Gentle identification of fish species through their DNA

Identifying fish species in a river using DNA traces: This method was tested in Switzerland. It proved to be simpler and more reliable than the electrofishing method used to date.

A scientist taking a water sample with a bottle

According to the Swiss National Science Foundation (SNSF), electrofishing, which has been used to date to monitor fish populations, involves anaesthetising the fish with electricity and then collecting them. Electrofishing, which is harmful to fish, is only authorised in Switzerland for scientific purposes.

According to the SNSF, fish populations have therefore only been monitored selectively to date, usually every five years. "Meaningful monitoring of biodiversity is not possible in this way," says study leader Florian Altermatt from the University of Zurich and the aquatic research institute Eawag. In addition, the animals were only identified using this method on the basis of their appearance.

Skin scales and faeces

The environmental DNA method involves searching for traces of DNA in the water. Fish leave these behind via skin scales or faeces, for example. The researchers took two litres of water from dozens of bodies of water and collected the environmental DNA from it. By comparing the genetic sequences with a comprehensive database of fish DNA, the species could be identified.

They compared the results with records from the last 30 years at the respective locations, as well as with electrofishing results. The results matched the historical data on the one hand and, on the other, revealed a greater diversity of species than would have been expected from selective electrofishing.

Written by: sda

Photos: Altermatt lab/Eawag

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