Environmental DNA (eDNA) detects the invasive rusty crayfish (Orconectes rusticus) at low abundances

Early detection is invaluable for the cost-effective control and eradication of invasive species, yet many traditional sampling techniques are ineffective at the low population abundances found at the onset of the invasion process. Environmental DNA (eDNA) is a promising and sensitive tool for early detection of some invasive species, but its efficacy has not yet been evaluated for many taxonomic groups and habitat types. We evaluated the ability of eDNA to detect the invasive rusty crayfish Orconectes rusticus, and to reflect patterns of its relative abundance, in upper Midwest, USA inland lakes. We paired conventional baited trapping as a measure of crayfish relative abundance with water samples for eDNA, which were analysed in the laboratory with a qPCR assay. We modelled detection probability for O. rusticus eDNA using relative abundance and site characteristics as covariates, and also tested the relationship between eDNA copy number and O. rusticus relative abundance. We detected O...