Animals in aquatic environments—such as fish, amphibians, crayfish, and mussels—release DNA into the water via their feces, urine, and skin. This external DNA is called environmental DNA (eDNA). By filtering water samples and analyzing them for eDNA, one can determine whether a species is present without actually capturing or seeing an individual. Different species can be identified by using genetic markers that are unique to them.
Because of its greater efficiency and reduced cost, eDNA sampling may revolutionize the monitoring and assessment of freshwater species.
Researchers at the U.S. Forest Service’s National Genomics Center for Wildlife and Fish Conservation (NGC) have pioneered developments in this field—including the first reliable eDNA assay for salmonid fish species. NGC scientists developed a rapid, field-proven eDNA sampling protocol that is remarkably sensitive—100% detection efficiency of target species has been attained across order-of-magnitude changes in stream discharge, and detection rates of rare species can be much higher than with traditional sampling methods. Moreover, collected samples are easily stored in the field, can be processed in the lab in under 48 hours, and cost relatively little to analyze. Assays are available or being developed for an array of native and nonnative species.
NGC scientists introduced biologists from partner agencies across the West to this approach by providing training and lending equipment from our “tool library.” Successful projects have included finding new populations of sensitive species, delineating the boundaries of habitats occupied by fish, and gauging the effectiveness of efforts to remove nonnative species.