Report A: Fish distribution and population dynamics in Rock Creek, Klickitat County, Washington

The U.S. Geological Survey collaborated with the Yakama Nation starting in fall of 2009 to study the fish populations in Rock Creek, a Washington State tributary of the Columbia River 21 kilometers upstream of John Day Dam. Prior to this study, very little was known about the ESA-listed (threatened) Mid-Columbia River steelhead (Oncorhynchus mykiss) population in this arid watershed with intermittent stream flow. The objectives of the study were to quantify fish habitat, document fish distribution, abundance, and movement, and identify areas of high salmonid productivity. To accomplish these objectives, we electrofished in the spring and fall, documenting the distribution and relative abundance of all fish species to evaluate the influence of biotic factors on salmonid productivity and survival. We surveyed the distribution of perennial pools and established a network of automated temperature recording devices from river kilometer (rkm) 2 to 23 in Rock Creek and rkm 0 to 8 in Squaw Creek, a major tributary entering Rock Creek at rkm 13, to better understand the abiotic factors influencing the salmonid populations. Salmonid abundance estimates were conducted using a mark-recapture method in a systematic subsample of the perennial pools. The proportion and timing of salmonids migrating from these pools were assessed by building, installing, and operating two passive integrated transponder (PIT) tag interrogation systems at rkm 5 and at the confluence with Squaw Creek (rkm 13). From fall 2009 to fall 2012, we PIT-tagged 3,088 O. mykiss and 151 coho salmon (O. kisutch) during electrofishing efforts. In the lowest flow periods of 2010 to 2012, we found that an average of 36% of the surveyed streambed length was dry, and 17% remained as perennial pools. The maximum temperature recorded in those pools was 24.4°C, but most pools had a maximum temperature that was less than 21°C. O. mykiss were present in most pools, and non-native fish species, such as smallmouth bass (Micropterus dolomieu), were typically found downstream of rkm 5. Coho salmon were present in nearly every pool that was sampled in 2011, but were rare in 2009, 2010, and 2012. About 27% of the PIT-tagged O. mykiss and 38% of the PIT-tagged coho were detected outmigrating to the Columbia River. Of those fish, 92% (n=695) were detected leaving Rock Creek as smolts in April and May. As of November 2013, 9 O. mykiss and 4 coho that we tagged in Rock Creek as juveniles have returned as adults to Bonneville Dam. Also, an additional 34 PIT-tagged adult steelhead, and 6 PIT-tagged coho that were tagged by other groups have been detected in Rock Creek, of which, 22 were of known origin (tagged as juveniles). Of these, 85% were tagged or released in the Snake River. The PIT-tag interrogation systems will be operated for several more years to allow time for the fish tagged as juveniles to return as adults and complete their life cycles. The Yakama Nation will use the information collected from this study to prioritize and gauge the effectiveness of ongoing and future restoration actions.