Evidence for Particle Dilution and Dispersion as the Strongest Effects on Reach-Scale Salmonid eDNA Sampling Outcomes in Mediterranean-Climate Rivers and Streams
Environmental DNA (eDNA) sampling from rivers has emerged as a promising new method for monitoring freshwater organisms of management concern. However, to more confidently interpret eDNA sampling results – and thereby improve eDNA as a tool for management decision making – the influence of local environmental factors on eDNA fate (transport & decay dynamics) must be better understood. At nine river sites across the central California coast, we added a known quantity of novel eDNA (Brook Trout, Salvelinus fontinalis) and collected eDNA at sequential downstream distances for qPCR analysis. We then used random forest modeling to identify the most important factors to reach-scale sampling outcomes and characterize salmonid eDNA fate. Our results offer evidence of particle dilution and dispersion as primary drivers of salmonid eDNA sampling outcomes at the reach scale. In addition, we highlight the interplay between discharge, velocity, and cross-sectional area as key to interpreting eDNA data for future management goals
