The riverscape on a chip: high-throughput qPCR enables basin-wide fishery assessments

To achieve reliable detection of environmental DNA (eDNA) from multiple species, a method which combines the specificity of single-taxon assays with the broad taxonomic coverage of metabarcoding is needed. High-throughput quantitative PCR (HT-qPCR) has emerged as one such method that holds particular promise for ecological applications. Here, we present the development and validation of a HT-qPCR biochip (i.e., biochip) protocol for a suite of western North American fishes with high cultural, economic, and ecological significance. Coupling this biochip with systematically distributed eDNA samples collected by citizen scientists, we evaluated the distribution of multiple species throughout a large river basin in the U.S. Pacific Northwest. Patterns of detection using the biochip were comparable to those using single-taxon qPCR (ST-qPCR; mean concordance = 0.917), despite the biochip using 90% less DNA per taxon and reducing costs by an estimated 40%. Comparisons between biochip results and distributions derived from conventional methods demonstrate that this approach not only offers more reliable and high-resolution distribution data for these species but also achieves this more efficiently than traditional sampling methods.