Sydney is still reeling from a shock shark attack that left a popular surfer dead.
Mercury Psillakis, 57, was killed while surfing off Long Reef Beach in Dee Why on Sydney's Northern Beaches on Saturday.
It was the second fatal attack in Sydney in three years, after diving instructor Simon Nellist was killed while swimming near Little Bay in February 2022.
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The deadly attack has sparked debate about shark nets and the strategies used to minimise the risks for oceangoers.
What happened in the Long Reef attack?
Emergency services were called to Long Reef Beach after 10am on Saturday after reports of a shark attack.
Mercury Psillakis reportedly spotted the predator and attempted to warn other surfers before he was attacked.
Psillakis suffered catastrophic injuries and lost several limbs, and was unable to be revived when he was brought to the shore.
Long Reef and Dee Why Beaches were subsequently closed after the attack.
What type of shark attacked Mercury Psillakis?
Experts believe Psillakis was attacked by a great white shark.
"NSW government shark biologists have assessed photographs of the victim's surfboard and determined a white shark approximately 3.4-3.6 metres in length was likely responsible," a NSW Department of Primary Industries and Regional Development (DPIRD) statement said yesterday.
"Based on information from emergency services, it is understood the incident occurred approximately 300 metres north of the Surf Life Saving club."
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Are shark attacks on the rise?
Shark bites and attacks are extremely rare but have increased over the past decade.
The last fatal attack in Sydney occurred in 2022 and before that, you have to go back to the 1960s to find the last recorded fatal bite.
There are an average of 20 shark incidents each year in Australia that cause injury, with an average of 2.8 fatalities over the past 10 years, according to the Australian Shark Incident Database from the Taronga Conservation Society Australia.
In 2023, there were four fatal shark bites in Australia.
Professor Charlie Huveneers from Flinders University said the global risk had increased but varied among regions.
"Globally, the number of shark bites has increased over the past four decades," he said.
"However, shark bites are decreasing in some regions and remain stable in others, reflecting the high variability of the risk of being bitten by a shark."
Huveneers' team found 40 factors that can contribute to an increased risk of shark attacks.
"Human population growth, habitat modification and destruction, declining water quality, climate change and anomalous weather patterns, and changes to the distribution and abundance of sharks and their prey are all often proposed to explain the recent increases in shark bites," he said.
He said a combination of those factors could increase the risk, but a lack of consensus in research made it difficult to pinpoint the effects of each.
Did Dee Why have shark nets?
There is a shark net at Dee Why.
It is about 500 metres from the shore, with the nets being 150 metres long and six metres deep.
As a result of the weekend's attack, new measures have been taken, including adding two extra SMART drumlines in addition to the three already deployed in the area.
The NSW government also announced a pause to the trial removal of shark nets in various locations around Sydney beaches.
Do shark nets work? Are they effective?
While shark nets are a common tactic to deter sharks from attacking around the world, experts are unconvinced about their effectiveness.
"The pause in the trial of the removal of shark nets is unfortunate as shark nets are not an effective mitigation approach, and can actually provide ocean users with false security that they are being protected from bites," Dr Brianna Le Busque from the University of South Australia said.
"People fear things that we feel we can't control, and non-effective mitigation techniques like nets can make people inaccurately feel in control of shark interactions."
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How are shark nets bad for the environment?
There are concerns about the negative effects shark nets and drumlines can have on sharks and other animals.
Experts say other animals can often become caught in nets and drumlines, causing injury or death.
"Decades of research show that these measures have not been proven effective at preventing bites," Dr Lucille Chapuis from La Trobe University said.
"Nets and drumlines can also act as attractants, entangling sharks and other marine life, including turtles, dolphins, and rays."
Are there better alternatives to shark nets?
Chapuis believes modern technology needs to be embraced to better protect against shark attacks while also avoiding damage to the ecosystem.
"Non-lethal technologies such as drone surveillance and personal deterrents offer more promising approaches," she said.
"Sharks are vital top predators, and removing them indiscriminately can have significant ecological impacts."
Huveneers said new strategies are being shared and implemented, centred on developing a perimeter and proximity from sharks, while also wearing wetsuits that are bite-resistant and prevent bleeding.
"Commercially available products like personal electronic deterrents can overwhelm a shark's sensory organs and reduce the risk of bites by up to 60 per cent even when sharks are in a predatory mode," he said.
"Establishing an outer ring of measures to maximise the space and reduce overlap between water users and sharks [can help].
"These include swimming enclosures to separate people and sharks, beach meshing, SMART or traditional drumlines, aerial surveillance, and tagged-shark listening stations."
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