Sawfishes (Family Pristidae) are the most threatened family of elasmobranch (sharks and rays), with all 5 species listed on the IUCN Red List of Threatened Species as either Critically Endangered or Endangered. Limited observational data and expert opinion suggest that sawfish species are now extinct in at least 20 countries within their former distribution, and are possibly extinct in many more.
A lack of understanding the remaining extant range of sawfish due to their rarity and scattered occurence in remote regions has hampered our ability to implement recovery strategies. Researchers from James Cook University and Charles Darwin University have tested the utility of DNA barcodes obtained from environmental DNA (eDNA) to find the freshwater largetooth sawfish (Pristis microdon) in remote northern Australia.
Before trying the technique in the wild some initial tests were done on water samples from different aquaria and the colleagues were able to correctly tell which contained largetooth sawfish. Traditional methods to search for sawfish, such as fishing surveys, can be expensive and time-consuming. To test the approach in the wild, the research team sampled known largetooth sawfish habitats in the Daly River, Northern Territory. They partnered with indigenous owners and rangers.
The method was mostly accurate in waterholes but not as good in flowing rivers likely the result of the high water flow and the associated turnover rates . This is not a big problem, this is very much a trial phase and it will be solved quite easily given some more time. Within five to ten years it's hoped that all eDNA analysis will be able to be completed in the field, with no need to take samples back to the lab.