Shark deterrents: do they really work?
ONE TYPE OF electronic shark deterrent, that used a 2m-long cord, has been identified as “promising” by independent researchers at the University of Western Australia (UWA).
During trials, the Shark Shield – a commercial product that claims to deter sharks by emitting electrical impulses from a 2m long trailing line – was nearly 90 per cent effective at repelling or deterring white sharks (known popularly as great white sharks, Carcharodon carcharias) from a baited rig.
The UWA researchers also concluded that an alternative electric ankle deterrent and loud underwater sounds, including orca noises, appeared to have negligible effects.
On average, one person is killed by a shark each year in Australia.
These preliminary findings were made by a research team funded under the WA state government’s shark deterrant program. The team, which included UWA Oceans Institute Director Professor Shaun Collin, Associate Professor Nathan Hart and Dr Ryan Kempster have been trialling the devices both in the lab and off the coast of South Africa.
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Trailing shark deterrent the most effective
Ryan stressed that more research is needed to be “statistically confident in the species-specific effects” when he spoke to Australian Geographic.
Because the Shark Shield has a long trailing antenna, the electrodes are spread much further apart than is possible on just the anklet alone. This seems to make all the difference, because there was “no significant reduction in the number of (shark) interactions” with the anklet, says Ryan.
The researchers also made clear that despite a prevailing myth, their research suggests that electrical impulses from these devices will not actively attract sharks.
While some of the other deterrents seemed promising, when tested in the field, they didn’t stack up. Nathan said that while “strobe lights were quite effective in the lab”, but out in the ocean “white sharks certainly weren’t scared”.
The researchers concluded that strobe lights were effective only for strongly nocturnal or bottom dwelling shark species.
A curtain of bubbles was another deterrent tested, with mixed results. According to Nathan “a burst of bubbles let off very quickly” when a shark approached was “quite effective at scaring off white sharks.” However, the effect was short-lived and sharks quickly became used to the bubbles and often returned.
Nathan said the bubble strategy could be an option for divers in an emergency, if they had time to do so.
The researchers were quick to note that this is early days for the research and that full details on the effectiveness of these devices will be provided in peer-reviewed publications later this year. Shaun added that he hoped that this research would “ultimately lead to the development of new shark deterrent technologies in the future”.
Shark deterrents: key early findings
- A device with a trailing antenna that emits three dimensional electronic fields, such as the Shark Shield, has been shown to deter sharks from a baited rig roughly 90 per cent of the time.
- A curtain of bubbles, depending upon its presentation, may repel some species of sharks. Sharks generally acclimatise quickly, however, and cross the bubble barrier without fear.
- Ankle devices that emit electrical currents but have no trailing antenna were not shown to be effective in deterring sharks.
- Despite theories that loud noises or the noises of killer whales may deter or frighten sharks, they made no impact in the lab and had limited effectiveness in the field. Scientists concluded that sharks may be frightened by the presence of killer whales, not their sounds.
- Strobe lights did not deter white sharks, but may have some deterrent effects on strongly nocturnal sharks or bottom dwelling species.
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