Helping Crater Lake's Slovenian Sister Park Find Invasive Fish With eDNA

By David Hering, aquatic ecologist, Crater Lake National Park. From the "Picture This" section of Park Science magazine, Volume 36, Number 1, Summer 2022.

Collecting and filtering water for eDNA analysis at Lake Krn in Triglav National Park, Slovenia. Lake Krn and the other lakes sampled had no fish naturally until exotic minnows and char were introduced, which now threaten some alpine lakes' ecology. NPS/David Hering.

In 2019 I travelled to Triglav National Park, Crater Lake's sister park in Slovenia, a small, beautiful central European country rich in forests, lakes and rivers. I went to help park biologists sample environmental DNA (eDNA) from lakes high in the Julian Alps, looking for traces of non-native minnows and Arctic char that disrupt the park's lake ecosystems.

Sharing a technique

The work demonstrated eDNA methods used in the United States and gave baseline data on fish DNA in Slovenian lakes, and both parks are trying to undo the damage invasive fish do. Triglav's fish biologists knew of eDNA but had never used it. Our collaboration showed its value and encouraged Slovenia's fisheries agency to develop its own eDNA protocols, and after my visit Triglav began removing non-native fish from Dvojno Jezero ("Double Lake").

Slovenian colleagues Miha Ivanc (front), of the Fisheries Research Institute of Slovenia, and Boštjan Podgornik, of Triglav National Park. NPS/David Hering.

Why eDNA

eDNA analysis is transforming how we find where organisms live, especially rare or hard-to-catch species. It can be more sensitive than netting or electrofishing, which suits it to spotting invasive species early and to checking whether eradication has worked.

I filtered water from several lakes, including Dvojno Jezero. Back in the United States, colleagues at the U.S. Forest Service used quantitative polymerase chain reaction (qPCR) to measure how much non-native fish DNA each liter of water held. With a Fulbright Specialist grant, I planned to return to repeat the measurements and record the drop in non-native DNA after the fish are removed.

Jezero v Ledvicah ("Lake at Ledvicah") in Triglav National Park, which, as far as I could tell, has no non-native fish yet. NPS/David Hering.

Sources

• David Hering, "I Helped a Slovenian Park Find Elusive Alien Fish," Park Science 36(1), Summer 2022, National Park Service. https://www.nps.gov/articles/000/i-helped-a-slovenian-park-find-elusive-alien-fish.htm
• The author's portrait is not reproduced here.