Environmental DNA (eDNA) tools developed at the University of Maine were successfully deployed in four coastal streams in Casco Bay, Maine in spring 2018 to detect the presence of anadromous rainbow smelt (Osmerus mordax), the first full application of this emerging technique. Field methods were refined and tested at sites with documented high (2) and low (2) spawning productivity. Samples were collected below known spawning areas immediately upstream of estuarine tidal influence 2-3 times each week during the spawning season. Three replicate samples were collected in the field at each site, as well as a contamination control, and all samples were filtered and preserved for laboratory analysis. Extracted eDNA samples and controls were run on three replicate qPCR assays.
Initial efforts to extract eDNA from samples were hampered by the presence of environmental inhibitors. Use of a Zymo OneStep PCR Inhibitor Removal Kits appears to have overcome this problem and field collected eDNA samples were amplified successfully using quantitative polymerase chain reaction (qPCR). In partnership with a qualified lab, these tools can now provide a low-cost, userfriendly, and reliable method for monitoring the presence of rainbow smelt
