Evaluating the effects of a SharkSafe Barrier™ shoreline deployment on bull shark (Carcharhinus leucas) behaviour

Abstract

1. Beach nets and drumlines are lethal devices that are used to minimize the interaction between potentially dangerous sharks and beachgoers. Mortality to these large shark species as a result of these lethal measures has led to the development of non-invasive technologies that may minimize the risks of rare encounters with beachgoers while simultaneously protecting vulnerable sharks and other marine species.2. One such technology is the SharkSafe Barrier™, which uses visual and magnetic stimuli to non-invasively deter sharks from a designated area. Previous experiments using this technology were performed on a small scale (e.g. 13 m  13 m), with an attempt made to extrapolate the results to a larger scale application without actual large-scale deployments and experimentation.3. The present study examined whether a large-scale SharkSafe Barrier™ shoreline deployment could successfully exclude the bull shark (Carcharhinus leucas) from acoustic and olfactory cues and evaluated whether the technology could serve as a less invasive replacement to current culling practices.4. Generalized linear mixed-model analyses based on 59 trials illustrate that C. leucas swimming behaviour (i.e. avoidances, entrances, and pass arounds) significantly differed between the control (i.e. unmanipulated area) and the experimental (i.e. SharkSafe Barrier™) regions. Unlike previous small-scale experiments, 10 of 16 sharks repeatedly penetrated the barrier and swam in an accelerated manner once within the experimental barrier region.5. The present findings raise concerns that the size of the previous experimental areas may have been insufficient to provide a realistic representation of barrier efficacy for large-scale deployments. With continued shark-culling measures in various locations, a non-invasive and eco-friendly alternative is needed, but substantial modifications to the current Sharksafe barrier design or an entirely new eco-friendly approach are needed as the barrier in its present state does not reliably deter large and potentially dangerous sharks from a large-scale area.

Evaluating the potential white shark (Carcharodon carcharias) swim pattern manipulation capabilities of the novel and noninvasive Shark Exclusion Barrier

“…City of Cape Town, 2013; Engelbrecht et al, 2017); however, other technologies have exhibited shortcomings in shark exclusion effectiveness (e.g. SharkSafe Barrier; O'Connell et al, 2021) and/or the ability to withstand high‐energy environments. Therefore, there remains a need to develop an eco‐friendly alternative to lethal shark culling measures that can both provide highly reliable shark exclusion capabilities and maintain its structural integrity in a high‐energy environment.…”

“…the visual stimulus) that forms a semirigid structure, (2) 3 V solar panels attached directly to a DC 3 V 25 N electromagnet and strategically spaced Barium Ferrite (BaFe 12 O 19 ) permanent magnets that create a continuous magnetic field throughout the entirety of the barrier (i.e. the electrosensory stimulus) and (3) a telescoping piping component at the surface of the barrier to facilitate a continuous seafloor to sea surface visual barrier regardless of variation in tidal height and wave activity (O'Connell et al, 2021; see Figure 1). The visual component of the barrier (i.e.…”

Personal electric deterrents can reduce shark bites from the three species responsible for the most fatal interactions

“…For example, enclosures are only suitable for bathers in areas protected from large swells and land or aerial shark spotting is not applicable to divers 16 . Exclusion barriers that incorporate magnets 19 or electromagnets 20 have been developed for exposed conditions, but they do not stop all sharks and are expensive to deploy and maintain across large areas. There remains a need for measures protecting surfers and divers, which represents a large proportion of shark-bite victims 9 .…”