Long-term movements of tiger sharks satellite-tagged in Shark Bay, Western Australia
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Tiger sharks are important predators in the seagrass ecosystem of Shark Bay, Australia. Although sharks appear to return to a long-term study site within the Eastern Gulf periodically, the extent of their long-term movements is not known. Five sharks fitted with satellite transmitters showed variable movement patterns. Three sharks remained within the Shark Bay region and another made a 500 km round-trip excursion to oceanic waters northwest of the bay. These four sharks showed relatively low displacement rates relative to sharks tracked over shorter time periods, suggesting that sharks move through large home ranges that include Shark Bay. Although no reliable position fixes were obtained for the fifth shark, we were able to use the timing of satellite uplinks and the position of the satellite to determine that it had moved at least 8,000 km to the coastal waters of southeast Africa in 99 days—the longest recorded movement by a tiger shark. This movement and previously documented trans-Atlantic movements suggest that tiger shark populations may mix across ocean basins and that tiger sharks are subject to anthropogenic effects at great distances from protected waters. Finally, our method for using single satellite uplinks may be useful in estimating movements for wide-ranging species that rarely provide high quality location estimates.
KeywordsSwimming Speed Location Class Syntactic Foam White Shark Satellite Telemetry
Special thanks to Graeme Hays, who suggested how we could make use of poor-quality position data. Support for this project was provided by Florida International University and by the National Science Foundation under Grant No. 0526065. The Monkey Mia Dolphin Resort and Fisheries WA provided logistical support and Greg Marshall and the National Geographic Remote Imaging Department provided a satellite tag for this study. We wish to acknowledge use of the Maptool program for analysis and graphics in this paper. Maptool is a product of SEATURTLE.ORG (information available at http://www.seaturtle.org). This study was conducted under Department of Conservation and Land Management permits SF002347 and NE001808 and renewals, Fisheries WA Permit 8/01, and Florida International University IACUC authorization. This is contribution 22 of the Shark Bay Ecosystem Research Project.
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