|Document Type:||Contract Report|
|Title:||Migrational characteristics and survival of juvenile salmonids entering the Columbia River estuary during 1983|
|Author/Editor:||Earl M. Dawley, Richard D. Ledgerwood, Theodore H. Blahm, Richard A. Kirn, Andris E. Rankis|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||Bonneville Power Administration. Portland, Oregon|
Sampling of juvenile salmonids migrating into the Columbia River estuary was conducted in 1983 to evaluate behavior and survival and amass information important to restoration enhancement and protection of salmon. Beach and purse seines were fished at Jones Beach (rkm 75) in November and December 1982, late January to September 1983, and October through December 1983. In 1983, the total juvenile salmonid catch was 210,754 fish, of which 4.6% had marks. Summaries of mark recoveries with date range, average fork length, condition factor, and movement rate are presented in appendices.
Updated evaluation of sampling efficiency changes in relation to river flow showed an average of 11% decrease in catch per 1,000 m3/s increase in flow. Catch adjustment for different river flows is important for comparisons between groups captured at different times. Fall-released hatchery fish generally migrated past Jones Beach in fall, but large percentages of a few groups, often the smaller fish, overwintered in areas upstream from Jones Beach and migrated the following spring.
Temporal distribution of spring and summer migrants in 1983 was similar to previous years. Peaks migrations past Jones Beach were 7-13 May for yearling Chinook, 14-20 May for coho, and 21-27 May for steelhead. Three peaks in migration were observed for subyearling Chinook salmon: 4-20 May, 6-10 June, and 2-8 July.
We also evaluated survival rates between treatment and reference groups of marked fish. For coho and yearling Chinook salmon, test groups released at a later date had higher rates of survival than reference groups. Fall Chinook salmon fed a diet high in salt concentration also had higher survival than reference groups. Higher survival was also seen in coho salmon from Eagle Creek NFH reared at lower densities than reference groups and in Chinook salmon and steelhead transported and released below Bonneville Dam.
Variation of adult recovery data among replicate mark groups showed a need for more in-depth documentation of rearing and release information prior to using adult recovery data to evaluate the significance of variations of juvenile catches.