Abundance, site fidelity and range patterns of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in two Australian subtropical estuaries
Christine A. Fury A B and Peter L. Harrison AA Southern Cross University Whale Research Centre, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia.
B Corresponding author. Email: cfury@scu.edu.au
Marine and Freshwater Research 59(11) 1015-1027 https://doi.org/10.1071/MF08109
Submitted: 4 April 2008 Accepted: 1 September 2008 Published: 27 November 2008
Abstract
Bottlenose dolphins are widely studied in marine habitats, but information on estuarine populations is very limited. The present study provides the first published data on bottlenose dolphins in Australian estuaries. Abundance estimates, site fidelity and individual ranging patterns were examined over a 3-year period for Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabiting the Clarence River (CR) and Richmond River (RR) estuaries in northern New South Wales, Australia. Mark–recapture analyses estimated 71 (62–81 95% CI) dolphins utilised the CR whereas 34 (19–49 95% CI) used the RR. Differences in site fidelity were observed between the estuaries, with 60% and 37% of identified dolphins determined as residents, 26% and 21% as occasional visitors and 14% and 42% as transients for the CR and RR respectively. Resource partitioning was apparent in both estuaries with the mean distance resident dolphins were found upstream from the river mouth being greater than occasional visitors and transients. The Clarence River sustains a larger, predominantly resident dolphin community compared with the Richmond River, which supports a relatively small dolphin community with lower site fidelity. Management of future increased anthropogenic disturbances is needed to ensure the long-term survival of these dolphin populations.
Additional keywords: closed population, estuary, population size, ranging patterns, residency patterns.
Acknowledgements
We thank Marjolijn van Stokkom, Kelly Toms, Paul Kelly, Daniele Cagnazzi, Kim Stewart, Kate Sprogis and Nicole Patten for assistance with field work, Greg Luker for GIS advice and Lyndon Brooks for statistical advice. We also thank Professor Andrew Boulton, Associate Professor Manuel dos Santos, Dr Simon Ingram and an anonymous reviewer for invaluable comments on the manuscript. This study was funded by Australian Geographic, Angourie Rainforest Resort, Project Aware and Southern Cross University Whale Research Centre. Field work was done under permit from the New South Wales Parks and Wildlife Service and ethics approval from Southern Cross University (NPWS S10404 and SCU no. 05/15).
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