Knowledge of how an animal uses its habitat is a fundamental component of effective conservation strategies. The Critically Endangered largetooth sawfish Pristis pristis uses rivers and their estuaries as nursery habitats, where it is likely to be exposed to elevated pressures from anthropogenic-induced stresses including fishing (e.g. bycatch or direct harvest) and instream habitat modification and degradation (e.g. barriers, water extraction, and mining). With a paucity of data available on habitat use of P. pristis, we monitored the movements of 32 juveniles (952 to 2510 mm total length; mean ± SE = 1919 ± 64 mm) using acoustic telemetry to explore correlations between sawfish movement and abiotic as well as biotic variables over an 8 yr period (2008 to 2015) in the freshwater reaches of the Fitzroy River, Western Australia. Monitored juveniles were least active when they occupied deeper runs and pools in proximity to large woody debris by day and were most active during night-time and twilight hours when inhabiting shallow water such as glides, pool edges, and shallow runs. These shifts in activity and habitat use were primarily mediated by foraging and refuging behaviours, which were coupled to day-night cycling of light availability. Protection of these instream habitats and the understanding of their use by P. pristis are important for aiding in the management of intermittently flowing rivers that are used as nurseries for this species.
Bibliographical noteFunding Information:
Acknowledgements. This work was supported by Murdoch University and the Western Australian Marine Science Institution and funded by Chevron Australia, the Western Australian Government’s State Natural Resource Management Program and the Department of the Environment and Energy Government of Australia. We are indebted to the Traditional Owners of the Fitzroy River and owe special thanks to the Nyingina-Mangala Rangers, Jarlmadangah Rangers, the Yiriman Project, Kimberley Land Council, Bunuba Rangers, Darngku Heritage Cruises, Bill and Mary Aitken, Department of Parks and Wildlife Western Australia, Mark Allen, Dean Thorburn and numerous other people for their assistance in the field. We thank Steve Beatty and Alan Lymbery for their insight into the statistical analyses. Gratitude also goes to Yeeda Station, Liveringa Station and Neville Poelina for providing access to their land and to Derby Mitre 10 for donating consumables for this project. We also thank the reviewers of this manuscript for their informative contributions. Finally, we thank Jim and Geral-dine Kelly for use of their facilities during field work and the people of Derby and Fitzroy Crossing for their generous support of our work. This research was conducted under Fish Resources Management Act 1994 exemptions made available by the Western Australia Department of Fisheries. Animal ethics approval of this work was provided by Murdoch University’s Ethics Board. This work was presented as part of the symposium ‘Biology and Ecology of Sawfishes’ at the 2016 annual meeting of the American Elasmobranch Society, which was supported by funding from the Save Our Seas Foundation, Disney Conservation Fund, and the American Elasmobranch Society.
© The authors 2017.
- Acoustic telemetry
- Diel activity
- Dry season
- Large woody debris