Oral presentation: Steelhead symposium
Understanding the Rock Creek, WA, steelhead population through the use of PIT tags and
genetic evaluation.
Brady Allen1, Elaine Harvey2, and Andrew Matala3
1U.S.
Geological Survey
Western Fisheries Research Center, Columbia River Research Laboratory
5501-a Cook-Underwood Rd.
Cook, WA 98672
Phone: 509-538-2299 x356 Email: ballen@usgs.gov
2
Yakama Nation Fisheries, Goldendale Field Office
P.O. Box 655
Goldendale, WA 98620
3
Columbia River Inter-Tribal Fish Commission, Hagerman Genetics Laboratory
3059F National Fish Hatchery Road
Hagerman, Idaho 83332
Phone: (208) 837-9096
Presenter: Brady Allen
Abstract: The U.S. Geological Survey collaborated with the Yakama Nation starting in fall of
2009 to study fish populations in Rock Creek, a southwest WA tributary of the Columbia River
21 kilometers upstream of John Day Dam. Prior to this study, little was known about the ESAlisted 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, identify
areas of high salmonid productivity, and document fish distribution, abundance, and movement.
We assessed the movement of fish into and out of Rock Creek by building, installing, and
operating two passive integrated transponder (PIT) tag interrogation systems at rkm 5 and rkm
13. We PIT-tagged 3,088 O. mykiss from fall 2009 to fall 2012. About 27% of those PIT-tagged
were detected outmigrating to the Columbia River. As of December 2013, nine fish that were
tagged in Rock Creek as juveniles have returned as adults to Bonneville Dam. In addition, 34
adult steelhead PIT-tagged by others have been detected in Rock Creek, of which, 22 were of
known origin. Of these, 85% were tagged or released in the Snake River and many (55%) were
barged as juveniles from Lower Granite Dam. Most (76%) of the adult steelhead eventually
entering Rock Creek first swam past it and were detected passing McNary Dam, 100-km
upstream. Representative samples from the O. mykiss were submitted to the Columbia River
Inter-Tribal Fish Commission for genetic analysis. Many individual fish were genetically
assigned to Rock Creek, which suggests that Rock Creek supports a distinct local population.
However, introgression by stray Snake River fish was prevalent and spatially distributed
throughout Rock Creek. These results have implications for the management of Rock Creek and
Snake River steelhead populations as well as McNary Dam.