DNA detects fish hot spots: Murray Darling Basin map full of surprises

A DNA map of the Murray-Darling Basin shows which fish species are where - from the pests to perch and cod.

Golden perch DNA was detected in the Lower Darling River, but was absent just above Menindee main weir.

Analysis of 648 water samples collected by citizen scientists at 324 sites across the Murray Darling Basin have picked up the DNA of 144 species, including Atlantic salmon at Red Cliffs on the Murray River.

Unsurprisingly tens of thousands of carp and gold fish sequences were picked up at each site, along with the DNA of mice, dogs and cows.

DNA of a more recent pest species, the oriental waterloach, was also picked up at Echuca.

But more alarming was the absence of some native species, due to basin river barriers.

Golden perch DNA was common downstream of Menindee on the Darling River, but not detected above the town’s main weir, which has no fishway.

As for the detection of Atlantic salmon DNA at Red Cliffs, it remains unclear whether it was from fish at the site or simply the remnants of material washed down from Lake Jindabyne and Khancoban Pondage in NSW, which are stocked with up to 50,000 fry each year.

At the bottom of the Basin, the DNA testing failed to detect any mulloway in the Lower Lakes, which are dominated by carp, but did detect some of the smaller-bodied and rare native fish.

An interactive online map (HERE) allows users to zoom in and click on sample sites, which shows how many times a DNA sequence was counted. (Note: The website has been overloaded with users at times, causing download delays).

The map showing the DNA detected in 648 water samples collected by citizen scientists at 324 sites across the Murray Darling Basin, which identified 144 species.

The frequency of DNA sequences does not indicate how many individuals were detected, but does give a fair indication of the most dominant species at that site.

The DNA sequencing and collation of data was put together by the Murray–Darling Basin Authority and the Odonata Foundation, from samples collected by local citizen scientists in spring last year.

MDBA chief executive Andrew McConville said the eDNA results provide a detailed map of aquatic species distribution across the region that would support policy makers to better protect our most significant ecological communities.

“The findings demonstrate both areas of high biodiversity and unexpected findings, such as the presence of the endangered Purple Spotted Gudgeon in previously unrecorded locations,” Mr McConville said.

“I want to thank the hundreds of citizen scientists who supported the spring sampling whose efforts are helping to inform how we can protect our rivers for generations and the many unique vertebrates that live in the Basin.

“This Great Australian Wildlife Search led by the team from Odonata is made possible with the enthusiasm and energy of Basin communities. Thanks to your participation we have a more comprehensive picture showing the health and biodiversity of our waterways.”

Odonata chief executive Sam Marwood said he was grateful to the MDBA for supporting the early development of the Great Australian Wildlife Search.

“This project represents a revolution in wildlife monitoring, with eDNA sampling allowing for rapid analysis of our waterways,” Mr Marwood said.

“Through regular eDNA sampling we can detect change in biodiversity over time, and inform community, business and government programs that support waterway and environmental health for generations to come.”