What was this project about?
Living Water wanted to determine if there are less invasive methods of detecting whether pest fish species were in the Peat Lakes. Traditionally, monitoring of pest fish species has required intensive trapping or electric fishing to detect incursions or identify the spread of species.
A new approach to detecting species using environmental DNA (eDNA) has been developing over the past 30 years. All organisms leave traces of DNA in their environment, through shedding cells such as hair, scales, skin and faeces. Consequently a sample of water, soil or sediment can be used to detect species present. Genetic material is extracted from the sample using PCR (polymerase chain reaction). It is a technique used to amplify a segment of DNA of interest to produce lots of copies, and DNA sequences are matched against a database of known sequences for species.
How was the project undertaken?
Living Water used eDNA testing to identify whether Koi carp (Cyprinus carpio) were present at Lake Ruatuna alongside conventional pest fish surveys run in 2015, 2018 and 2019.
What has the project achieved?
Two of six initial samples collected in 2018 indicated the presence of Koi carp. However, further intensive eDNA sampling in early and late 2019 and repeat pest fish netting suggested no Koi were present. The initial positive indication could mean Koi were present in low abundance or at locations not targeted in further sampling, or contamination, false positives or false negatives.
Living Water’s eDNA investigations at Lake Ruatuna have contributed to further DOC work into the use of eDNA to detect species.