After another swimmer was seriously harmed by a shark on Saturday, this time at Sydney’s Coogee Beach, Australians are increasingly paying attention to the risks that the animals may pose. There is no doubt that the rate of shark encounters with humans is rising, but it is not entirely clear why. The bigger question is how best to reduce shark bites.
Human shark interactions involve two parties: people and sharks. We need to manage both. There is no doubt that there are more people in the water year-round, which alone accounts for most of the increase in encounters.
Here we are in June and the water temperature around Sydney is still between 18 and 19 degrees – pretty comfortable for most water sports if you’re wearing a shorty westsuit. There are still a lot of people in the water, even though it is winter. Saturday was gloriously sunny, after all.
Less known is the impact of climate change on the behaviour of sharks, although it is clear their distributions are shifting on a broader scale. Most sharks try to maintain a comfortable thermal envelope because, unlike mammals that generate their own heat, a shark’s body temperature is determined by the temperature of the water. White sharks prefer it on the cool side (15 to 22 degrees), whereas bull sharks like the warmer waters (22 to 28). So climate change is causing shifts in human and shark behaviour, which adds to the unpredictability and will require some rethinking about how best to manage this conflict.
We often hear in the media and elsewhere that shark numbers are on the rise. For the most part, scientific evidence simply doesn’t support this. The top three species that are the target of management in Australia (whites, bulls and tigers) are all listed for protection because their numbers are declining. Respectively, they are vulnerable, vulnerable and near threatened, according to the International Union for Conservation of Nature.
So a sensible management approach must be one that enables us to live alongside these animals without placing them (or us) at further risk.
We also need to be far more aware of the actual risk that sharks pose to people. The death rate from shark bites is about two to three people per year in Australia. The long-term trend is increasing slightly, but it is a very patchy data set. Some years we have no fatalities and the next there will be a cluster. Nonetheless, the risk is extremely low considering that there are millions of Australians in the sea year-round.
The risk is so low, in fact, that it is worth questioning just how much money we invest in managing the perceived “shark threat”. Most of the fatalities are surfers or spearfishers. To some extent, it is a numbers game; the more time you spend in the water, the more likely you are to encounter a shark. But if bitten, the key thing that determines survival is how quickly the victim receives help. That help was immediate and life-saving for the swimmer at Coogee on Saturday.
It should be noted that sharks do not eat people, but they do sometimes bite either out of self-defence, mistaken identity or curiosity.
One thing that is clear is that we need to transition from age-old approaches – mostly nets and drum lines, which have largely aimed to reduce shark numbers – towards enabling our co-existence with sharks. Drones will play an important role, but we have grossly underutilised this technology to date.
A ban on drones at Coogee because it is in the flightpath for commercial airlines was temporarily lifted on Sunday to allow Surf Life Saving NSW to scan the area for sharks. But we live in the AI era, where drones can be programmed to fly solo and automatically track and recognise sharks. They can report back to a ground station and sound alarms to call people out of the water. They could even recruit other drones to chaperone water users back to shore. This is where the future lies. Yes, there are some concerns regarding where drones can fly, but it is highly unlikely that they pose a serious risk to commercial aircraft if flown at low levels. Some of that legislation needs revisiting.
Shark nets catch almost no target species and indiscriminately kill non-target threatened species, such as whales, dolphins and turtles. The bycatch outweighs the target catch by at least tenfold. To put it succinctly, the environmental impact of nets is far too great and the benefits are almost non-existent. Analysis suggests that nets do not significantly improve safety at beaches.
NSW is transitioning from drum lines – where baited hooks tended to trap and drown sharks – to smart drum lines, which raise an alert when sharks are hooked, allowing for them to be released with a tag, unless they are already tagged. Many are. The survival rate of sharks in the smartline captures is much greater, and the broader ecological impact is significantly reduced. Reports from the NSW Department of Primary Industries show that smart drumlines and drones are far more effective at detecting the three target shark species. The state government is rightfully investing in this approach.
We are also making good progress on personal deterrents. Some of the technology that produces electromagnetic fields around the swimmer or surfer does deter sharks to varying degrees. There are other efforts to reduce accidental bites by lighting up the underside of surfboards to break up the silhouette.
More investment is needed to understand shark behaviour and why sharks bite people, so we can come up with effective targeted solutions. Some of those solutions are staring us in the face; we just need to embrace them.
Professor Culum Brown is the head of the Fish Lab at Macquarie University.
Professor Culum Brown is the head of the Fish Lab at Macquarie University.From our partners
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