Using eDNA to improve environmental monitoring for water bodies effected by hydropower in Sweden

Abstract: The aim of this report is to contribute to the base of knowledge on environmental monitoring by increasing understanding of how eDNA, electrofishing and sampling fishing may be used to examine fish biodiversity. It also aims at understanding if fish indexes developed within the Water Framework Directive reflect biodiversity, as well as the potential of eDNA data to serve as input to these indexes. This was done by using three different approaches. Firstly, in order to establish which of the methods eDNA, electrofishing and sampling fishing is more suitable to measure the different dimensions of biodiversity (species richness, species evenness and genetic diversity), a literature review comparing the different methods was carried out. It was found that eDNA yields a more detailed results for species richness, electrofishing yields better results for species evenness and sampling fishing is outperformed by eDNA and electrofishing alike. Both electrofishing and sampling fishing may collect data for genetic diversity analysis, however electrofishing outperforms sampling fishing with regards to amount of species caught, making electrofishing a more suitable data collection method. Secondly, in order to gain insight on practical usage of eDNA, a case study of Spjutmo (Dalarna county) was reviewed. It was established that eDNA generated more detailed information of species richness in the case of Spjutmo (as compared to electrofishing). The relative abundance data generated by the eDNA study might be seen as a measure of species evenness. However, electrofishing yielded data which may serve as input to species evenness indices. To the best knowledge of the author, none of the methods generated data on genetic diversity in this specific case. Officials from the energy company Fortum and the county board of Dalarna were also interviewed in order to get insight on what potential they see for eDNA to contribute to environmental monitoring. Both officials point at the ability to estimate abundance as a desired feature, hence a better understanding of what the relative abundance results indicates is wanted. The two interviews indicate that this understanding is an important feature to develop in order to make metabarcoding studies effective in current environmental monitoring. Thirdly, in order to understand if fish indexes developed within the Water Framework Directive reflect biodiversity, a literature review was performed. It was found that, all but one of the compared indexes incorporates or somewhat incorporates species richness. However, only five indexes are indicative or somewhat indicative of species richness. Species evenness is incorporated or somewhat incorporated by two indexes, which are also indicative or somewhat indicative of species evenness. None of the indexes incorporate or indicate genetic diversity. Within the third literature review, the potential of eDNA data to serve as input to current fish-based indexes developed within the Water Framework Directive, was studied. It was found that eDNA data may serve as input to only one index in its present form. However, five indexes also use proportional information (e.g. proportion of tolerant species), which possibly could be provided by eDNA data. The index where usage of eDNA data is currently possible uses presence-absence information.