Efficacy of Environmental DNA to Detect and Quantify Brook Trout Salvelinus Fontinalis, Populations in Streams of the Adirondack Mountains, New York

Environmental DNA (eDNA) analysis is rapidly evolving as a tool for monitoring the distributions of aquatic species. Detection of species populations in streams is problematic because the persistence time for intact DNA fragments is unknown, and eDNA is diluted and dispersed by dynamic hydrological processes. During 2015, Brook Trout Salvelinus fontinalis, eDNA was analyzed from waters collected at 40 streams across the Adirondack Mountains where their populations were recently quantified to evaluate sampling methods and the ability of Brook Trout eDNA to accurately predict the presence and abundance of local populations. Results from 3-pass electrofishing surveys indicate that Brook Trout were absent from 10 sites, and present in low (<100 fish/0.1 ha), moderate (100-300 fish/0.1 ha), and high (>300 fish/0.1 ha) densities at 9, 11, and 10 sites, respectively. Environmental DNA results correctly inferred the presence-or-absence of Brook Trout populations in 92.5% of the study sites and explained 44% of the variability in density and 24% of the variability in biomass of local Brook Trout populations. These findings indicate that eDNA is an effective tool for characterizing the presence or absence, and the abundance of Brook Trout populations in headwater streams across the Adirondack region and elsewhere.