Environmental DNA (eDNA) detection and habitat occupancy of threatened spotted gar (Lepisosteus oculatus)

Determining the occurrence and site occupancy of rare and endangered species can be challenging, particularly without causing harm or stress to the species of concern. Environmental DNA (eDNA) detection was used to assess habitat occupancy by spotted gar (Lepisosteus oculatus), which is federally listed as Threatened in Canada, with known occurrences limited to a small number of locations in southern Ontario. Quantitative polymerase chain reaction (qPCR) assays were developed to detect spotted gar eDNA, which was detected in all but one previously recorded location. The eDNA method was shown to be more effective than traditional netting for detecting spotted gar habitat use. The use of qPCR allowed for quantification of substantial variation in detection strength (copy number) among replicate eDNA samples, with implications for establishing sampling designs for detection and surveillance. The use of eDNA for detection and monitoring of aquatic species of conservation concern shows great potential as a non‐invasive method for assessing species occurrences and habitat occupancy, as well as for informing targeted sampling by conventional capture methods.