Locations where sharks have been captured and tagged, then released in Sydney’s waterways, have been revealed following an attack in the city’s eastern suburbs on Monday.
Lauren O’Neill, 29, was bitten on the leg while swimming near an Elizabeth Bay jetty at dusk on Monday.
The shark was most likely a bull shark, NSW Department of Primary Industries (DPI) shark scientist Dr Amy Smoothey said.
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“Based on our tagging and tracking research, we know that bull sharks are more numerous in the Sydney Harbour and in our coastal waters of NSW in summer and autumn,” she said.
“Specifically, in January and February, bull shark numbers are at their highest in Sydney Harbour.”
The sharks make the journey to Sydney from Queensland every summer to hunt for fish, and will head back up north when temperatures start to drop.
DPI has tagged 264 bull sharks since 2009, with 87 of those located in Sydney Harbour.
“These sharks have ranged in size from 2m to 3.2m in total length,” Smoothey said.
Sharks have been located and tagged at Kirribilli, Garden Island and the Opera House, as well as further up the Parramatta River near Glades Bay.
The tags fixed to these sharks have 10-year-long batteries and have given researchers the ability to track their movements long-term.
“Based on this tagging and tracking study, we’ve found that bull sharks utilise the entire stretch of the waterways,” Smoothey said.
“They utilise the entire stretch of the waterway from the harbour entrance to the river region of the Parramatta, Lang Cove River and Middle Harbour.”
Bull sharks can travel large distances in a short period of time, and the tracking study has documented this in Sydney’s waterways, Smoothey said.
This means locations where sharks have been sighted or tagged cannot be labelled as hot spots for the animals.
The shark in Monday’s attack is also unlikely to have remained in the area, Smoothey said.
The beach-focused SharkSmart alert system has detected and tagged eight bull sharks off Sydney’s beaches in the past week.
The community has been urged not to panic following Monday’s incident.
“It’s an extremely rare event,” Macquarie University Professor Culum Brown said.
“We have to bear in mind the last time we had a shark bite fatality in Sydney Harbour was 1963.
“There have been maybe five incidents in the last 60 years.”
Bull sharks are not particularly aggressive and higher bite incidents may be attributed to their presence in areas where there are “always people”, Brown said.
The recent rain may have contributed to the sharks moving in to the area hoping for food, he said.
“They also tend to be more active in the evening,” Brown said.
“Definitely, swimming at night by yourself after rainfall would be not a good idea.”
For bull sharks in Sydney Harbour, from about 6pm until about 1am is the peak activity time, Brown said.