Tracking Ghosts: Using Environmental DNA Detection to Find Invasive and Endangered Aquatic Species in Ontario

Effective management of both endangered and invasive species requires sensitive detection of species occurences, often at low abundances.  In aquatic environments, detection of rare species such as endangered taxa or early-stage invasive species can be further confounded by site accessibility, sampling gear, and capture efficiency, with direct observation being difficult at best. Discriminating between detection failure (null) versus true absence (zero) can be problematic, but has significant consequences for species and habitat management.  Experimental trials using environmental DNA (eDNA) in a controlled environment to determine species occurrence confirmed the taxonomic specificity and spatial, temporal, and quantitative sensitivity of eDNA detection.  As a result, eDNA surveillance is currently being used in Ontario, using both regular and quantitative PCR of "barcoding" mtDNA regions to track the presence or absence of aquatic Species At Risk (spotted gar and redside dace) in natural habitats, as well as to survey Ontario waters of Lake Erie for the potential occurrence of Asian carps (bighead and silver carp).  The combined results indicate that environmental DNA is a reliable method for species detection in freshwater systems, and can be used as an effective sampling technique for detecting both invasive and endangered freshwater species.