Project Title:  Evaluate Factors Limiting Columbia River Gorge Chum Salmon Populations

Contract Background and purpose:

Historically, chum salmon (Oncorhynchus keta) had the widest distribution of all Pacific salmon species, comprising up to 50% of annual biomass of the seven species and may have spawned as far up the Columbia River drainage as the Walla Walla River (Nehlsen et al. 1991).    Declines in the status of chum salmon and threats to the species prompted NOAA-Fisheries (formally the National Marine Fisheries Service (NMFS)) to list the Columbia River chum salmon Evolutionary Significant Unit as threatened under the Endangered Species Act on 24 May 1999 (NMFS 1999).  One of the primary factors contributing to the decline of chum salmon in the basin is degradation of freshwater habitats, which chum salmon use for spawning and early rearing.  Thus, efforts to conserve chum salmon have focused on investigating freshwater habitat relations, management activities that provide spawning habitat conducive to successful reproduction, and chum salmon status.  The original, and current, need for this project is to provide information on abundance of various life stages of chum salmon and habitat.  Abundance estimates are essential for assessing status, evaluating biological and physical factors potentially influencing production, and developing restoration actions.

Currently, chum salmon are primarily limited to the tributaries downstream of Bonneville Dam and the majority of the fish spawn in Washington tributaries of the Columbia River.  The only known stable, natural chum salmon production occurs in the Grays River (Gorley Creek), Hamilton Creek, and Hardy Creek (CBFWA 1990, Washington Department of Fisheries (WDF) et al. 1993).  Hardy and Hamilton creeks are the farthest upstream populations at river kilometer (rkm) 227 (Bonneville Dam is rkm 232), separated by over 160 rkm from the Grays River.  Chum salmon spawn in a side channel of the Columbia River located between Hardy and Hamilton creeks, near Ives Island ("Pierce/Ives Island Complex"), but the extent of spawning and production is not known.

Chum salmon from Hardy and Hamilton creeks have been placed in the Lower Columbia River Chum Evolutionary Significant Unit (ESU) (see NOAA 2005a).  Salmon from these creeks reside in the Gorge ecological zone and are the sole source of abundance and trend information for lower Gorge tributaries.  The time series used by NMFS for analysis of the Lower Gorge population of chum is based on summing the abundance information for Hardy and Hamilton creeks along with fish that spawn in the mainstem near the mouths of these tributaries (NOAA 2005a).  The number and relative proportion of chum that spawn in the tributaries and mainstem varies by year and environmental conditions.  Therefore, counts of adults in both areas are necessary to assess overall population abundance.  While the current viability status of chum from the Lower Gorge Tributaries is extremely low (see NOAA 2005a), recovery planning requires that this population of fish become viable (see NOAA 2005b).

BPA committed funding to this project beginning in FY2000, primarily as a monitoring effort to address three broad objectives:  1) examine factors limiting chum salmon production in Hardy Creek and Hamilton Springs, 2) enhance and restore chum salmon production, and 3) evaluate relationships between chum salmon spawning in the mainstem Columbia River and those in the two tributaries.  To examine factors limiting chum salmon production in Hardy Creek and Hamilton Springs, the abundance of adults and juveniles has been estimated since fall 1999.  Biological (e.g., age and sex composition of adults and size of juveniles) and behavioral (e.g., dates of immigration of adults and emigration of juveniles) characteristics have been recorded to describe adult and juvenile fish annually.  Habitat features (e.g., redd location, water temperature, discharge, substrate composition, subsurface water characteristics) have been recorded.  In addition, recently emerged juveniles have been collected from individual redds.

Data generated by this project has been routinely sent to the Fish Passage Center to update adult and juvenile databases, and made available upon request to other entities (e.g., the Technical Management Team, members of NOAA’a Technical Recovery Team, and those involved in subbasin planning).  Data summaries and results have been presented in annual and quarterly reports, presentations at professional meetings, a presentation to CBFWA’s Anadromous Fish Committee, and in house seminars.  Data has also been shared with others working on chum salmon in the basin (e.g., WDFW, PSFMC) to contribute to other specific projects and abundance estimates throughout the basin.

We have been able to generate estimates of abundance, describe biological and behavior characteristics of adult and juvenile chum salmon, and characterize spawning habitat.  Now that we have a time series, particularly of abundance estimates for various developmental stages, a comprehensive inspection of all data collected to date is needed.  This will allow us to specifically assess factors and developmental stages that may be limiting, examine the trend in population abundance, and calculate population growth rate.  Continued work on the project is strongly justified.  It not only provides abundance estimates for a portion of the basin, but has established a time series that should be continued to more fully address factors influencing production, track status, and develop potential management actions to enhance production.


FY 07 Project objectives

1. Determine abundance and biological characteristics of adult chum salmon

2. Assess habitat parameters associated with chum salmon spawning

3. Determine the number of potential eggs deposited by adult chum salmon

4. Determine the rate and estimate the number of chum salmon fry that emerge

5. Determine the production and abundance of chum smolts as well as their biological characteristics:

6. Determine population growth rate and assess limiting factors for chum salmon