The study examined the movements of 43 individual juvenile white sharks, Carcharodon carcharias, in eastern Australia via satellite-linked radio tags and internally implanted long-life acoustic tags.
Between 2008 and 2015 the researchers tagged juvenile while sharks at Port Stephens in central New South Wales, and near Corner Inlet in southeast Victoria. When the sharks were tagged the researchers also recorded some physiological information, including their size and sex.
The study registered approximately 182 000 detections of acoustic-tagged white sharks on 287 receivers over seven years, with some individual sharks recorded for tracking periods of up to five years.
The data revealed complex movement patterns over distances of thousands of kilometres and 13° of latitude, with sharks ranging from the southern Great Barrier Reef, Queensland, to Tasmania, and across the Tasman sea to New Zealand.
The study detected seasonal differences to the shark movements. With sharks detected in the more northerly regions of their range in the winter-spring months, and conversely during summer-autumn months sharks were commonly detected in the southern region.
The fact that the juvenile sharks weren’t detected travelling west of the Bass Strait, confirms previous research that Australia has two distinct white shark populations. The eastern population (ranging along the coast from Tasmania to central Queensland) and the southern-western population (ranging from Western Victoria to northwestern Western Australia).
The research also found that female juvenile sharks were more commonly encountered closer to shore than males. This sex-based difference has implications for management if more females are vulnerable to coastal threats and inshore pressures.
This study highlights the importance of long-term monitoring of acoustic-tagged sharks, made possible via data sharing through collaborative national (and international) receiver arrays and the associated database created through IMOS.
Improving our understanding of the movement patterns of juvenile white sharks will inform conservation management policy, and human-shark interaction risk management strategies.
This research was conducted with the NESP Marine Biodiversity Hub, CSIRO and IMOS in collaboration with the New South Wales Department of Primary Industries. The paper ‘Broad-scale movements of juvenile white sharks (Carcharodon carcharias) in eastern Australia from acoustic and satellite telemetry’ was published on 6 June 2019 in the Marine Ecology Progress Series.