UP to 250 juvenile great white sharks are living off the Hunter coast and spending a lot of time around beaches in water depths of one to five metres, CSIRO research shows.
Tagged great whites have been tracked swimming along the coast from Lake Macquarie to Seal Rocks, maps show.
These sharks were ‘‘abundant along a section of coastal waters in the Port Stephens region’’ from about September to January each year, a CSIRO report said.
Sharks were residents ‘‘specifically along three beaches’’ – northern Stockton, Bennetts beach (Hawks Nest) and Mungo Brush, north and south of the Port Stephens estuary.
Satellite tracking showed juvenile white pointers occupied habitat in the Port Stephens area from close to shore to 120-metre-deep water.
The nursery area ‘‘extends up to 25kilometres offshore’’.
‘‘They spend a significant amount of time in the surf zone in water depths of one to five metres, where they are readily observable and frequently encountered by the public,’’ the report said.
Research in 2010-11, based on tagging and monitoring at Bennetts beach, estimated the sharks spent ‘‘an average of 36.5per cent’’ of their time off Port Stephens in ‘‘near-shore waters including the surf zone’’.
In 2012-13, great whites were recorded spending 20per cent of their time ‘‘near to the surf zone of Bennetts beach’’.
A CSIRO statement said the ‘‘frequency of encounters between people and sharks can be high’’ in the area, but the frequency of attacks was ‘‘very low’’.
Surf lifesavers said attacks off the Port Stephens coast were rare, but there had been two recent attacks in the bay – off Jimmys beach.
CSIRO research showed the the bay area, including the Halifax Point and Jimmys beach areas, were ‘‘more commonly used by juvenile white sharks than previously thought’’.
‘‘Several tagged sharks spent relatively short but significant periods inside Port Stephens estuary [the bay],’’ the report said.
‘‘Sharks were frequently detected on the northern side of the bay in the vicinity of Jimmys beach.’’
CSIRO scientist and shark researcher Barry Bruce said the objectives of the research, which ran from 2007 to 2013, were to ‘‘determine the survival rate of juveniles and adults and provide estimates of abundance of juveniles’’.
‘‘This study provides further confirmation the Port Stephens region is a key nursery area for juvenile white sharks in eastern Australia,’’ the CSIRO report said.
The CSIRO said a new project this year would develop techniques for ‘‘a population assessment’’ for great white sharks.
‘‘An assessment is necessary to understand whether the species is recovering,’’ a statement said.
‘‘The project will advance efforts to halt the decline of marine biodiversity through supporting the recovery of a threatened species, the [great] white shark.’’
Tag For Life’s Kent Stannard, who works on the project, said on his website it would ‘‘focus on the inner coastal waters around Port Stephens, where the CSIRO have been tagging white sharks for the past seven years’’.
‘‘This area has been known to scientists for some time as a nursery for juvenile white sharks, but it has only recently come to light as being the preferred habitat for newborns,’’ Mr Stannard said.
‘‘The aim of Tag For Life is to communicate scientifically supported information that will lead to the establishment of a safer coastal environment for boardriding, swimming, diving and fishing communities.
‘‘Many of us have a healthy respect and fascination for the white shark.’’
The CSIRO program involved tagging great whites and aerial surveys.
It included regular surveys of juvenile great whites in surf zones between Seal Rocks and Newcastle.
Sharks in this area were usually 1.8metres to 2.6metres in length, but some were up to 3.5-metres long.
The sharks commonly departed the Port Stephens area from December to January, generally swimming south to eastern Bass Strait, where they resided until April.
Electronic tagging studies had pinpointed two nursery areas for juvenile great whites in eastern Australia – Port Stephens and the Ninety Mile beach and Corner Inlet region of eastern Victoria.
‘‘The more accessible of these two sites is a 50-kilometre to 60-kilometre stretch of coastline centred in the Port Stephens area,’’ the CSIRO report said.
A total of 44 juvenile white sharks were tagged from 2007 to 2012 at Stockton and Bennetts beaches.
An independent animal ethics committee approved capture, handling and tagging procedures.
The reason why juvenile great whites are attracted to Port Stephens is unclear, but experts believe it could be a plentiful supply of fish and sharks feeling it’s a prime area for survival.
About the CSIRO map
This CSIRO map shows satellite tracking of great white sharks off the Hunter coast from 2007 to 2011
The movements of each shark is colour-coded
The map shows a pattern of temporary residency off Port Stephens
The mean estimated residency period in the nursery area was about 70 days
During this period of residency, sharks occupied various habitats including deeper areas out to mid-shelf depths, islands, inside the Port Stephens estuary and in the surf zone
Juvenile white sharks aggregate in the Port Stephens region from early spring to mid-summer, although sharks may be encountered at any time of year
The footprint of the nursery area covers 50 to 60 kilometres of coast from Stockton Beach, south of Port Stephens, to Mungo Brush in the north
The footprint of the nursery area extends from one-metre deep areas of the shore to 25 kilometres offshore in 120-metre deep water
The Port Stephens nursery area is used primarily by juveniles between one and five years of age
Sharks remain resident for weeks to months specifically along three beaches: northern Stockton, Bennetts beach [Hawks Nest] and Mungo Brush
Acoustic monitoring shows juvenile white sharks are resident to the nursery area for periods from September to February
Sharks most commonly depart the nursery from December to January
Departure is not co-ordinated, with individuals leaving over an extended period
When sharks leave the area, they generally move in a direct fashion and south to the Corner Inlet and Lakes Entrance region of eastern Bass Strait where they reside from late December to April
In some cases, tagged sharks have travelled north as far as the Great Barrier Reef and New Zealand
Satellite tracking and aerial surveys confirm juvenile white sharks are more abundant in coastal waters of Port Stephens, than areas north or south
Some sharks may temporarily leave the nursery area for a few days, before returning, prior to their seasonal departure south
Sharks were present off Port Stephens beaches over a wide range of temperature conditions
The Port Stephens nursery area provides some of the most significant habitat for juvenile white sharks in eastern Australia.