Aussie scientists have developed a cutting-edge test that could give the ugly but endangered largetooth sawfish a better chance of survival.

They’ve found a way to reliably test large bodies of water for the DNA of the prehistoric-looking fish, and that will make key habitats easier to identify.

Until now researchers have had to rely on costly fish surveys and the knowledge of locals to understand where the critically endangered species lives, but the new test promises to change that.

Professor Colin Simpfendorfer, from James Cook University, says the technique has proven to be accurate at remote water holes in the Northern Territory.

Australian scientists have developed a cutting-edge test that could give the critically endangered largetooth sawfish a better chance of survival. Photo: AAP/James Cook University

It’s less effective in flowing rivers, but he expects that will be overcome as the technology is refined.

“This is very much a trial phase and it will be solved quite easily given some more time,” he says.

The test is no small development for the species, which may already be extinct in 50 countries. Northern Australia is one of the last places where it can still reliably be found.

“We don’t even know if they still exist in many countries. Applying this approach globally will enable us to rapidly find threatened populations and prioritise their protection.”

The testing technique is known as eDNA, or environmental DNA.

Prof Simpfendorfer says its applications are not limited to fresh water or conservation applications.

“There is a big push to roll it out globally. It has many other potential uses, such as detecting invasive pest species at ports.”

-AAP