Comparative Cost and Effort of Fish Distribution Detection via Environmental DNA Analysis and Electrofishing

Fisheries conservation requires accurate knowledge of species identities and distributions. Fisheries are typically assessed via capture-based sampling, but managers frequently are unable to conduct extensive surveys due to budgetary constraints. Sampling of environmental DNA (eDNA) released by fish is a potentially cost-effective approach that could improve species detection per unit effort. However, eDNA methods have not been widely adopted, in part because the cost and effort of eDNA versus traditional sampling are often unclear to managers. We compared the monetary costs and sampling effort required to assess the distribution of Brook Trout Salvelinus fontinalis in a Wisconsin watershed using both electrofishing and eDNA. We detected Brook Trout via both electrofishing and eDNA. The eDNA analysis required lower sampling effort and 67% less cost than triple-pass electrofishing. However, eDNA was more expensive than presence–absence electrofishing, and no population structure information was obtained. Our study illustrates the potential of eDNA to complement traditional sampling methods during fish surveys.