Upper Yakima Basin Bull Trout eDNA

Connor Parrish collecting eDNA from the upper Cle Elum River- Photo credit: Daniel Suggs

Yakima River Basin Bull Trout

Bull trout (Salvelinus confluentus) are a native species of char that were once abundant throughout the cold streams of the Northwestern United States. Within these cold-water systems bull trout are an apex predator feeding on a host of fish including native salmonids.  Within their historic range and the Yakima River Basin their numbers have been greatly reduced due to issues associated with harvest, habitat loss, invasive species, reductions of their historic prey base, and climate change.

In 1998, bull trout were listed as a threatened species under the Endangered Species Act (ESA). There are 15 recognized bull trout populations in the Yakima Basin. According to the Washington Department of Fish and Wildlife, the status of these 15 populations range from healthy to potentially extirpated, raising questions about the current distribution of bull trout in the Yakima Basin. It is vital to gain a better understanding of the status of Yakima Basin bull trout populations to help prioritize recovery efforts.

A Cryptic Species

Bull trout have stringent habitat requirements including cold (<17 °C), clean water and access to complex, well-connected habitat. These requirements often restrict bull trout to headwater streams. The remote nature of these streams present challenges to collecting data on the current location of ESA listed bull trout. Traditional methods of snorkel surveys and electrofishing can be expensive, logistically challenging, and labor intensive. This has resulted in a lack of data confirming the current location of bull trout in the Yakima Basin and created challenges for local biologists attempting to recover this species.

Young-of-the-year bull trout in Gold Creek- Photo credit: Ashton Bunce

Environmental DNA

Environmental DNA (eDNA) is a relatively new survey technique that has the potential to provide information on the current location of bull trout within the Yakima Basin at a fraction of the cost and time of traditional methods. In its simplest form eDNA surveys consist of collecting small samples of DNA (naturally shed by organisms). This DNA is then replicated in a laboratory and tested for the presence of DNA from a desired species. Bull trout eDNA surveys involve 2-person crews filtering 5 liters of water from a desired location with minimal equipment (battery operated pump, sterilized sampling equipment). This allows for the rapid collection of eDNA samples that can help confirm the current distribution of bull trout within their historic range.

After water is pumped through the filter it is folded into quarters and preserved in a desiccant- Photo credit: Christian Hardt

Upper Yakima Bull Trout eDNA

The Yakima Bull Trout Working Group (BTWG) secured funding through the Yakima Basin Integrated Water Resource Management Plan in 2017 to conduct eDNA sampling in the upper Yakima Basin where bull trout occupancy and distribution is questionable and/or unknown. The 2015 US Fish and Wildlife Service Bull Trout Recovery Plan and 2012 Yakima Bull Trout Action Plan recognized 6 of the 15 Yakima Basin bull trout populations as residing in the Upper Yakima River. The status of these 6 populations range from critical to potentially extirpated making this region a priority for the initial implementation of eDNA surveys in the Yakima Basin.  

Field Work

The BTWG relied upon the knowledge of local biologists and the Climate Shield model created by the Rocky Mountain Research Station to prioritize eDNA sampling of streams in the Upper Yakima Basin. eDNA samples were collected from July through late September, 2017. Each sample location presented unique challenges. Some sites were easily accessible from Forest Service roads with others requiring extensive hiking and overnight trips. During the summer of 2017, the partnership between MCFEG, USFWS and USFS collected 347 eDNA samples in the Upper Yakima Basin.

Location of eDNA samples take in 2017

Data Analysis

Each sample was shipped to the USFS Rocky Mountain Research Station (RMRS) in Missoula, Montana. Once samples were received they were preserved until they could be processed. The RMRS is responsible for all data analysis and the development of a final report summarizing the findings of the 2017 Upper Yakima Basin eDNA sampling effort. The final report produced by the USFS Rocky Mountain Research Station is expected to be completed by spring 2018.