The new trend in aquatic research is to use environmental DNA (eDNA) as a method to detect fish species from water samples, without seeing or catching a single individual. This is made possible by tracing the DNA that species release into the environment. The popular game fish Northern pike (Esox lucius) is hard to monitor with the standard survey, multi-mesh gillnets, there are difficulties to reliably estimate density and to accurately provide data for reliable status assessments. Quantitative eDNA could be a useful complementary tool if it can provide reliable estimates of pike density. This project tried to investigate the possibility to detect differences in Northern pike density, using eDNA as a quantitative method, with three different extraction kits and two different filter types. The results revealed that it was possible to separate different pike densities, regardless of filter combination and extraction kits. The experiment also revealed that adding a GF/A filter to a CN filter did not yield more compared to what a single CN filter retrieved. This facilitates future studies due to faster filtration when using one filter and not two. Moreover, the experiment showed that Chelex as an extraction method yielded the most eDNA compared to the other two kits: Blood and Tissue and PowerWater. Although there are several questions to address before eDNA can practically be used for monitoring pike.
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