Sydney’s bull shark secrets on show

by Steve Whan on 2 Jun 2010
The secret life of Sydney’s bull sharks is beginning to be unlocked, with new data revealing the movement patterns of 11 tagged sharks in Sydney Harbour, NSW Primary Industries Minister, Steve Whan, said.

'This innovative Sydney Harbour Shark tagging research project from Industry & Investment (I&I) NSW forms part of the NSW Government’s efforts to minimise the risk of shark attack, by tracking the natural movements of the animals to determine any potentially dangerous areas in Sydney Harbour,' Minister Whan said.

'Significantly, results so far show that the tagged bull sharks are not associated with particular areas in Sydney Harbour, but rather travel all around its numerous tributaries and waterways, including the Parramatta River and Middle Harbour.'

'Our data provides a fascinating insight into one of the world’s most interesting shark species, and demonstrates the value of this state-of-the-art technology,' he said.

During the program, 11 Bull Sharks – all males – were captured at various locations in the Harbour in 2009/2010 and tagged with internal transmitters that have a transmitting life of up to nine years. Their movements were then recorded on a series of 45 underwater listening stations deployed throughout the Harbour and along the NSW East Coast.

Data obtained during the program shows:

• The nine male bull sharks tagged in 2010 were detected in and around the Harbour from three and up to 66 days after tagging.

• During this time, several of the sharks left the Harbour, travelled south where they were detected off Bondi, Bronte, Clovelly, Coogee and Malabar before returning to Sydney Harbour, some of the sharks were even detected as far south as Wattamolla, near the Royal National Park.

• A 2.5 m bullshark tagged west of the Harbour Bridge in March 2009 was recorded travelling more than 1000 kilometres. It was detected off South West Rocks on January 20, 2010, and was then detected in Sydney Harbour four days later. The shark stayed around the Harbour until March 11, when it travelled south to Bondi, Bronte, Clovelly, Coogee and as far south as the entrance of Botany Bay before returning to the Harbour.

'As a result of this project, the NSW Government is gaining a better understanding of the previously unknown world of these so-called man eaters,' Minister Whan said. 'The public should not be alarmed at the presence of bull sharks in the Harbour, the fact of the matter is the Harbour is their domain and sharks have been frequenting harbour waters long before bathers.

'Our last download of listening stations in late April 2010 showed that all tagged bull sharks had left Sydney Harbour. In coming months, shark researchers at I&I NSW will be investigating the factors that may be influencing the movements of the tagged bull sharks in and around Sydney Harbour including prey-movements and/or water temperature, salinity and lunar phases.

'This Government’s best shark scientists will also continue to try to catch and tag sharks during winter and spring to see if other species use the Harbour then.'

Swimmers are reminded that they can follow some simple, common sense tips to reduce their risk of an encounter with a shark.

These include:
• Not swimming at dusk and dawn
• Avoid swimming alone
• Avoid swimming when there are lots of baitfish around
• Avoid murky water

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More information can be found at www.industry.nsw.gov.au/sharksmart