Not all electric shark deterrents are made equal: Effects of a commercial electric anklet deterrent on white shark behaviour

• Published in: PloS one Vol. 14; no. 3; p. e0212851
• Main Authors: Egeberg, Channing A, Kempster, Ryan M, Hart, Nathan S, Ryan, Laura, Chapuis, Lucille, Kerr, Caroline C, Schmidt, Carl, Gennari, Enrico, Yopak, Kara E, Collin, Shaun P
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 11.03.2019; Public Library of Science (PLoS)
• Subjects: Analysis; Animal behavior; Animals; Baits; Behavior; Behavior Observation Techniques - methods; Biology and Life Sciences; Bites and Stings - prevention & control; Biting; Carcharodon carcharias; Deterrents; Earth Sciences; Electric fields; Electrical shielding; Engineering and Technology; Female; Fishes; Human behavior; Humans; Indian Ocean; Motor Activity - physiology; Oceanography; Oceans; Physical Sciences; Physiology; Predatory Behavior; Reduction; Remote Sensing Technology - methods; Risk reduction; Sharks; Sharks - physiology; Social Sciences; South Africa; Video Recording - methods; Wearable Electronic Devices; White shark; Indian Ocean; South Africa; Australia; United States > US; Western Australia Australia; New South Wales Australia; Bahamas
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0212851

Personal shark deterrents offer the potential of a non-lethal solution to protect individuals from negative interactions with sharks, but the claims of effectiveness of most deterrents are based on theory rather than robust testing of the devices themselves. Therefore, there is a clear need for thorough testing of commercially available shark deterrents to provide the public with information on their effectiveness. Using a modified stereo-camera system, we quantified behavioural interactions between Carcharodon carcharias (white sharks) and a baited target in the presence of a commercially available electric anklet shark deterrent, the Electronic Shark Defense System (ESDS). The stereo-camera system enabled accurate assessment of the behavioural responses of C. carcharias when approaching an ESDS. We found that the ESDS had limited meaningful effect on the behaviour of C. carcharias, with no significant reduction in the proportion of sharks interacting with the bait in the presence of the active device. At close proximity (< 15.5 cm), the active ESDS did show a significant reduction in the number of sharks biting the bait, but this was countered by an increase in other, less aggressive, interactions. The ESDS discharged at a frequency of 7.8 Hz every 5.1 s for 2.5 s, followed by an inactive interval of 2.6 s. As a result, many sharks may have encountered the device in its inactive state, resulting in a reduced behavioural response. Consequently, decreasing the inactive interval between pulses may improve the overall effectiveness of the device, but this would not improve the effective deterrent range of the device, which is primarily a factor of the voltage gradient rather than the stimulus frequency. In conclusion, given the very short effective range of the ESDS and its unreliable deterrent effect, combined with the fact that shark-bite incidents are very rare, it is unlikely that the current device would significantly reduce the risk of a negative interaction with C. carcharias.