Seasonal use of a macrotidal estuary by the endangered dwarf sawfish, Pristis clavata

David L. Morgan, Karissa O. Lear, Emma Dobinson, Adrian C. Gleiss, Travis Fazeldean, Richard D. Pillans, Stephen J. Beatty, Jeff M. Whitty

Research output: Contribution to journalArticlepeer-review

Abstract

Sawfishes (Family: Pristidae) are one of the most imperilled fish families worldwide. There is an increasingly urgent need to better understand the biology, ecology, and population status of the five sawfish species to develop more effective conservation measures. The dwarf sawfish, Pristis clavata, is one of the least researched members of the pristids, with literature limited to analysing disparate datasets or collations of rare encounters in northern Australia. This study examined the spatial ecology of dwarf sawfish using targeted surveys and acoustic telemetry to determine its habitat use in a macrotidal estuary in northern Australia. Seventeen dwarf sawfish were tagged with acoustic transmitters and monitored in the Fitzroy River estuary and adjacent King Sound (Kimberley, Western Australia) between August 2015 and November 2017. Dwarf sawfish observed within the Fitzroy River estuary and King Sound were juveniles, ranging between 740 and 2,540 mm in total length. Catch per unit effort of dwarf sawfish in the late dry season was relatively high in the estuary, with the catch rate in 2015 being one of the highest reported for any sawfish species. Acoustic detections revealed a distinct seasonal pattern in the use of different parts of the estuary and King Sound, which was found to be driven by salinity. Dwarf sawfish predominately occupied a single large pool near the terminus of the tidal limit in the late dry season (August–November), before transitioning to regions in closer proximity to the river mouth or in King Sound in the wet and early dry seasons (December–July). Given the high abundance and residency of dwarf sawfish in the Fitzroy River estuary, this area is an important nursery for the species during the late dry season and should be formally recognized as a habitat protection area for the species.

Original languageEnglish (US)
Pages (from-to)2164-2177
Number of pages14
JournalAquatic Conservation: Marine and Freshwater Ecosystems
Volume31
Issue number8
DOIs
StatePublished - Apr 18 2021
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank the many people that assisted in this research, including Team Sawfish, the Nyikina Mangala Rangers, the Dambimangari Rangers, Yeeda Station, Mitre 10 Derby, Jim and Geraldine Kelly, Brad Norman, Peter Kyne, James Keleher, Brendan Ebner, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), and the people of the West Kimberley. The study was jointly funded by Murdoch University and an Ord River Research Offset grant through CSIRO.

Publisher Copyright:
© 2021 John Wiley & Sons, Ltd.

Keywords

  • behaviour
  • brackish
  • endangered species
  • fish
  • fishing

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