Australia is one of the last strongholds for sawfish in the world as populations elsewhere have declined or become extinct. To ensure Australian sawfish populations stay healthy, northern Australia fishers and research organisations are collaborating to understand the impact of sawfish bycatch.
By Dempsey Ward
A lack of data on sawfish population size, combined with historically inadequate reporting in Australian commercial fisheries, makes it impossible to determine the impact of sawfish bycatch on their regional population numbers, according to lead researcher Dr Richard Pillans of CSIRO. While reporting in some fisheries has improved in the last few years, there is still not enough data to determine the cumulative impact of bycatch in all the fisheries that interact with sawfish.
“The concern right now in Australia is trying to figure out how many sawfish are left. We know from talking to fishers that they used to be a lot more abundant, but there has been no scientific data on the extent of their declines, or current abundance”, says Richard.
The project will gather tissue samples and deploy satellite tags on all four Australian Sawfish Species: Largetooth Sawfish (Pristis pristis), Green Sawfish (Pristis zijsron), Dwarf Sawfish (Pristis clavata) and Narrow Sawfish (Anoxypristis cuspidata).
Tissue samples will assess Sawfish population size and stock structure using Close-Kin Mark-Recapture, a scientific method that uses genetic relatedness of sampled sawfish to estimate abundance. Satellite tags will allow determination of the post-release survival rates of sawfish captured as bycatch by trawling and gillnets.
Pictured: Sawfish being satellite tagged
The project is working with several fisheries across the north to help the study succeed, including the Northern Prawn Fishery, the NT Barramundi Fishery and Queensland’s Gulf of Carpentaria inshore and offshore gillnet fisheries.
“Without data on sawfish abundance and rates of interactions with commercial fisheries, scientifically rigorous management of this iconic species is impossible. This is why working with commercial fisheries is vital to the success of the project - twenty or thirty data points isn’t enough, we need hundreds.”
Richard says the project will engage and collaborate with the commercial fishing industry in northern Australia at a level not previously conducted.
This includes engaging with industry champions to build trust between researchers and the gillnet and trawling industry in Northern Australia.
“So many people [in the industry] have great practices, so we, the researchers are trying to learn from them; how do they release sawfish alive without getting themselves hurt?” Richard asks.
Pictured: Sawfish being released by a gillnet fisher in the Gulf of Carpentaria Barramundi Fishery. Photo credit: Richard Pillans CSIRO
“The team is also looking to work with industry champions to get them to try and bring everyone else along and elevate the message that reporting interactions with sawfish and other protected species will result in better outcomes [for the industry], than if there was no reporting.”
No time to waste
Richard and his project team have already begun work with the Northern Prawn Fishery, located off Australia’s northern coast, from Cape York in Queensland to Cape Londonderry in Western Australia.
They have handed-out tissue sampling kits and trained the Northern Prawn Fishery crew member observers (there are ten in the fleet) how to use them, and Australian Fisheries Management Authority observers how to deploy satellite tags.
Gillnet fisher Shane Batch (left) was a recipient of a sampling kit by Richard Pillans (right) and his team.
“The NPF is proactively and enthusiastically engaged in trying to address the issue. We have seen high uptake and participation so far.”
“With sufficient sawfish tissue samples collected by commercial fishers across northern Australia, this project will enable management decisions to be informed by robust data.”
The project is on track to finish midway through 2026.
This initiative is a partnership between the commercial fishing industry, CSIRO and Charles Darwin University. This project is jointly funded by FRDC and the Australian Government under the National Environmental Science Program.
2022-068: Multi-fishery collaboration to assess population abundances and post release survival of threatened Sawfish captured in commercial fishing operations in Northern Australia