Effectiveness of five personal shark-bite deterrents for surfers

Charlie Huveneers; Sasha Whitmarsh; Madeline Thiele; Lauren Meyer; Andrew Fox; Corey J A Bradshaw

doi:10.7717/peerj.5554

Effectiveness of five personal shark-bite deterrents for surfers

PeerJ. 2018 Aug 31:6:e5554. doi: 10.7717/peerj.5554. eCollection 2018.

Authors

Charlie Huveneers¹, Sasha Whitmarsh¹, Madeline Thiele¹, Lauren Meyer¹, Andrew Fox², Corey J A Bradshaw³

Affiliations

¹ Southern Shark Ecology Group, College of Science and Engineering, Flinders University, Adelaide, Australia.
² Fox Shark Research Foundation, Adelaide, South Australia, Australia.
³ Global Ecology, College of Science and Engineering, Flinders University, Adelaide, Australia.

Abstract

The number of shark-human interactions and shark bites per capita has been increasing since the 1980s, leading to a rise in measures developed to mitigate the risk of shark bites. Yet many of the products commercially available for personal protection have not been scientifically tested, potentially providing an exaggerated sense of security to the people using them. We tested five personal shark deterrents developed for surfers (Shark Shield Pty Ltd [Ocean Guardian] Freedom+ Surf, Rpela, SharkBanz bracelet, SharkBanz surf leash, and Chillax Wax) by comparing the percentage of baits taken, distance to the bait, number of passes, and whether a shark reaction could be observed. We did a total of 297 successful trials at the Neptune Islands Group Marine Park in South Australia, during which 44 different white sharks (Carcharodon carcharias) interacted with the bait, making a total of 1413 passes. The effectiveness of the deterrents was variable, with the Freedom+ Surf affecting shark behaviour the most and reducing the percentage of bait taken from 96% (relative to the control board) to 40%. The mean distance of sharks to the board increased from 1.6 ± 0.1 m (control board) to 2.6 ± 0.1 m when the Freedom Surf+ was active. The other deterrents had limited or no measureable effect on white shark behavour. Based on our power analyses, the smallest effect size that could be reliably detected was ∼15%, which for the first time provides information about the effect size that a deterrent study like ours can reliably detect. Our study shows that deterrents based on similar principles-overwhelming a shark's electroreceptors (the ampullae of Lorenzini) with electrical pulses-differ in their efficacy, reinforcing the need to test each product independently. Our results will allow private and government agencies and the public to make informed decisions about the use and suitability of these five products.

Keywords: Human protection; Human-wildlife conflicts; Mitigation measures; Shark attack; Shark repellents.

Grants and funding

This project was funded by the New South Wales Department of Primary Industries Shark Management Strategy (SMS) Competitive Annual Grants Program, Government of South Australia, Ocean Guardian Pty Ltd, and the Neiser Foundation. We openly and transparently declare that Ocean Guardian contributed financially to the study, but that Ocean Guardian was not involved in the study design or implementation, nor did they have access to the data post-collection. Nor did Ocean Guardian provide input into data analysis, interpretation, writing of the manuscript, or the conclusions drawn. The study design followed a protocol developed for a previous study (Huveneers et al. 2013b), which was not funded by Ocean Guardian. In summary, Ocean Guardian had no opportunity to influence any aspect of the study or its conclusions, apart from providing some financial support to realise the field project (e.g., boat hire, equipment purchase, etc.) in the same manner as the other funding agencies. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.