The identification of the species, known as Gammarus fossarum, was verified by its morphology and by barcoding its DNA.
“The original purpose of the sampling was to carry out a comparison of traditional sampling and eDNA/DNA methods,” said lead author Rosetta Blackman.
The species was found in several rivers in England and Wales, including the Frome, Ribble and Taff.
Widespread in Europe, the shrimp is very similar in morphology to G.pulex, which can be found in the UK and mainland Europe.
The two species typically inhabit different parts of freshwater rivers – G.fossarum is found in the upper reaches of mountainous streams and G.pulex in lower river sections – but they can coexist.
Following the discovery of G.fossarum, the scientists examined historic material from the Natural History Museum using microscopes, and found G.fossarum had been found as far back as 1964 but was misidentified as a different species.
“The features which separate the two are very small and as G.fossarum does not appear in the British freshwater identification guides, it is likely that it has been missed as analysts didn’t know what to look for,” said Blackman.
The Chartered Institute of Ecology and Environmental Management said: “This study is one of the first to demonstrate the potential of eDNA metabarcoding for passive detection of non-native species.”
The use of eDNA in surveying has been used for detecting species such as the great crested newt.
Read the full paper in Aquatic Invasions
Main image: Gammarus fossarum has been discovered in the UK using eDNA. © Drew Constable