2016 Research and Monitoring of Adult Oncorhynchus Mykiss in the Puyallup and White Rivers

The Puyallup River flows westward more than 54 miles from the west and north slopes of Mount Rainier to Commencement Bay in South Puget Sound. The Puyallup River watershed encompasses 948 square miles (2,454 km²) and includes two major tributaries, the Carbon River and White River (Figure 1). The watershed as a whole contains a high proportion of urbanized, degraded habitat, multiple hydropower facilities, and an estuary that serves as one of the most active commercial ports in the world (Port of Tacoma).

Oncorhynchus mykiss (O.mykiss) originating from the Puyallup River watershed represent two distinct populations, Puyallup River steelhead and White River steelhead (Van Doornik et al. 2007) and are part of the Puget Sound Distinct Population Segment (DPS) which was listed as threatened under the Endangered Species Act (ESA) in 2007(NMFS, 2007). O. mykiss have been shown to express a variety of life history strategies including anadromous fish that undergo marine migrations and resident fish that complete their life cycle in fresh water (Kendall et al. 2015).

The Puyallup steelhead population is made up of natural spawners who utilize the Puyallup and Carbon mainstems but the majority of spawning occurs in the many tributaries. An accurate estimate of the total number of spawners utilizing the mainstem Puyallup River is unknown due to low visibility caused by glacial flour. Surveying effort throughout the watershed suggests that South Prairie Creek, a non-glacial Carbon River tributary, supports a high proportion of the total steelhead spawners.

While the majority of spawning on the White River occurs naturally above Mud Mountain Dam (rkm 47.6) a proportion of steelhead returning to the White River originate from a wild broodstock hatchery program that was started in 2006. The juveniles are reared and released from acclimation ponds located in the upper White River. These individuals are distinguishable from naturally produced fish through electronic detection of a blank coded wire tag.