Quantitative environmental DNA metabarcoding with the qMiSeq approach reflects quantitative capture data of fish community obtained by electrical shocker

Quantitative assessment of biodiversity provides invaluable information for ecosystem conservation and the sustainable use of biological resources. Environmental DNA (eDNA) metabarcoding has been used as a powerful tool for identifying community composition, but it does not necessarily provide quantitative information due to several methodological problems. Thus, quantification of eDNA through metabarcoding is an important frontier of eDNA-based biomonitoring. Particularly, the qMiSeq approach has recently been developed as a quantitative metabarcoding method and has attracted much attention due to its usefulness. The aim here was to evaluate the performance of the qMiSeq approach as a quantitative monitoring tool for fish communities by comparing the quantified eDNA concentrations with the results of fish capture surveys. Water sampling and the capture surveys using the electrical shocker were conducted at a total of 21 sites in four river systems. As a result, significant positive relationships between eDNA concentrations of each species quantified by qMiSeq and both the abundance and biomass of each captured taxon at each site. Furthermore, for 7 out of 11 taxa, a significant positive relationship was observed when the individually quantified DNA concentrations by each sample were pooled and compared with the capture data. In total, our results demonstrated that eDNA metabarcoding with the qMiSeq approach is a suitable and useful tool for quantitative monitoring of fish communities. The simplicity of the eDNA analysis, which only requires the sampling of eDNA from environments, the eDNA metabarcoding with qMiSeq approach would promote further growth of quantitative monitoring of biodiversity.