|Title:||Migrations of juvenile coho salmon, Oncorhynchus kisutch, into the Columbia River estuary, 1966-71|
|Author/Editor:||Joseph T. Durkin, Carl W. Sims|
|Institution:||National Marine Fisheries Service, Northwest and Alaska Fisheries Science Center. Report of the Coastal Zone and Estuarine Studies Division|
Beach–seine sampling of juvenile coho salmon, Oncorhynchus kisutch, in the lower Columbia River is described for 1966 through 1971. Major migrations into the estuary occurred between late April and late May in each year of the study; peak catches occurred between 6 and 16 May. Release of marked hatchery fish at various upriver sites indicated that movement and recovery rates of downstream migrants in the estuary were related to time of release and distance from the estuary. Recoveries of individual groups of marked coho salmon released from March to May at Ice Harbor Dam in 1967 and 1968 revealed that later releases moved downstream more swiftly than did early releases. Length frequency data show that larger coho salmon (>125 mm) arrived in the estuary first and that progressively smaller coho salmon arrive after the peak of migration. The average size of coho salmon increased during the 6 years of this study. Relations between hatchery practices, movement, and size of fish entering the estuary are discussed.