|Document Type:||Contract Report|
|Title:||A study to define the migration characteristics of Chinook and coho salmon and steelhead in the Columbia River estuary (Annual report, 1979)|
|Author/Editor:||Earl M. Dawley, Carl W. Sims, Richard D. Ledgerwood, David R. Miller, Frank P. Thrower|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||Pacific Northwest Regional Commission|
1. Beach and purse seines in the upper estuary (rkm 75) and purse seines in the lower estuary (rkm 16) and Pacific Ocean near the Columbia River mouth were used to monitor smelt outmigration in 1979.
2. Catches of smelts in 1979 were slightly greater than in 1978.
3. By request, various biological samples were collected from adipose clipped fish for other researchers.
4. The period of maximum subyearling chinook salmon migration in 1979, based on Jones Beach recaptures, was in mid-July as compared to mid-May in 1977 and mid-June in 1978. The differences were related to hatchery releases and changes in catch ef ficiencies due to river flow.
5. Movement rate of chinook salmon decreased upon entry into the estuary. Residency in the Columbia River plume precluded precise measurements of movement rate into the ocean. Steelhead and coho salmon generally moved rapidly through the estuary and were not recaptured in the ocean.
6. Diel catch patterns at Jones Beach show a decrease at night for subyearling chinook and coho salmon, and steelhead. Patterns for yearling chinook salmon were inconclusive.
7. No significant differences were detected in recapture rates in 80 of 91 possible comparisons between replicate groups. Thus recapture rates generally could be compared between unlike groups, from the same stock, to obtain relative survival measurements.
8. Fish groups transported downstream past dams in the Columbia River basin showed relative increases of 20 to 1500% survival as compared to non-transported fish.
9. Coho salmon groups released in June and July showed a consistently higher relative survival rate than groups released in May.
10. Measurements of absolute survival for fall (subyearling) chinook salmon, from release site to the estuary, ranged from 19 to 62% for index stocks.
11. Adult returns in future years should provide information as to the precision of juvenile survival estimates to the estuary as a predictor of adult return rates.