Is There a Native Chinook Salmon Population in Crab Creek, a Desert Stream in Eastern Washington?

In 2006 the Washington State legislature authorized the Department of Ecology to create the Office of the Columbia River that was tasked to find sources of water for increased residential and agricultural demands.  Various options have since been proposed and all options will alter the water operations within the Columbia Basin Irrigation Project.  Although, many of sites proposed to be altered are non-natural aquatic systems, one site, Lower Crab Creek located in eastern Washington, is a natural, groundwater-fed tributary to the Columbia River at river kilometer 661.  Consequently, managers initiated a project to assess the aquatic ecosystem of LCC to predict possible impacts on LCC biota.  Although the creek was thought to be unsuitable for salmonids the project was to focus on habitat and water quality and to verify the presence of steelhead trout that had been previously reported in LCC.  Secondarily, the project was to assess Chinook salmon that had been observed in LCC but were thought to be strays.  During the three year study, no adult steelhead trout were observed or captured on the spawning grounds or the resistance board trap site, respectively.  However, Chinook salmon were captured in our upstream and downstream traps and observed in spawning locations.  Tissue samples were obtained for genetic analysis and compared to Chinook salmon collections in the GAPS database from interior Columbia Basin hatchery and wild populations.  LCC Chinook salmon were significantly different from all other Columbia Basin Chinook salmon populations, and had alleles that were absent from proximal Chinook salmon populations.  LCC Chinook salmon showed no evidence of recent founding and had similar genetic diversity, allelic richness and effective population size as other Columbia Basin Chinook salmon.  The data suggested that a genetically distinct, native population of Chinook salmon inhabits LCC that has likely adapted to the rigorous environment.  The potential for a newly described population of Chinook salmon in the Columbia Basin warrants additional monitoring and evaluation in order to better determine the status of this population.