Good news for ocean enthusiasts – if beachgoers wear personal electronic deterrents that can reduce the probability of a shark attack, scientists have calculated that hundreds of people could avoid injury, trauma or death in Australian waters over the next 50 years.
Corey Bradshaw, from Flinders University, South Australia, and his team set out to predict how many people could avoid a shark attack with electronic deterrents. These were scientifically shown to reduce the probability of an encounter by about 60%.
Internationally, Australia has the second highest number of recorded shark bites after the US, followed by South Africa, Brazil, Réunion and the Bahamas.
Bradshaw’s team investigated shark bites reported in the Australian Shark Attack File from 1900 to 2020 and found 985 incidents over the century, including 194 fatalities, from 20 different species including most commonly great white (Carcharodon carcharias), tiger (Galeocerdo cuvier), bull (Carcharhinus leucas) and whaler sharks.
Two-thirds of these were “unprovoked” encounters that didn’t involve direct interaction with sharks such as spearing, stabbing, handling or attracting them in some way.
“When someone gets bitten these days, it’s big news,” says Bradshaw, lead author of a paper published in the journal Royal Society Open Science.
“It also reinforces people’s fear of sharks, and the public pressure to intervene – often fatally. Sharks as a group aren’t doing well around the world, so they don’t need any more bad press.”
Of course, the loss of any life is tragic, he adds, and whole communities can lose tens to hundreds of millions of dollars in tourism revenue following attacks – adding to the need to intervene. Then there’s the post-traumatic stress experienced by victims.
The study’s findings are also good news for sharks, as the disproportionate hysteria and “emotional public policymaking” following the relatively rare event of a shark attack (generally less than one attack per million people each year) can threaten populations of the marine predators.
Noting long-term oscillations in bite rates that could be explained by climate fluctuations and factoring in human population growth, the team created a model and projected it over the next 50 years.
“This allowed us to tally the number of bites that could be avoided if people who were susceptible to being bitten were wearing good electronic deterrents properly,” says Bradshaw.
Results showed that appropriate use of the devices could avert 1063 bites on average (and potentially up to 3000). “This surprised us,” says Bradshaw, “given the low probability of being bitten – per capita – that exists even today.”
The authors note that is “a miniscule proportion (0.002%) of the population”, of which up to a third could potentially die. Their analysis relies on several assumptions including stability in shark abundance, shark behaviour and distribution (possibly influenced by climate) and human ocean use.
Based on their simulations, they say electronic deterrents could add value to other government measures to allay shark attacks. These include drones, acoustic monitoring and SMART drumlines, which alert scientists when sharks are close to shore.
It could also add to conservation of threatened species that are targeted by lethal programs, such as vulnerable white sharks and critically endangered green sawfish (Pristis zijsron), and other marine animals such as turtles and dolphins caught up in bycatch.
While the personal deterrents can lower risk of attacks – even when sharks are in predatory mode and approaching an intended prey at speed – it’s important to do your research, warns senior author Charlie Huveneers (the man who swims with sharks).
Many gadgets purporting to deter sharks are on the market but don’t necessarily live up to their promise.
“So far, scientific studies have shown that electric deterrents are the best at reducing the probability of a shark bite and that many other commercial deterrents do not have any detectable effects on shark behaviour,” says Huveneers.
“However, not all electric deterrents are equal and the public should ensure that the device they use has been scientifically tested.”
Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
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