The death of a surfer in a shark attack on one of Sydney’s northern beaches has reopened debate about the use of shark nets at Australian beaches.
Mercury Psillakis, 57, was surfing at Long Reef on Saturday when he was attacked by a large shark just a week after the annual installation of shark nets across the NSW coast.
His death has led to the suspension of a trial to remove nets from some beaches. On Tuesday, the NSW government confirmed no shark nets will be removed this summer.
The NSW Department of Primary Industries (DPI), responsible for shark nets in the state, has assessed photographs of Psillakis’s surfboard and determined a 3.4 to 3.6 metre white shark was likely responsible.
Long Reef is adjoined to the south by Dee Why, which does have a net – although contrary to popular belief, shark nets are not a complete barrier to entry to the waters used by swimmers and surfers.
So how exactly do shark nets work? How effective are they? And what does last weekend’s tragedy mean for the NSW government’s trial to remove the nets in favour of modern safety measures?
How do shark nets work?
Shark nets are now a “very old” technology, says Robert Harcourt, emeritus professor of marine ecology at Macquarie University, with the first recorded net used at Coogee Beach in 1922 after a fatal attack.
The NSW Department of Fisheries began to introduce them statewide in 1937, with the program since expanded to include 51 beaches (typically one net at each beach) between Newcastle and Wollongong.
The nets do not enclose an entire beach. They are usually 100 to 150 metres long and typically placed about 500 metres from the shore.
The nets, which are anchored by a weight to the ocean’s floor, are about six metres in height and sit about four metres below the water’s surface, with a gap of a couple of metres underneath. It means sharks are free to swim over, under and around the net. About 40% of sharks ensnared have approached from the beach side.
Shark nets sit below the surface of the water and are a deterrent – but not a complete barrier. Illustration: Sharksmart/DPI/NSW Department of Primary Industries
Harcourt says they are, essentially, a form of fishing. Through their use of gillnet, a diamond-shaped mesh common in the fishing industry, they aim to catch at least some of the local shark population swimming through the area, in theory leading to a reduction of the risk of shark attacks.
Nets are checked every few days, and alive sharks are tagged and released – although Harcourt says gillnets are “intended to kill”. “They’re likely to catch whatever’s coming in or out of the bay,” he says.
In the case of NSW shark nets, the mesh is about 60cm by 60cm, meaning it can ensnare sharks of more than 2 metres in length, including white, bull and tiger sharks – the “target sharks” most responsible for attacks and deaths.
The nets are deployed in the warmer months between 1 September and 31 March every year.
Modern nets now have alarms and “pingers” fitted to deter marine mammals, including whales, dolphins and turtles, although Harcourt says these are not that effective – more on that later.
How effective are shark nets?
Dr Leonardo Guida, an Australian Marine Conservation Society shark scientist and campaigner, likens a shark net to trying to stop flies with “a screen door with mesh as wide as your thumb”.
Studies show they may slightly reduce – or have no impact – on attacks.
Harcourt says part of the problem is that shark attacks are so rare that “it is impossible to tell the difference” with statistics at the same beach with and without a net.
In the last 10 years, an average of 20 people were injured nationwide and 2.8 people killed in shark incidents each year, according to the Australian shark incident database. The last fatal attack in Sydney occurred in February 2022 and the last known fatal attack on the northern beaches was at North Narrabeen, about 90 years ago.
A spokesperson for the DPI said the 150-metre net at Dee Why beach is towards the southern end of the beach (the entire Dee Why-Long Reef beach extends for 1.8km) – about 500 metres out from the Dee Why surf life saving club.
They said it was thought Saturday’s incident occurred approximately 300 metres north of the club.
A Baby humpback whale that became entangled in shark nets around the Gold Coast in 2018. Photograph: Nicole McLachlan/Humane Society International/Australian Marine Conservation Society
Some experts believe shark nets may actually attract sharks towards other dying marine animals caught in them. In 2024, 90% of animals caught were non-target species, of which more than half – 134 animals – were killed.
Guida says they catch “an inordinate number” of “rays, turtles, dolphins – seals, in some instances”.
Harcourt describes shark nets as a “wicked problem”. “[They] are targeted at dangerous sharks … but white sharks themselves are also listed as endangered, so we have to put in place measures to try and reduce mortality.”
Why was the government planning to trial their removal?
After this weekend’s tragedy, the NSW government has paused a trial to remove shark nets.
Three councils, including the Central Coast, Northern Beaches (which covers Dee Why) and Waverley (which includes Bondi and Bronte), had been asked to nominate a beach to trial the removal of nets. On Sunday the premier, Chris Minns, said the trial had been put on hold until a report into Saturday’s attack was handed down.
On Tuesday, the primary industries minister Tara Moriarty confirmed no shark nets would be removed as part of a trial this summer.
One of the arguments for the trial is that shark nets have been bolstered by newer non-lethal mitigation techniques, including SMART drumlines – a form of baited trap with caught sharks tagged and released – and drones to visually monitor beaches.
In 2023-24, smart drumlines in NSW caught 413 target sharks, the drones detected 362 and listening stations 473, compared to the 15 target sharks caught in nets that year.
A DPI spokesperson said two additional drumlines had been deployed between Dee Why and Long Reef in addition to the three deployed daily off Dee Why all year round.
Surf Life Saving NSW also deployed drones in the area again this week; the normal drone program for spring starts on 27 September.
Prior to Saturday’s attack, the three councils had all expressed their willingness to trial the removal of nets. But speaking this week, the Northern Beaches mayor, Sue Heins, told Guardian Australia it would now await the result of the report.
“The whole community is in mourning,” she says. “We are keen to understand if there’s any more information as to what could have been done.”