Effects of an Electric Field on White Sharks: In Situ Testing of an Electric Deterrent

Abstract

Elasmobranchs can detect minute electromagnetic fields, <1 nVcm–1, using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7™ electric deterrent on (1) the behaviour of 18 white sharks (Carcharodon carcharias) near a static bait, and (2) the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks.

Operant avoidance learning in crayfish, Orconectes rusticus: Computational ethology and the development of an automated learning paradigm

“…Punishment via electric-shock is perceived as aversive in a wide range of taxa (Glotzbach et al, 2012;Iwata & LeDoux, 1988;Vergoz et al, 2007) and has seen many applications in behavior modification. Uses range widely from keeping sharks away from swimmers (Huveneers et al, 2013), restricting livestock to particular spatial confines (Fay et al, 1989), and controlling barking in dogs (JuarbeDiaz & Houpt, 1996). Impacts on human psychological phenomena have included effects on learned helplessness (Overmier & Seligman, 1967), obedience (Milgram, 1963), and the control of fetishes (Bond & Evans, 1967), self-injurious behavior in autistic children a b Fig.…”

Effects and effectiveness of lethal shark hazard management: The Shark Meshing (Bather Protection) Program, NSW, Australia

“…e Gibbs and Warren (, ); McPhee (); Meeuwig and Ferreira (); Pepin‐Neff and Wynter (); Simpfendorfer et al (). f Department of Primary Industries (n.d.‐b); Hazin and Afonso (); Huveneers et al (); McPhee and Blount (); O'Connell, Stroud, et al ()). g Department of Industry and Investment (); Department of Primary Industries (, , , , , , , ): Krogh and Reid ().…”

“…Gibbs & Warren, , ; McPhee, ; Meeuwig & Ferreira, ; Pepin‐Neff & Wynter, ; Simpfendorfer, Heupel, White, & Dulvy, ). Concurrently, related concerns are driving innovation and investment in non‐lethal techniques, including personal electrical and visual deterrents, underwater barriers and deterrents using light, sound, air and magnet technologies, and underwater and aerial surveillance (Department of Primary Industries n.d.‐b; Hazin & Afonso, ; Huveneers et al, ; McPhee & Blount, ; O'Connell, Stroud, & He, ; see Figure ). Scientific and technological development and changing attitudes exert new pressures, which will inevitably continue to change the Program's form.…”

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Moving beyond lethal programs for shark hazard mitigation

“…Healthy shark populations increasingly generate significant tourism dollars and associated economic benefits for local communities, including species usually considered ‘dangerous’ (Gallagher & Hammerschlag, ). Finally, improvements in our understanding of shark biology derived from, for instance, telemetry and neuroscience can underpin nonlethal mitigation strategies such as warning systems predicated on movements and deterrents (Hammerschlag, Gallagher & Lazarre, ; Huveneers et al ., ).…”