Environmental DNA monitoring to detect river pests

Researchers from the University of Canberra have discovered that environmental DNA (eDNA) monitoring, a specialised technique that can detect DNA that fish release into their environment through skin cells or faeces, is even more effective than conventional monitoring techniques such as trapping.

Published in the journal Biological Invasions, the study saw the researchers determine the spread of the invasive redfin perch in a river system of the Upper Lachlan River catchment in NSW. As noted by Luke Pearce, fisheries manager from the NSW Department of Primary Industries, “Redfin perch are a major threat to the Lachlan River catchment; they predate on vulnerable native fish such as the southern pygmy perch and compete with native fish for resources — they need to be contained and controlled.”

PhD candidate Jonas Bylemans, corresponding author on the study, said eDNA technology is “a highly sensitive technique, able to detect small amounts of DNA in a water sample”.

“Our study showed that eDNA monitoring was able to detect the presence of redfin perch in locations where the conventional monitoring was not,” he said. “This shows that the eDNA monitoring is able to detect species at low densities, whereas conventional monitoring is only really efficient for species with reasonably high densities.”

The research team at the University of Canberra’s Institute for Applied Ecology are using eDNA monitoring to determine the presence and spread of multiple pest fish species, such as the redfin perch, carp and oriental weatherloach. The technology can also be used to determine the presence of threatened native fish species.

“The added benefit of the eDNA monitoring technique is that we are able to detect multiple species,” said Bylemans. “We know that redfin perch can threaten native fish and so we are also interested in understanding the impact this pest fish might be having on the entire native fish community.”

eDNA monitoring can now be used to support management actions. According to Pearce, “The use of the eDNA monitoring gave us an ability to target containment measures in the catchment to ensure the spread of the pest fish is minimised.”

Bylemans noted that strict protocols need to be followed and the technique is still being refined.