Within the last 15 years, the fish ecological status of hundreds of water bodies in Austria has been assessed with the Austrian Fisch Index (FIA). This assessment, according to the European Water Framework Directive (WFD), has far-reaching implications for the further implementation of this directive in Austria. Since measures to improve the ecological status/potential of water bodies, such as river restoration, are very cost-intensive, it is of great importance to have a data basis for the classification of water bodies as complete and solid as possible. Electrofishing is the main fishing method to obtain data for the FIA. Due to the limited effect of the electric field, the significance of electrofishing decreases in deeper and larger water bodies. Supplementary fishing methods, such as electrified bottom trawls, drift gillnets, longlines, multi-mesh nets and hydroacoustic surveys, are also personnel- and cost-intensive, sometimes harm the fish caught and cannot eliminate completely the existing data deficits in the documentation of the fish population.
The use of eDNA, i.e. the analysis of fish DNA from water samples, as a complementary, non-invasive method to electrofishing seems to make sense, since sampling is very fast and inexpensive with little manpower required, has a higher detection probability for rare, often endangered fish species, and their analysis methods are constantly being refined and developed. Furthermore, in addition to improved species detection, it is highly likely that this method can provide robust data on fish density and fish biomass, two essential parameters within FIA assessment, using quantitative eDNA (qPCR) analysis. The aim of this project is to investigate eDNA as a potential additional method for the assessment of fish ecological status according to the EU WFD in Austria and to demonstrate both its potential and limitations. For this purpose, comparative sampling, i.e. simultaneous traditional electrofishing and eDNA sampling, will be performed at selected streams in Austria. With these investigations, the potential of this new method for fish population surveys will be evaluated, in order to be used subsequently as an additional method in the assessment of the fish ecological status in Austria. |