Fish and habitat assessment in Rock Creek, Klickitat County, Washington 2016–17

Executive Summary

Intermittent streams are important and productive for salmonid habitat. Rock Creek, in southeastern Washington, flows south to the Columbia River at river kilometer (rkm) 368 and is an intermittent stream of great significance to the Yakama Nation and to the Kah-miltpah (Rock Creek) Band in particular. Historically, native steelhead (anadromous form of rainbow trout [Oncorhynchus mykiss]) and bridgelip sucker (Catostomus columbianus) populations were used by the Kah-miltpah Band for sustenance, trade, and traditional practices. Anadromous salmonid populations currently present and being monitored in the Rock Creek subbasin include Coho (O. kisutch) salmon and steelhead. Resident rainbow trout are also present and monitored (rainbow trout and steelhead will be collectively referred to as O. mykiss throughout this report). Streamflow is a limiting habitat factor in this system, but despite this, steelhead and Coho salmon still successfully return to spawn, rear, out-migrate, and survive over-summer in many of the isolated pools.

We completed habitat surveys during 2015–17 to assess the perennial pools during low-flow conditions. The lower river sections (rkm 2–13) had proportionately more dry sections than the upper river sections (rkm 14–22) for all years surveyed and had higher variability among habitat types across years. The surveyed dry sections within the lower river ranged from 44 to 57 percent, with 2015 (a drought year) as the highest and 2017 the lowest. The percentage of pool habitat in the lower river was 21−24 percent, with 2015 as the lowest and 2016 and 2017 both at 24 percent. The upper river sections had a relatively high percentage of non-pool wet habitat (49−51 percent), followed by dry (33−36 percent) and pool habitat (17−18 percent). In Walaluuks Creek, the percentage of pool habitat was the most consistent across the years, ranging from 10 to 13 percent.