Environmental DNA as an effective tool for detection of imperiled fishes

Detection of aquatic species is imperfect, especially if the species is rare and exhibits spatial and temporal variability. Many fish species require a number of sampling trips before detection is positive. And yet, information on species persistence is critical for effective conservation efforts. New forensic genetic techniques, such as environmental DNA (eDNA), have been developed and successfully used to validate the presence of exotic aquatic species in new areas. We compared detection of a federally listed, threatened, migratory fish species the Slackwater darter (Etheostoma boschungi); using eDNA to concomitantly collected field collections. Detection probabilities for this species are variable, but consistently low in recent collections. Our results indicated that detection using eDNA was vastly more effective than traditional sampling at confirming the presence of the Slackwater darter. Positive detection at non-breeding sites was half of the detection rate at breeding sites, most likely to the greater area available in non-breeding streams. These data suggest that eDNA is an effective tool for quickly evaluating a relatively large number of sites for the presence of rare aquatic species.