The study adds more data to the decades-long research into shark deterrence and follows an unusually deadly year for shark bites around the world.
The study’s authors and outside shark experts were quick to stress that the findings contribute to a greater understanding of what deters sharks but it does not mean personal electronic devices are a silver bullet against their bites.
“Personal wearables are one tool in the toolbox,” said Corey Bradshaw, one of the article’s co-authors and director of the Global Ecology Laboratory at Flinders University in South Australia.
“To say 'thousands of people could avert a shark incident over the next five decades if they wear this equipment properly’ — that’s accurate within the certainty we got,” Bradshaw told The Washington Post. “But no deterrent is going to be foolproof; if you stick it on you and wear it properly, the best you can hope for is lower chance.”
Bradshaw and his team used scientific models to arrive at their projection that thousands of shark bites could be averted over the next five decades with electronic deterrence using inputs that included 120 years’ worth of existing shark-bite data, weather, climate models and population trends.
The RSOS article builds on research from 2018 where researchers tied bait to a mock surfboard and tested a white shark’s response to various deterrents such as electronic devices, magnets and a special shark-repelling wax. Bradshaw, who contributed to the 2018 study, said only the electrical devices had a measurable effect. And there’s a caveat.
“No experiment that tests deterrence is going to get the real experience down,” he said. “We can’t throw a person in a tank with a shark and see if they’ll bite.”
Globally, incidents of shark bites are low, with roughly 15 percent resulting in fatalities. According to the Florida Museum of Natural History’s International Shark Attack File, which documents shark bites, there were 57 unprovoked bites in 2020; the majority happened in the United States and Australia.
(Researchers tend to term the incidents a “shark bite” rather than “shark attack” when studying unprovoked incidents such as when someone is bitten while swimming or surfing rather than “provoked” attacks when someone is hunting, feeding or trying to touch sharks.)
Even though shark-bite incidents are relatively uncommon in most parts of the world, they occupy an outsize space in the public consciousness, thanks to frenzied coverage in the news media (and maybe the movie “Jaws”).
The raw number of bite incidents has risen over the past 30 years, but only marginally. The numbers don’t tell the whole story, said Gavin Naylor, who directs the Florida Program for Shark Research.
Shark population numbers have plummeted since the mid-80s because of hunting and fishing; at the same time, the number of people in the water has grown with the popularity of water sports such as paddleboarding, long-distance swimming and surfing.
“The number of people who have gone into the water is huge compared with the number of shark bites,” Naylor said. “You’d think there’d be four to five times as many bites.”
Oceanfront communities for a century have sought shark-mitigation efforts, relying on old-school technology such as shark nets and drum lines and even targeted culling efforts. In recent years, a push for conservation has renewed calls to end practices such as shark hunts and the use of nets, which are detrimental to not only sharks but dolphins, fish and other marine life.
With a growing number of sharks considered threatened species, an industry of nonlethal shark deterrents such as personal electronic devices has flourished in the past five to eight years, Naylor said. Manufacturers now sell personal wearables and devices that attach to surfboards and boats.
But devices on the market, he warns, provide a false sense of security if people think they can venture into risky conditions and expect not to be bitten. The best way to avoid shark bites is the common-sense guidance known for decades, he said: Don’t stray far from shore, don’t swim or surf alone, and avoid the water if conditions are rough or if there’s an abundance of bait fish nearby.
As the technology for shark-deterring wearables improves, Bradshaw said understanding how weather and climate cycles affect sharks will be another important piece of the puzzle. El Niño and La Niña weather events that can affect conditions such as flooding and water temperature in turn have an impact on algae bloom, fish populations and conditions lower in the food chain that ultimately impact an apex predator such as a shark.
“The climate signal is one of the most interesting parts; the rest is kind of just fancy math,” Bradshaw said of his recent research. “If we can give governments a tap on the shoulder and say ‘the next couple of years are going to be bad shark years,’ that can be useful.”
Bradshaw said his group’s research can hopefully contribute to the information that will steer local governments toward understanding which shark-deterrent measures work and why, so that they abandon the more harmful ones.
“Any action that actually has a positive effect [on deterrence] will allow us to get rid of things that are bad for sharks, which are a key component of the marine ecosystem,” he said, likening the removal of sharks from the water to removing lions from the Serengeti. “If you want healthy fishing, healthy oceans, you need sharks.”