Midwest Fish & Wildlife Conference 2019

AUTHORS: Emy Monroe, Erica Mize – U.S. Fish and Wildlife Service; Richard Erickson, Christopher Merkes – US Geological Survey; Nicholas Berndt, Katherine Bockrath, Jeena Credico, Nikolas Grueneis, Jenna Merry, Kyle Mosel, Maren Tuttle-Lau, Kyle Von Ruden, Zebadiah Woiak, Kelly Baerwaldt, Sam Finney – U.S. Fish and Wildlife Service; Jon Amberg, US Geological Survey

ABSTRACT: Natural resource managers use data from survey or monitoring efforts that use a wide variety of tools. Environmental DNA (eDNA) is a genetic surveillance tool for detecting species and holds potential as a tool for large-scale monitoring programs.  Two challenges of eDNA-based studies are imperfect capture of eDNA in collection samples (e.g., water field samples) and imperfect detection of eDNA using molecular methods (e.g., quantitative PCR), which create uncertainty about sample designs for eDNA-based monitoring.  We used an occurrence model to address these challenges and determine how many  samples were required to detect species using eDNA and to examine when and where to take samples.  Water samples were collected from three different habitat types in the Upper Mississippi River when both Bighead Carp and Silver Carp were known to be present based on telemetry detections.  Each habitat type was sampled during April, May and November.  Detections of eDNA for both species varied across sites and months, but were generally low, 0 - 19.3% of samples were positive for eDNA.  Additionally, we found statistical artifacts where sample eDNA capture probabilities would artificially inflate estimates of molecular detection probabilities.  Overall, we found that eDNA-based sampling holds promise to be a powerful monitoring tool for resource managers, however, limitations of eDNA-based sampling include different biological and ecological characteristics of target species as well as aspects of different physical environments that impact the implementation of these methods.