Development and Application of an eDNA Assay to Delineate the Distribution of the Imperiled Striated Darter (Etheostoma striatulum, Page and Braasch 1977) in the Duck River, Tennessee
Effective conservation of rare or imperiled species relies on efficient monitoring and accurate information regarding distribution, critical habitat locations, and occupancy. However, most imperiled species are inherently cryptic and difficult to capture due to patchy distributions and low population densities. To avoid these obstacles, environmental DNA (eDNA) detection techniques have been developed to provide a more sensitive and economical solution for species monitoring. Striated Darters are small, uncommon darters endemic to the middle-to-upper regions of the Duck River, Tennessee. Since their description in 1977, they have become increasingly rare throughout their range; as of 2011, their distribution had declined to nine of the 16 historically occupied tributaries. Due to this documented decline, Striated Darters are currently in review for federal listing under the Endangered Species Act and are currently listed as state threatened in Tennessee. Because of their reclusive and cryptic behavior, conventional techniques tend to be less effective for detection, requiring more sensitive methods. Our study aimed to develop an eDNA surveillance assay and protocol to detect presence of the Striated Darter at 30 historical sampling sites and to delineate their current distribution. Data were analyzed using a hierarchical occupancy model approach to estimate occurrence and detection probability at the scales of sites, sample replicates, and qPCR reaction replicates.