|Document Type:||Contract Report|
|Title:||Migrational characteristics, biological observations, and relative survival of juvenile salmonids entering the Columbia River estuary, 1966-1983|
|Author/Editor:||Earl M. Dawley, Richard D. Ledgerwood, Theodore H. Blahm, Carl W. Sims, Joseph T. Durkin, Richard A. Kirn, Andris E. Rankis, Gerald E. Mohan, Frank J. Ossiander|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||Bonneville Power Administration. Portland, Oregon|
From 1966 to 1972, the Coastal Zone and Estuarine Studies Division of the Northwest and Alaska Fisheries Science Center developed and refined procedures for sampling juvenile salmon and steelhead entering the Columbia River estuary and ocean plume. Sampling of hatchery fish at the terminus of their freshwater migration was conducted to assist in evaluating hatchery production techniques and identifying migrational or behavioral characteristics that influence survival to and through the estuary.
Because of a lack of funds, no sampling was done from 1973 through 1976. From 1977 through 1983, the Northwest Regional Council and Bonneville Power Administration funded the estuarine sampling program to provide assessment of juvenile migrations from wild salmon stocks and from mitigation hatcheries experimenting with enhanced cultural procedures. The facilities or procedures implemented for safe juvenile salmonid passage at dams and through reservoirs were also evaluated. Extensive fish marking programs by state and federal fishery agencies provided the capability to assess migrational behavior and relative survival of identifiable hatchery and wild stocks. Fall chinook salmon (subyearlings) in particular provided a consistent and thorough index because of intensive marking programs to assess stock contributions.
The Columbia River estuary sampling program was unique in attempting to estimate survival of different stocks and define various aspects of migratory behavior in a large river, with flows during the spring freshet of 4,000 to 17,000 m3/second. Previous knowledge of estuarine sampling for juvenile salmonids was limited to several small river systems and the evaluation of movement behavior, residence times, and feeding behavior.
During our initial research (1966-1972), various fishing methods (fyke, trawl, gill, and seine nets) were used at many locations throughout the estuary. Procedures and sites used during 1977-1980 and 1981-1983 were adopted from earlier work with the extension of sampling sites into marine waters adjacent to the mouth of the Columbia River.