Northwest Fisheries Science Center

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Document Type: Chapter or Section
Center: NWFSC
Document ID: 7698
Type of Book: Technical
Section or Chapter Title: Techniques for appraising adult salmon and trout populations in the Columbia River Basin
Book Title: Symposium on methodology for the survey, monitoring, and appraisal of fishery resources in lakes and large rivers. 2-4 May 1974, Aviemore, Scotland
Author: Parker S. Trefethen, Gerald B. Collins
Publication Year: 1974
Publisher: Food and Agriculture Organization of the United Nations (FAO)
Pages: 490-501

Appraisal of adult Pacific salmon Oncorhynchus spp. and steelhead trout Salmo gairdneri populations in the Columbia River Basin is made at dams and supplemented by pawning ground surveys.  Trained observers enumerate individual species of anadromous fish as they pass through fishways installed at most dams on the Columbia and Snake Rivers.  A promising technique being field-tested involves closed-circuit television:  migrating fish can be viewed on a television receiver and can be recorded for later review.  Aerial surveys in larger rivers and ground surveys in smaller tributaries provide data on spawning populations.

Estimates of some specially treated populations of salmon and trout are made by mark and recovery techniques to determine their survival to maturity.  Young fish are tagged during their seaward migration with magnetic color-coded wire tags and marked with cold brands; when they return as adults, the tagged fish are obtained from a fishway by an automatic recovery system.  The brands identify test and control lots of fish released in previous years.

Notes: A copy of author's original manuscript is attached to this record.