Monitoring fish DNA with a bottle of water

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A one litre water sample is all researchers need to be able to detect the presence of invasive pest fish in our river systems, resulting in improved and tailored management outcomes for local catchment authorities.

Known as environmental DNA monitoring (eDNA for short), it is a specialised technique which can detect small amounts of DNA that fish release into their environment, such as skin cells or faeces, avoiding the need to physically capture fish.

Jonas Bylemans, PhD candidate based at the University of Canberra’s Institute for Applied Ecology who is funded through the Invasive Animals CRC recently published findings in the Journal Biological Invasions comparing the use of the new eDNA monitoring technique against conventional monitoring such as trapping.

The study specifically aimed to determine the spread of the invasive redfin perch in a river system of the Upper Lachlan River catchment in NSW.

“The benefit of eDNA technology is that it 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. 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,” said Mr Bylemans.

Luke Pearce, Fisheries Manager from the NSW Department of Primary Industries manages the Lachlan River catchment and was also involved in the study, saying “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.”

“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,” said Mr Pearce.

The research team at the University of Canberra’s Institute for Applied Ecology are using environmental DNA based monitoring to determine the presence and spread of multiple pest fish species, such as the redfin perch, carp and oriental weatherloach. However, 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. 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,” said Mr Bylemans.

While eDNA monitoring is extremely promising and it can now be used to support management actions, Mr Bylemans highlighted that strict protocols need to be followed and the technique is still being refined.

Mr Bylemans study can be found in the latest edition of Biological Invasions.

Feature image: Jonas Bylemans collecting water samples for his redfin perch eDNA monitoring – taken at Blakney Creek, NSW