It is safe to go back in the water, at least if you wear an electronic shark repelling device. The use of such devices could prevent more than 1,000 deaths and serious injuries in Australia alone over the next 50 years, modeling suggests. Perhaps just as importantly, they could stop the panics that lead to destructive shark culls and other harmful responses.
Even in Australia, where beach-going is part of the national identity, sharks represent a tiny threat. It's frequently said that more people die in accidents driving to the beach than in shark attacks – and whether or not the numbers check out, even coastal communities lose a lot more people on the roads.
Sadly, humans are notoriously bad at assessing threats rationally. So deep is the fear of being eaten by a bloody big fish that it leads us to all sorts of bad decisions. These include destroying local economies because of a single recent shark attack, or slaughtering the apex predators key to the marine environment's health because one of their numbers bit someone. Ironically, the worst responses usually come from those with little actual shark exposure.
Many responses to shark attacks don't work, do a lot of harm, or both. So Professor Corey Bradshaw of Australia's Flinders University is keen to promote those that do, not only to save human lives but to prevent the over-reaction that so frequently follows shark attacks.
In Royal Society Open Science, Bradshaw and co-authors have modeled how much benefit would be gained from those at most risk of attack using electronic devices that interfere with the electroreception sharks use to maximize the precision of their attacks.
Many of these devices are for sale, some of which appear only marginally effective. However, Bradshaw is part of a team that previously measured one model as repelling sharks 56 percent of the time. Bradshaw admitted to IFLScience the study involved somewhat artificial conditions, with baits used to lure sharks towards unoccupied surfboards, rather than real surfers. Ethically essential as this was, it might affect the reliability of the testing, although Bradshaw thinks the true effectiveness is more likely to be higher than the estimated rate, rather than lower. Top-tier repulsion devices have sometimes scored even better in other studies.
Working on an assumption of 60 percent effectiveness, Bradshaw modeled the number of attacks that would be prevented if the devices achieve certain levels of use among those at risk of a shark attack. The paper acknowledges universal use of the deterrents will not happen, but hope as current prices of around $500 per device fall, it will become common for those most at risk to wear them.
Australia may have the reputation as shark attack central, but there are actually more deaths in the United States, though far fewer per person. Meanwhile, the island of Reunion suffered so many deaths surfing has been banned entirely. The team did not model the worldwide effects of deterrent use, but consider the Australian data indicative.