2016 Research and Monitoring of Adult Oncorhynchus mykiss in the Nisqually River

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Published: September 2016

Pages: 21

Author(s): Gabe Madel and James P. Losee


Introduction

The Nisqually River originates from the Nisqually Glacier on the slopes of Mt. Rainier and drains 1,890 km2 of the westslope of the Cascade Range. The Nisqually River flows west-northwest approximately 125 km before draining into south Puget Sound northeast of Olympia, Washington. Rainfall, snowmelt, and glacial melt all contribute flow to the Nisqually River. The LaGrande (river km 68.0) and Alder hydroelectric projects (river km 71.0) both influence the flow regime and LaGrande Dam is the upstream boundary of anadromous salmonids. Downstream of LaGrande Dam, the Nisqually River flows through a mix of forested, rural, and agricultural land before bordering the Fort Lewis Military Reservation (river km 31.0 downstream to 4.0) and the Nisqually Indian Reservation (river km 17.6 to 8.6).

Puget Sound Steelhead Distinct Population Segment (DPS) was listed as threatened under the Endangered Species Act in 2007 (NMFS, 2007). Recovery of Puget Sound steelhead trout Oncorhynchus mykiss (O. mykiss) depends on identifying factors regulating the viability of the anadromous life history strategy (WDFW 2008). O. mykiss can exhibit a complex array of life history strategies, including both resident and anadromous forms (Courter et al. 2013; Kendall et al. 2015). Both anadromous (steelhead) and resident O. mykiss life history types are present in the Nisqually River. Numerous studies outside of the Nisqually River have shown that genetic exchange between the two life history types is not uncommon in sympatric populations (Docker and Heath 2003; McPhee et al. 2007; Pearsons et al. 2007) and some endemic populations of O. mykiss display partial anadromy (one gene pool displaying both anadromous and resident life histories) (Olsen et al. 2006; Arakee et al. 2007; McPhee et al. 2007). Understanding the relationship and degree of interaction between resident and anadromous O.mykiss in Puget Sound watersheds is important in making management decisions (i.e. habitat restoration, fishery regulations, and hatchery practices) that promote recovery of the species.

Historically, monitoring and management actions in the Nisqually River have focused on the anadromous population of O. mykiss, however the statewide steelhead management plan provides a directive to clarify the ecological relationship between resident and anadromous O. mykiss (WDFW 2008). In 2015 we used otolith microchemistry to estimate the maternal contribution of anadromous and resident life histories to O. mykiss in the Nisqually River. Results from analysis of otoliths collected from O.mykiss parr, smolts, and adult rainbow trout from various locations in the Nisqually River drainage highlighted the association resident O.mykiss have to their anadromous counterparts in the Nisqually River and reinforced the need to monitor both life histories (WDFW, in prep). The purpose of this document is to summarize stock assessment, monitoring and research activities conducted by Washington Department of Fish and Wildlife (WDFW), Nisqually Indian Tribe (NIT), and Joint Base Lewis McCord (JBLM) associated with adult Nisqually River winter O.mykiss in 2016.

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