|Document Type:||Contract Report|
|Title:||Migrational characteristics and survival of juvenile salmonids entering the Columbia River estuary during 1982|
|Author/Editor:||Earl M. Dawley, Richard D. Ledgerwood, Theodore H. Blahm, Richard A. Kirn, Andris E. Rankis, Frank J. Ossiander|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||Bonneville Power Administration. Portland, Oregon|
We conducted sampling related to migrational behavior and relative survival of juvenile salmonids Oncorhynchus spp. entering the Columbia River estuary. Beach and purse seines were used at Jones Beach (rkm 75) from March through September and November through mid-December 1982. During the peak migration (May and June), 10 beach–seine sets and 5 purse–seine sets were made daily beginning at sunrise and continuing for 7 h. Total salmonid catch was 229,301 fish, of which 5.0% were marked. Based on two independent methods used to calculate the effect of river flow on catch, an increase of 1,000 m3/s in river flow decreased catch by an estimated 8 or 12%.
Temporal distributions of juvenile salmon and steelhead in 1982 were similar to previous years, with peak catches generally corresponding to dates of hatchery release rather than factors such as river flow or temperature. Peak migration was during the third week of May for yearling Chinook salmon and the fourth week of May for steelhead and coho salmon; these peaks occurred about 2 weeks later in 1982 than 1981. Four peaks were noted for subyearling Chinook salmon: early April, first week of May, mid-June, and early July.
Movement rates were slowest for groups that wintered in the Columbia River or its tributaries and small subyearling Chinook salmon released after mid-June.
Two independent comparisons showed that the migration of juvenile hatchery fall Chinook was apparently more successful in 1982 than in recent years.
Relative differences in survival were observed for: 1. subyearling chinook salmon from Bonneville and Spring Creek Hatcheries transported upstream and released in the Umatilla River compared to controls released at their respective hatchery; 2. subyearling chinook salmon transported from McNary Dam and released downstream from Bonneville Dam, compared to controls which migrated through the bypassed section of river; and 3. A vs. B stock steelhead reared at Hagerman Hatchery.