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Testing the performance of long-range electric deterrents for reducing the risk of shark bite

shark


R code, data files, and references accompanying paper in review:

Riley, M, CJA Bradshaw, C Huveneers. 2022. Long-range electric deterrents not as effective as personal deterrents for reducing risk of shark bite. ICES Journal of Marine Science 79: 2656-2666

Abstract

While personal electric deterrents can reduce the risk of shark bite, evidence for the efficacy of other products is limited. We assessed two versions of a novel electric deterrent — 80 volts (V) and 150 V — designed to protect a large area (8 m deep × 6 m wide) or to be linked together for greater spatial coverage. We did 116 experimental trials on 43 white sharks (Carcharodon carcharias) to assess: (a) percentage of baits taken, (b) distance between bait and shark, (c) number of passes, and (d) whether sharks reacted to the deterrent. The proportion of baits taken reduced by 24% (80 V) and 48% (150 V), although high variance of the effect coefficient precluded statistical differentiation. Only the 150-V deterrent increased the distance between bait and shark (control: 1.59 ± 0.28 m versus active deterrent: 3.33 ± 0.33 m), but both versions increased the likelihood of a reaction (average reaction distance: 1.88 ± 0.14 m). Results were similar whether we measured distance using stereo-cameras or estimated them in situ, suggesting that stereo-cameras might not be necessary to quantify distances between sharks and baits. Our findings provide more evidence that electric deterrents can reduce the risk of shark bite, but the restricted efficacy limits the suitability of this device.

Experimental set-up during deterrent-test trials, showing (a) the entire experimental set-up and (b) the stereo-camera

Required R libraries

  • lme4
  • boot
  • Hmisc
  • ggplot2
  • plyr
  • ggpubr
  • dplyr
  • tidyr
  • tidyverse
  • hrbrthemes
  • viridis

Also accompanying the code are two source files with additional functions necessary to reproduce the analyses (r.squared.R & new_lmer_AIC_tables3.R)

References

We also provide some PDF copies of relevant references cited in the paper (in the refs folder):

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