Environmental DNA survey dataset for fish and amphibians in mountain lakes of Olympic National Park

In the western United States, there has been a long history of planting fish into historically fishless mountain lakes for the purpose of recreational fishing. This practice can have detrimental effects to lake ecosystems, particularly amphibian populations. We compiled records of fish plantings into lakes on the Olympic Peninsula in western Washington State dating back to 1930. Our field study occurred primarily within the boundaries of Olympic National Park (OLYM), with three additional lakes sampled in adjacent Olympic National Forest lands. We used Environmental DNA (eDNA) to estimate the current distribution of fish and amphibians in 117 remote mountain lakes throughout 13 watersheds. For our study, we focused on the following ten species that occur in or have been introduced into high elevation mountain lakes in OLYM: Rainbow Trout (Oncorhynchus mykiss), Brook Trout (Salvelinus fontinalis), Coastal Cutthroat Trout (O. clarkii clarkii), Yellowstone Cutthroat Trout (O. virginalis bouvieri), Westslope Cutthroat Trout (O. clarkii lewisi), Cascades Frog (Rana cascadae), Western Toad (Anaxyrus boreas), Rough-Skinned Newt (Taricha granulosa), Northwestern Salamander (Ambystoma gracile), and Long-toed Salamander (Ambystoma macrodactylum). We also used GIS to estimate the physical characteristics of each mountain lake including elevation (meters; m), lake area (hectares; ha), and a measure of solar radiation (hours per year; hr yr-1). We conducted occupancy analyses of the eDNA data, physical attributes of the lakes, and planting history to determine the factors most responsible for the contemporary distribution of fish and amphibians in the sampled lakes. Our study showed the advantages of using eDNA to survey remote wilderness lakes to assess the current patterns of non-native fish and native amphibians. The non-invasive water sampling, highly sensitive detection, logistically efficient and relatively safe field work compared to traditional methods allowed us to conduct a broad survey across a large national park, much of it in remote and rugged wilderness terrain