Detection and Range Delineation of Bull Trout Using Environmental DNA
Bull trout are a critical component of aquatic community assemblages, and a focal species for the Great Northern Landscape Conservation Cooperative in all four ecotypic areas: the Columbia Basin, Rocky Mountains, Sagebrush Steppe, and Cascadia. This species is listed as an endangered species and occurs at low densities within thousands of streams designated as critical habitat across the region. Mounting evidence shows that the distribution of bull trout within individuals streams has been contracting in association with climate change; some historically occupied habitats may no longer support populations. Because of the difficulty and expense of sampling bull trout, current information about the species distribution is imprecise and many streams have been sampled infrequently or not at all. To reduce uncertainties (and regulatory gridlock) associated with bull trout, Forest Service scientists recently developed and published the Climate Shield Habitat Occupancy Model, which usesNorWeST temperature information and other environmental covariates to accurately predict the probability of bull trout (and cutthroat trout) presence across the Columbia Basin.. The fish and temperature data used to develop the NorWeST and Climate Shield databases and models were “crowd-sourced.” That approach was particularly powerful because it engaged hundreds of biologists working for dozens of agencies and leveraged their raw data to develop databases worth more than $10,000,000. Building on those efforts, the scientists plan to conduct a precise, up-to-date, range-wide bull trout status assessment through the use of the above described crowd-sourcing, digital media, and new genomic techniques that are revolutionizing the cost-effectiveness of broad-scale species sampling.
Among the array of genomic techniques now available, environmental DNA (eDNA) has emerged as a powerful method for determining the occurrence of many species reliably and inexpensively. The method involves collecting DNA shed by organisms (i.e., environmental DNA) by pumping water through a filter. The scientists have also developed a field-proven eDNA sampling protocol that requires only 15 minutes of effort by a single person to collect a sample.
For bull trout, initial studies with eDNA have been directed at precisely delineating their distribution within select watersheds, as well as confirming their absence from potential habitats and discovering previously unknown populations.Samples collected to evaluate bull trout distributions can be used to evaluate many other species with no additional field costs and can serve as a multi-species baseline for future biodiversity assessments.
Forest Service Partners