Drones and drumlines: can Australian seas ever be safe from shark attacks?

Already in 2020, five Australians have been tragically killed after being bitten by sharks in what looks set to be a year of higher than usual deaths from the ocean predators.

Two surfers, a scuba diver, a spearfisher and a swimmer have all died from injuries caused by shark bites.

On Friday, a 10-year-old boy was pulled from a boat by a shark in north-west Tasmania. Ambulance Tasmania said the boy suffered cuts but was stable. The boy’s father had jumped into the water to help, and the shark swam away.

According to the Australian Shark Attack File, maintained by Taronga Conservation Society, Tasmania had not experienced an injury from a shark since 2012.

Across the country in 2019 there were 10 injuries from unprovoked shark bites, and no fatalities. Over the most recent five-year period, Australia averages 16 unprovoked shark incidents each year.

According to a report from Royal Life Saving Australia, these numbers compare to 94 drowning deaths at Australian beaches and harbours between July 2018 and June 2019.

Are shark attacks on the rise?

The Australian shark attack file is affiliated with the Florida Museum of Natural History’s shark research program – the base for the International Shark Attack File that investigates and records unprovoked shark bites around the world.

Dr Gavin Naylor, the museum’s shark program director, says Australia has seen only a slight increase in the number of unprovoked bites over the past 20 years.

“This may be a consequence of people better documenting incidents and reporting them. The number of fatalities in Australia oscillates from year to year, and shows no detectable trend,” he says.

Generally, Naylor says, the obvious point held true that the more people there are in the ocean, the more likelihood there would be of bites occurring.

Shark swimming in the ocean

Bull sharks are present in Sydney harbour throughout summer but attacks are rare. Photograph: Armando F Jenik/Getty Images

Australia’s love of water sports is one reason why the nation tends to record more fatalities than most other countries. The fact that great white sharks are present in the same places that are popular with surfers is also a factor, he says.

But the lack of any real trend in shark bites (at a time when human population is increasing) doesn’t mean that conditions under the waves are not changing from the perspective of the sharks.

Dr George Roff, an ecologist at the University of Queensland, says: “It’s incredibly challenging to get a handle on shark populations.

“There’s an issue of the shifting baseline where surfers might say they see a lot of sharks, but are they seeing more than their parents or grandparents did?”

When it comes to sharks that bite humans, the species of most concern are great white sharks, tiger sharks and bull sharks.

Roff led a study in 2018 that analysed the sharks caught on the hooks of the Queensland Government’s shark control program over the past 55 years.

The numbers of great white, tiger, hammerhead and whaler sharks had dropped by between 74% and 92%, according to the catch data.

Roff says while logic would suggest more people in the ocean equated to more bites, there is little data to support that idea.

With the advent of camera drones being used close to beaches, footage shared publicly on social media platforms shows how disinterested sharks often are in humans in the water.

‘Healthy oceans need sharks’

Roff identified another problem of looking at sharks and their relationship with humans through the lens of statistics and bites.

“People might have data on a small number [of bites] but you can’t use that to model the negatives – we don’t think about all the people in the water that are not bitten.”

Shark spotting: how a drone app is helping to keep Sydney’s surfers safe in the water – video

Analysis of data from the NSW government’s shark net program for a study published in October 2019 suggests the numbers of great white, tiger and whaler sharks being hooked has also dropped in NSW waters.

Prof Rob Harcourt, of Macquarie University in Sydney, is currently researching sharks along the east coast of Australia.

Knowing how many sharks there are in the water is difficult, he says. They’re a highly mobile creature.

Even studies that have used data from shark control programs are open to interpretation because, he says, if ocean temperatures are changing, this could be influencing the shark’s movement relative to the fixed locations of the government-sanctioned hooks. So less or more sharks being hooked, may not mean there are more or less sharks on the water.

In May, Harcourt was a co-author of a study that analysed data on the whereabouts of bull sharks, using commercial fishing catch data and information from the NSW government’s shark mesh program.

Bull sharks have a preferred temperature range and tend not to like temperatures cooler than 21C, putting some places along the NSW coast out of bounds.

But warming of ocean temperatures is already making conditions more favourable for these sharks. “We know that the water temperatures are changing, and that’s changing their distribution,” Harcourt says.

By 2030, the research suggests, further warming of the waters along the NSW coast will give bull sharks an extra three months of favourable water temperatures.

Bull sharks spend their first five or six years in and around estuaries where they’re born and Harcourt says there is evidence that those places, too, are getting warmer.

In April, a study found estuaries along 1,100 kilometres of the NSW coast had warmed by more than 2C between 2007 and 2019.

Harcourt says there are two reasons why sharks bite people.

Either the shark is looking for food and the bite will be severe, or they are biting with less force as a way to investigate what’s in the water.

“Sharks don’t have hands, so they’ll also mouth gently and that’s probably investigative behaviour. If it’s going for food, then the bite is not the shark making a mistake.”

Shark tagging in NSW, Harcourt says, shows clearly that “bull sharks go everywhere in Sydney harbour and they’re present right through the summer, yet we very, very rarely get an attack”.

Dr Leonardo Guida, a campaigner and shark scientist at the Australian Marine Conservation Society, told Guardian Australia: “Sharks are incredibly important to marine ecosystems – without sharks, those ecosystems can become unbalanced.”

He says commercial fishing is the main threat to shark numbers, but government programs to catch sharks on drumline hooks are “pressure that they don’t need”.

“News of a shark bite is news nobody ever wants to hear, let alone experience. But we do also have to understand that when we enter the water, it’s a big blue wilderness. Healthy oceans need sharks.”

Making the ocean safe

Earlier this month, the New South Wales government announced it was spending $8m as part of a new strategy that would include deploying drones across 34 beaches. The state also has 21 shark detection stations and shark meshing on 51 beaches between Newcastle and Wollongong.

Hammerhead shark in the ocean

‘Shark attacks are a tragedy and we should be doing more to address those, but the answers are not drumlines and nets,’ ecologist George Roff says. Photograph: BIOSPHOTO/Alamy Stock Photo

The state already has 35 smart drumlines fixed with monitors that alert fisheries contractors when a shark is hooked, in theory allowing them to arrive and release the sharks.

Guida says there needs to be a suite of approaches to improve beach safety, but there is no silver bullet. Smart drumlines were a step forward, but they still harmed the shark. Drones to warn swimmers, shark deterrent technologies and community education was the answer, Guida said.

“We need community education on how sharks move around and that has to be fundamental to any strategy.”

Queensland and NSW governments have a list of advice to bathers to reduce the risk of being bitten by sharks.

Bathers should swim on patrolled beaches, avoid swimming at dawn and dusk or swimming in murky water or places where fish have been cleaned or baits have been discarded. The use of shark deterrent technologies is also recommended. In WA, the government offers rebates on some devices.

George Roff adds: “Shark attacks are a tragedy and we should be doing more to address those, but the answers are not drumlines and nets.

“We should be using drone technology and trying to understand shark movements.”


Leave a Reply

This website uses cookies. By continuing to use this site, you accept our use of cookies.