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. 2020 Feb 27;10(1):3563.
doi: 10.1038/s41598-020-60062-x.

Response of blacktip reef sharks Carcharhinus melanopterus to shark bite mitigation products

Madeline Thiele  1 , Johann Mourier  2   3   4 , Yannis Papastamatiou  5 , Laurent Ballesta  6 , Eric Chateauminois  7 , Charlie Huveneers  8
Affiliations

Response of blacktip reef sharks Carcharhinus melanopterus to shark bite mitigation products

Madeline Thiele et al. Sci Rep. .

Abstract

Globally, the frequency of shark bites is rising, resulting in an increasing demand for shark deterrents and measures to lessen the impact of shark bites on humans. Most existing shark protection measures are designed to reduce the probability of a bite, but fabrics that minimise injuries when a shark bite occurs can also be used as mitigation devices. Here, we assessed the ability of the Ocean Guardian Scuba7 and Kevlar material to reduce the likelihood of blacktip reef sharks, Carcharhinus melanopterus, from feeding, and to minimise injuries from shark bites. Sharks were enticed to consume a small piece of local reef fish (bait) placed between the two Scuba7 electrodes with the deterrents randomly being turned on or kept off. In the second experiment, the bait was attached to a small pouch made of either standard neoprene or neoprene with a protective layer of Kevlar around it. The Scuba7 reduced the proportion of baits being taken by 67%, (from 100% during control trials to 33%). Sharks also took more time to take the bait when the device was active (165 ± 20.40 s vs. 38.9 ± 3.35 s), approached at a greater distance (80.98 ± 1.72 cm vs. 38.88 ± 3.20 cm) and made a greater number of approaches per trial (19.38 ± 2.29 vs. 3.62 ± 0.53) than when the Scuba7 was inactive. The sizes of punctures from shark bites were significantly smaller on neoprene with Kevlar compared to standard neoprene (3.64 ± 0.26 mm vs. 5.88 ± 0.29 mm). The number of punctures was also fewer when Kevlar was used (14.92 ± 3.16 vs. 74.1 ± 12.44). Overall, the Ocean Guardian Scuba7 and Kevlar reduced the impact of blacktip reef shark bites. These findings may help consumers make informed decisions when purchasing shark deterring and protective products.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Diagram showing the experimental set-up and the two dominant current directions during the trials. Image drawn by the authors using SketchUp (www.sketchup.com).
Figure 2
Figure 2
Effects of the Scuba7 on blacktip reef sharks (Carcharhinus melanopterus) on (a) time taken to take the bait; (b) percentage of baits taken; (c) number of approaches per trial; (d) distance to the electrode; (e) body reactions (white = approaches with no reaction, light grey = reaction during outside approaches, darker grey = reaction during in-between approaches); and (f) logistic regression of the likelihood of a reaction occurring as distance from electrode increases for trials when the Scuba7 was off (top) and on (bottom). Mean values are indicated by the crosses; median by the horizontal bar; the length of the box is the inter-quartile range; whiskers represent quartiles; and circles are extreme values.
Figure 3
Figure 3
Damage of blacktip reef shark (Carcharhinus melanopterus) bites on standard and Kevlar-neoprene, based on (a) size of the holes; (b) number of holes per trial; and (c) percentage of holes that went through the fabric.
Figure 4
Figure 4
Theorical electric field strength overlayed for electrodes in Mid-water (full lines), close to the surface (dashed lines), close to a non-conductive seabed (dashed-dot lines), and close to a conductive seabed (dotted lines) in (a) horizontal plane (Z = -55 cm) and (b) vertical plane Y = 0 cm). Coloured lines represent the magnitude of the electric field (red: 1 Vm-1; cyan: 10 Vm-1); white lines represent the vector field lines for (b) and a projected vector field line on the horizontal plane for (a).
Figure 5
Figure 5
Field strength that sharks were exposed to when crossing through the dipole axis along (a) three different approach directions (parallel = green; perpendicular = red; diagonal = blue) and for (b) four model situations (Mid-water = full line; Surface = dashed line; non-conductive seabed = dashed-dot line; conductive seabed = dotted line). Note that dashed lines are difficult to see because they overlay on top of the full lines.
See this image and copyright information in PMC

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