Investigating Aquatic Species Distributions for Sequoia and Kings Canyon National Parks: A Comparison of Visual and Environmental DNA Surveys in Streams

Biodiversity monitoring is a difficult and expensive activity that is chronically underfunded. Visual Encounter Surveys (VES) are a common monitoring tool for poikilothermic organisms in streams and rivers, but many species are challenging to detect with this method. Environmental DNA (eDNA) detection methods have been growing in popularity as a supplement or replacement for VES for aquatic species, but they are not yet widely adopted, in part due to perceived costs, a lack of understanding about their efficacy, and a lack of technical expertise. We implemented a paired VES and eDNA survey of 13 species (6 native and 7 invasive) in three rivers within and around Sequoia and Kings Canyon National Parks (SEKI). We found that species detection using eDNA methods was consistently higher compared to traditional snorkel VES, and eDNA was an accurate, cost-effective method for detecting biodiversity. Using eDNA and VES techniques, we were able to conduct a survey of aquatic biodiversity in areas within and neighboring the SEKI boundary. Our work highlights the potential for eDNA methods to be used in conjunction with traditional VES to minimize costs and improve capacity for resource management.