NL-Fish Population Scan determines species composition of fish populations

The presence or absence of fish species provides information about the quality of the water. Within the ‘Monitoring fish migration through eDNA’ project of the TKI Water Technology programme, a new method has been developed to monitor the species composition of a fish population. The NL-Fish Population Scan does this using a new, publicly-available eDNA metabarcoding analysis. The scan can demonstrate the presence of a great diversity of fish species. The NL-Fish Population Scan is potentially a good alternative to current sampling methods in determining species composition. The project was conducted by KWR in collaboration with ATKB, BaseClear, the Aa and Maas, Brabantse Delta and Limburg Water Authorities, and Witteveen+Bos.

Monitoring fish populations

To bring the ecological quality of European waters up to standard, water management entities have to implement extensive sets of measures. In this way they can satisfy the requirements laid out in the Habitats Directive and particularly those in the European Water Framework Directive (WFD).

To determine which fish are present, the fish are captured and returned to the water following examination. The current sampling methods have their limitations when it comes to rare and hard-to-capture species. They are also time-consuming, labour-intensive and thus costly, and moreover disturb the fish and their habitat. There is a need for a reliable, cost-effective and non-disturbing method to monitor the distribution and migration of fish populations.

NL-Fish Population Scan

New methods that focus on the presence of eDNA are an animal-friendlier, more easily standardised, possibly also more reliable and, over time, cheaper way of determining which fish species are present. To monitor the species composition of a fish population, this project developed a new, publicly-available eDNA metabarcoding analysis: NL-Fish Population Scan. The method identifies traces of DNA which the fish shed into the environment. These traces come for instance from faeces, slime, skin or scales. With the metabarcoding analysis one can determine, on the basis of species-specific DNA codes, which fish species are involved. The method has been validated in the lab and tested in practice.

The research results show that the use of the NL-Fish Population Scan in the waters in which sufficient eDNA could be collected demonstrated the presence of a great diversity of fish species. Moreover, the use of a special eDNA analysis, focused on a few target species, produced a picture of the quantitative distribution of the eDNA of these populations. A thorough interpretation of the data will however require further investigation.

The eDNA extraction method employed in the field was not able to acquire sufficient eDNA for all of the samples studied. For the time being, reliability would be served if the eDNA from the water samples were filtered in the lab.

See the report on the Monitoring fish migration through eDNA project page. The method is discussed in more detail in Water Matters (nr 2, 2017). A comparison with the results of simultaneous, conventional fish monitoring methods in various waters will also soon be published in Water Matters.