|Document Type:||Contract Report|
|Title:||Migrational characteristics and survival of juvenile salmonids entering the Columbia River estuary in 1981|
|Author/Editor:||Earl M. Dawley, Richard D. Ledgerwood, Theodore H. Blahm, Alvin L. Jensen|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||Bonneville Power Administration. Portland, Oregon|
With funding from the Bonneville Power Administration, the National Marine Fisheries Service conducted a study related to migrational behavior and survival of juvenile salmonids Oncorhynchus spp. entering the Columbia River estuary. Beach and purse seines were used to sample at Jones Beach (rkm 75) from March through November 1981. The total salmonid catch was approximately 200,000 fish, of which 3.3% were marked.
Migration peaks for hatchery yearling Chinook and coho salmon and steelhead trout occurred during early May, whereas three peaks were recorded for subyearling Chinook salmon during April, May, and July. Movement rates were slowest for three groups: 1. those that had overwintered in the Columbia River or its tributaries, 2. yearling chinook salmon released in March and April, and 3. small subyearling chinook salmon released throughout spring and summer. Movement rates to the estuary generally increased with increasing river flow and fish size.
Survival rates to the estuary were increased by transportation. Estimated survival rates of transported groups (relative to controls) increased proportionately with the numbers of dams bypassed, averaging 56% for one dam and 311% for eight dams.
Sampling effort at Jones Beach provided survival estimates studies of salmonid nutrition, rearing density, and chemical treatment.