Fine scale movements and activity areas of white sharks (Carcharodon carcharias) in Mossel Bay, South Africa
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Previous work on white sharks indicate the species show seasonally limited movement patters, at certain aggregation sites small areas may play vital roles in the life history of a large amount of the population. Acoustic telemetry was used to estimate habitat use of white sharks, Carcharodon carcharias, while aggregating at Mossel Bay, South Africa. Total range of all shark tracks combined accumulated 782 h and covered an area of 93.5 km2 however, within this range, sharks were found to highly utilise a core habitat (50 % Kernel, K50) of just 1.05 km2 over a reef system adjacent to a river mouth. Individual tracks revealed additional core habitats, some of which were previously undocumented and one adjacent to a commercial harbor. Much was found to be dependent on the size of the shark, with larger sharks (>400 cm) occupying smaller activity areas than subadult (300–399 cm) and juvenile (<300 cm) conspecifics, while Index of Reuse (IOR) and Index of Shared Space (IOSS) were both found to increase with shark size. Such results provide evidence that larger white sharks are more selective in habitat use, which indicates they have greater experience within aggregation sites. Furthermore, the focused nature of foraging means spatially restricted management strategies would offer a powerful tool to aid enforcement of current protective legislation for the white shark in similar environments of limited resources and capacity.
KeywordsAcoustic telemetry Manual tracking Home range Kernel analysis Habitat use White sharks
The authors would like to sincerely thank the following. Tracking equipment was supplied by World Wildlife Fund - South Africa (WWF-SA) and National Geographic Channel, Talking Pictures and Off the Fence productions. Transmitters were supplied by Marine and Coastal Management and PADI Aware. Fuel was provided, in part, by Marine and Coastal Management (now Oceans and Coasts). One of the research vessels was donated for use by A. Hartman.
The following persons assisted in tracking (2005) J. Mourier, J. Charivas, M. Cuvier, H. Medd, A. B. Casagrande, L. Ewing, S. John, G. Horton, L. Hancke, T. Snow, S. A’bere, T. Seckler, G. Wright, C. Jurk, M. Scholl, A. Riodon. 2008–2009: S. Swanson, B. Oh, L. Brits, A. Blaison, A. Dell’Apa, J. Lang, J. Swinton, D. Zaveta, Be. Contrella, C. Graham, N. Harrison, S. Peake, J. Yee, M. Orr, L. Belleni, K. Stewart, J. Silbernagel, C. Moore, A. Johnstone, D. Edwards, A. Blessington, T. Coyne, J. Anderson, N. Tonachella, V. Cardinale, D. Uhlig, S. Lewis-Koskinen, V. Vasquez, A. Jodice, E. Teel, F. Munding, N. Julien, F. Jaine, R. G. Elliott, A. Prentice.
Special thanks to B. Oh for assisting with initial data filtering and M. Wcisel, A. Blessington and D. Delany for critique and advice on write up and presentation. Also thanks to M. Wcisel and D. Edwards for assistance with figure presentation and two anonymous reviewers for their guidance in shaping the final manuscript.
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