A shark expert says the risks of swimming in Sydney Harbour after heavy rainfall should have been communicated better after a shark attack left a 12-year-old boy in critical condition.
His comments came before two other shark-related incidents on Monday.
A man was critically injured by a shark at North Steyne Beach at Manly just before 6pm.
Just before lunchtime on Monday, a young surfer escaped uninjured after a shark bit off a chunk of his surfboard at Dee Why Beach in the northern beaches.
The incidents happened less than a day after a boy was left in a critical condition with injuries to both legs in a suspected bull shark attack near Vaucluse’s Shark Beach.
The boy was taken to Sydney Children’s Hospital at Randwick, where he remains in intensive care.
Northern Beaches Council said all beaches, except for Palm Beach, had been closed for swimming over the weekend due to dangerous surf conditions.
Sewage and sharks
University of Sydney associate professor of public policy Chris Pepin-Neff said swimming in Sydney Harbour after heavy rain was a “terrible idea”.
“After 20 millimetres of rain, the level of faecal matter and raw sewage that are in the harbour attracts bait fish and brings sharks toward the bait fish,” they said.
“It’s really important after a big storm to not swim in the harbour for about 72 hours.”
Dr Pepin-Neff says there needs to be better communication about the presence of sharks in the harbour after a storm. (ABC News: Isobel Roe)
Dr Pepin-Neff said flyers were posted around swimming areas to alert the public to elevated levels of bacteria, but the information did not address the risk of sharks.
“They need to put up public notices that tell people not to swim for 72 hours,” they said.
“Those are city sewerage pipes that are flowing raw sewage into the harbour, so I think the city has an obligation … to alert the public that old pipes make the harbour unsafe after a big storm.”
A 12-year-old boy was probably bitten by a bull shark at Vaucluse. (ABC)
Dr Pepin-Neff also thinks that with the combination of sewage, bait fish and murky water, the animal that bit the 12-year-old’s legs was a bull shark.
“Bull sharks are biters. They tend to bite because they’re smaller. They tend to bite more often. It’s a bad recipe if you’re in the water,” they said.
‘There’ll be more’
Marine Life Rangers founder David Baxter said there were more migratory species like bull sharks in the harbour because of the temperature of the water.
“They’re cruising up and down our breaches,” he said.
“We know [in] the harbour, for example, we’ve got dirty water, then overcast rain, a lot of the run-offs from the creeks and the drains, and that it stimulates the curiosity of sharks.
Mr Baxter says he expects more shark attacks within the harbour. (ABC News)
“We’ve had those two attacks in the harbour, and I’m predicting that there’ll be more.”
Mr Baxter urged people to be cautious.
“If it doesn’t feel right, the conditions aren’t right, just don’t go in,” he said.
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In a statement on Monday afternoon, the NSW Department of Primary Industries and Regional Development (DPIRD) said a bull shark most likely attacked the 12-year-old.
“DPIRD shark scientists are unable to definitively confirm the species based on photos of the injury. However, they believe a bull shark was likely responsible based on the nature of the injuries and the environmental conditions at the site,” it said.
“Water conditions in the harbour are brackish following heavy rain and runoff, which can worsen visibility.Â
“Advice from experts is to avoid swimming in low visibility, murky water.”
The 12-year-old boy had jumped off rocks at Shark Beach before a shark attacked him. (ABC News: Isobel Roe)
Marine Area Command commander, Superintendent Joseph McNulty, said on Monday that heavy rainfall may have contributed to the attack at Vaucluse.
“We believe the combination of the brackish water, the fresh water, and the actions of the splashing may have made that perfect storm environment for that shark attack yesterday,” he said.
Sydney experienced its wettest day since 1988 on Sunday, with the city’s official weather station at Observatory Hill recording 127mm of rain in 24 hours.Â