Fall Chinook Salmon in the South Fork Coos River: Spawner Escapement, Run Reconstruction and Survey Calibration, 1998 - 2000, Information Reports 2003-02

Identification Information

Citation

Originator: Riggers, B., White, J., Hogansen, M., Jacobs, S., Weeks, H.

Publish Date: June 2003

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Cedric Cooney

Job Position: Natural Resources Data and Systems Manager

Telephone: 503-947-6094

E-Mail Address: cedric.x.cooney@odfw.oregon.gov

Description

Abstract: The Oregon Department of Fish and Wildlife (ODFW) has conducted a three year study designed to develop methods that provide reliable estimates of fall chinook salmon (Oncorhynchus tshawytscha) spawner escapements for the South Fork Coos River. This study is part of a larger effort to develop similar high-quality escapement estimates for fall chinook in Oregon coastal basins in order to meet Oregon’s Pacific Salmon Treaty monitoring responsibilities. Funding for this study was provided by the U.S. Section of the Chinook Technical Committee (CTC) of the Pacific Salmon Commission (PSC) pursuant to the 1999 Letter of Agreement (LOA). Three stock aggregates have been identified that originate from Oregon coastal basins. These aggregates are thought to represent distinct genetic and behavioral characteristics and are managed separately. The North Oregon Coast (NOC) and Mid Oregon Coast (MOC) are the two stock aggregates that are north migrating, and are subjected to the PSC’s abundance-based management program (USCTC 1997). The South Fork Coos River is one component of the MOC aggregate. Current monitoring programs for Oregon coastal fall chinook do not supply the CTC with adequate information that is required for the management and rebuilding of Oregon’s coastal chinook stocks. ODFW has conducted standard surveys for more than 50 years to monitor the status of chinook stocks along coastal Oregon (Jacobs et al. 2000). A total of 56 standard index spawner surveys (45.8 miles) are monitored throughout 1,500 stream miles on an annual basis to estimate peak escapement levels and track trends of northmigrating stocks. Although counts in these standard surveys may be sufficient to index long-term trends of spawner abundance, they are considered inadequate for deriving reliable annual estimates of spawner escapement for several reasons. These surveys were not selected randomly and cannot be considered representative of coast-wide spawning habitat. Also, fall chinook are known to spawn extensively in mainstem reaches and large tributaries, which are not conducive to the foot surveys. To provide estimates of escapements, index counts must be calibrated to known population levels. Obtaining accurate estimates of fall chinook spawner density in mainstem reaches is extremely difficult. Typically, these areas exhibit wide variations in stream flow and turbidity that create difficult and sometimes dangerous survey conditions resulting in unreliable visual counts. The goal of this project is to develop precise estimates of adult spawner escapement in the South Fork Coos River and to identify survey methods that can be used to reliably index spawner abundance for the South Fork Coos River and MOC stock aggregate. ODFW conducted mark-recapture experiments to estimate fall chinook spawning escapement in the South Fork Coos River from 1998 through 2000. We conducted foot and float surveys to obtain counts of live fish, carcasses, and redds. These indices are assessed against the mark-recapture estimates to determine whether any of them track fall chinook spawner abundance with sufficient precision to form the basis for long-term monitoring and the incorporation of resulting escapement estimates into PSC harvest modeling efforts. We used radio-telemetry as an independent method to estimate the distribution of fall chinook spawners between mainstem and tributary strata.

Purpose:

Time Period of Content:

Geographic Extent: Coos River, South Fork

Status: Final

Use Constraints:

Format: PDF File

Data Quality Information

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Data Information

No data information was supplied.

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Attributes Description: Field attribute information is available in the attached file(s).

Is a physical copy maintained for reference at Headquarters? No