Analysis of sea lamprey environmental DNA during lampricide treatment in a tributary of Lake Ontario

Sea lamprey (Petromyzon marinus) is a species of invasive parasitic fish in the Great Lakes region of North America. Accurate estimates of larval lamprey populations in lake tributaries are necessary for making control decisions regarding treatment of lake tributaries with 3-trifluoromethyl-4-nitrophenol (TFM), a piscicide toxic to lamprey larvae. Analysis of environmental DNA (eDNA) isolated from water samples is a recent innovation under consideration for sea lamprey biomonitoring. eDNA analysis was performed before and at three time points after TFM treatment in a tributary of Lake Ontario (Ninemile Creek) to assess presence of invasive sea lamprey. Lamprey DNA was detected in four out of four sample locations before TFM treatment and three of four locations 72 hours following treatment. No lamprey DNA was detected in any of the locations 4 months or 12 months after TFM treatment of the creek. These results are consistent with known effectiveness of TFM treatment and provide evidence for the potential of eDNA analysis as a tool for monitoring decline of larval sea lamprey abundance due to TFM treatments.