Technical report

File type: PDF

Gleiss A, Harry A, Hounslow J, Windstein M, Braccini M, Karajarri R, Travers M (2022). A pilot study into the movement and dispersal of sawfishes. Report to the Reef and Rainforest Research Centre. Cairns, Queensland.



Sawfishes have experienced large reductions in their abundance and extent of occurrence globally, making them one of the most threatened groups of vertebrates. While in some parts of Australia populations are likely comparatively healthy, declines and range contractions have similarly been reported and, as such, their conservation remains a priority. A lack of data on many aspects of sawfish biology is a limiting factor in developing effective, evidence- based conservation strategies. Among the biggest knowledge gaps is the lack of data regarding the distribution and spatial ecology of larger juvenile and adult sawfish once they leave coastal nursery areas. Previous attempts to collect this information using satellite telemetry have had mixed success due to a combination of technological limitations and sawfish biological characteristics.

We revisited the use of satellite telemetry to track the movement and distribution of sawfish and assess the ability of this technology to provide data to address important knowledge gaps regarding their conservation. To do this, we deployed three different models of satellite tag to eight sawfish opportunistically captured during fish surveys in the Kimberley region of Western Australia between October 2021 and May 2022, and tracked their movements for up to 5 months. Except for two tags that failed to provide viable data, all other instruments transmitted high-quality locations daily, demonstrating the potential of satellite telemetry to study sawfishes in Australian waters. Our data revealed that all animals remained resident within shallow subtidal and intertidal habitats and occupied very small activity spaces over the duration of the tracking period. While dwarf sawfish, Pristis clavata, in Prince Frederick Harbour and Lagrange Bay appeared to only associate with mangrove-lined creeks, green sawfish, Pristis zijsron, in Lagrange Bay moved throughout the bay, primarily utilising open intertidal sandflat habitats.

We demonstrate that satellite telemetry can provide important data to address knowledge gaps surrounding sawfishes that will support the identification and abatement of threatening processes and support actions that may lead to the recovery of this taxon. We recommend further deployment of satellite tags in areas where sawfish remain abundant to identify the characteristics of critical habitats for larger sawfish to ultimately construct habitat suitability models able to discern the exposure of sawfish to threatening processes and the amount of habitat protected from such threats.