frequency significantly decreased and avoidance frequency significantly increased with the magnet treatment, with exposure quantity yielding an increase in feeding frequency, although this effect was not statistically significant. For the barrier experiment, entrance frequency significantly decreased and avoidance and pass-around frequencies significantly increased with the magnet treatment, with heterospecific density also being a significant predictor of entrance frequency. The findings demonstrate how permanent magnets can modify S. mokarran behavior and how this behavior is modified based on situational context. Since several other sphyrnid species are caught in beach nets more frequently than S. mokarran (e.g. scalloped hammerheads S. lewini), the present results may serve as a model for these other sphyrnid species and illustrate the potential conservation implications of future magnetic deterrent barrier technologies.


KEY WORDS: Beach nets · Great hammerhead shark · Sphyrna mokarran · Permanent magnets · Elasmobranch mortality


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Cite this article as: O’Connell CP, Hyun SY, Gruber SH, He P (2015) Effects of barium-ferrite permanent magnets on great hammerhead shark Sphyrna mokarran behavior and implications for future conservation technologies. Endang Species Res 26:243-256. https://doi.org/10.3354/esr00629

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