Field application of an eDNA assay for the threatened white-clawed crayfish Austropotamobius pallipes

The white-clawed crayfish Austropotamobius pallipes has experienced extensive population declines in its native range in the last century and is now a threatened species. European legislation, therefore, requires A. pallipes populations to be monitored regularly and that Special Areas of Conservation (SACs) be designated in part of their range. These needs cannot be met without knowledge about the distribution of this species. However, common crayfish sampling approaches can be time consuming, expensive, or yield false negatives at low population densities. We, therefore, present an environmental DNA (eDNA) assay based on the mitochondrial cytochrome oxidase I (COI) gene to detect A. pallipes in water samples with species-specific primers, a minor groove binding (MGB) probe, and quantitative PCR. The results reflected the expected distribution of A. pallipes based on the known locations of this species in the catchment areas sampled. The results of this study indicate that eDNA is an effective tool for detecting A. pallipes in a lotic system and could, therefore, provide a valuable, non-invasive method for determining its distribution.