Shark experts reveal reason behind Sydney’s rise in bull shark attacks

Record rain has been blamed for horrific bull shark attacks in Sydney this week, with experts urging swimmers to stay out of the water for their own safety.

Four people have been attacked in separate incidents since last Sunday, three in Sydney and one on the NSW Mid North Coast.

Experts described the sheer number of incidents as an “unprecedented” number of attacks.

Nico Antic, 12, was fatally injured after being attacked by what is believed to be a bull shark after jumping off rocks at the Hermitage Foreshore Walk near Shark Beach at Vaucluse on Sydney Harbor on Sunday, January 18.

A day later, on January 19, an 11-year-old boy had a lucky escape after being knocked off his board by a shark at Dee Why on the Northern Beaches.

The same day, 27-year-old musician Andre de Ruyter was dragged underwater while surfing at nearby Manly beach.

On Tuesday, a shark bit the surfboard of a 39-year-old man at Point Plomer, near Port Macquarie, and the surfer escaped with minor injuries.

Speaking to reporters this week, Surf Life Saving NSW chief executive Steve Pearce said the number of shark attacks over three days was “unprecedented”.

“We haven’t seen this before,” he said.

Beaches along the state’s coast have been closed while authorities try to resolve the problem, while helicopters and drones monitor for further shark activity.

“If you are thinking of going swimming, go to a local pool as we advise beaches are unsafe at this stage,” Mr Pearce said.

“That’s on everyone’s mind.

“I’ve been talking to some local surfers around here, look, they’re amazed.”

The impact of heavy rain and storms on sharks

While sharks are always present on Sydney beaches and the Harbour, last weekend’s particularly heavy rains may have triggered a shark influx.

Severe storms developed off the Illawarra, Sydney and Hunter coasts on Saturday and parts of Sunday, driven by a coastal trough, bringing the heaviest rainfall recorded for decades.

Sydney experienced its wettest January day since 1988, recording 126mm of rain on Saturday.

“In the Blue Mountains, Katoomba reported 219.8 mm, the highest rainfall recorded for January,” they said, adding records dating back to 1886.

Joel Nancarrow, owner of Fisherman and Hunter Shark Jaw Restoration, said the recent lack of rain off the coast of Sydney had encouraged bull sharks to leave rivers in large groups rather than “in smaller numbers over the months”.

“When it rains enough to keep the rivers flowing, a number of bull sharks leave the rivers; without this rain, they are all still in the rivers,” he said in a social media post.

He said the next two weeks will be crucial as smaller sharks will have to compete with larger species.

“That’s why the next two weeks are so important to be super conscious,” he warned.

“They are faster and will bite and run away, but the bite can easily be fatal.”

Sharks thrive after heavy rain

As the storms eased on Sunday, heavy rains created the perfect conditions for bull sharks to thrive.

RMIT senior research fellow Rebecca Olive said that while storms create great conditions for surfers, runoff entering the ocean “can increase the conditions that lead to shark bites”.

He explained that areas with higher stormwater runoff, such as river mouths, estuaries and stormwater drainage outlets, can encourage the emergence of more sharks.

“Water visibility is worse and waves can affect the effectiveness of shark surveillance equipment such as drones and listening buoys,” he told NewsWire.

Bull sharks are attracted to freshwater streams because they can feed on things that drift downstream, said Culum Brown, head of Macquarie University’s Fish Laboratory.

“Analysis of bull sharks caught close to shore always shows the effect of rainfall,” he said.

He explained that turbid and brackish water leads to greater presence of sharks.

“Sharks’ vision to find prey will be hindered and they will be exposed to disturbances in the water,” he said.

“They are more likely to accidentally bite a person, thinking they are prey.”

Best tips to avoid sharks

Although shark attacks are rare and the animals do not usually target humans, Professor Brown said recent rainfall and storms had increased the likelihood of sharks appearing.

“Given the incredible rainfall we’ve had recently, the risk of encountering sharks is high,” he told NewsWire.

“Do not swim after heavy rains, especially in and around estuaries.”

Professor Brown instead urged swimmers to wait until the water clears.

He also urged people to avoid swimming alone in the ocean, especially during a time when sharks are more common.

“Avoid swimming at dawn and dusk; this tends to be a time when sharks are more active,” he said.