Oral Presentation Australian Society for Fish Biology Conference 2017

Broad-scale movements of white sharks in eastern Australia from acoustic and satellite telemetry (#92)

Barry Bruce 1 , David Harasti 2 , Kate Lee 2 , Christopher Gallen 2 , Rebecca Bradford 1
  1. CSIRO Oceans & Atmosphere, Hobart, TASMANIA, Australia
  2. Fisheries Research, NSW Department of Primary Industries, Nelson Bay, NSW, Australia

The advent of electronic tagging has seen vast advances in our understanding of marine top-order predator movements over broad spatial scales. However, most studies are restricted to relatively short temporal scales. Recent improvements in battery life, combined with the surgical implantation of acoustic tags, has increased the opportunity to examine movements over time periods relevant to ontogenetic changes and at scales providing context to interannual variability. Herein we examine data from 43 juvenile white sharks (1.7 to 3.2 m Total Length) tagged with long-life acoustic tags and monitored by receiver arrays spanning a continental-scale and across international boundaries. The study registered approximately 182,000 detections of tagged white sharks on 287 receivers over seven years, with individual tracking periods of up to five years. We compare these to satellite tracking data collected on the same sharks over the same period. Data reveal complex movement patterns throughout the eastern Australian region over distances of thousands of kilometres with sharks ranging from the southern Great Barrier Reef, Queensland, to Tasmania and across the Tasman Sea to New Zealand. Juvenile white sharks showed a variety of movement patterns including annual fidelity to spatially restricted nursery areas in central NSW and southeast Victoria, directed seasonal coastal movements, intermittent areas of nearshore temporary residency and offshore excursions. Data support restricted movements of juveniles east and west of central Bass Strait further supporting a two-population model for the species in Australian waters. Female sharks were more commonly encountered in inshore waters than males and their latitudinal movements were more extensive. The data highlight the value of broad-scale, nationally and internationally collaborative acoustic receiver arrays and sustained monitoring of individual sharks over multi-year time periods.