Influence of distance from source population and seasonality in <scp>eDNA</scp> detection of white‐clawed crayfish, through <scp>qPCR</scp> and <scp>ddPCR</scp> assays

The white-clawed crayfish (Austropotamobius pallipes) is an emblematic taxon of European rivers, found mainly in oxygenated streams, known to be excellent indicator river quality. Since several decades, the population A. pallipes declined relation anthropogenic pressure, habitat loss, and competition with pests (invasive crayfish, plague). This endangered species now submitted conservation strategies by freshwater managers order survey protect remaining populations. In France, traditional surveys environments were performed electric fishing, kick-net or trapping, particularly disruptive for environment very time-consuming. However, rise molecular genetic technology, new methods based on detection environmental DNA (eDNA) have emerged. We present here results optimized study Austropotamobius considering certain co-factors comparing two PCR (qPCR ddPCR). After improving laboratory procedures, we able detect presence up 2 km downstream from a point unfortunately highlight disappearance historical population, after sampling consecutive years. Such level precision interesting because it makes possible precise specimens relatively restricted area orient prospecting, necessary additional studies. During our study, observed better probabilities during summer period, but growing context climate change, advise adapt year year. That said, this methodology useful tool rare and/or endemic did not observe any difference between used.