Migratory Characteristics Of Spring Chinook Salmon In The Willamette River

This report documents our research to examine in detail the migration of juvenile and adult spring chinook salmon in the Willamette River. We seek to determine characteristics of seaward migration of spring chinook smolts in relation to oxygen supplementation practices at Willamette Hatchery, and to identify potential sources of adult spring chinook mortality in the Willamette River above Willamette Falls and use this information towards analysis of the study on efficiency of oxygen supplementation. The majority of juvenile spring chinook salmon released from Willamette hatchery in 1991 begin downstream movement immediately upon liberation. They travel at a rate of 1.25 to 3.5 miles per hour during the first 48 hours post-release. Considerably slower than the water velocities available to them. Juveniles feed actively during migration, primarily on aquatic insects. Na/K gill ATPase and cortisol are significantly reduced in juveniles reared in the third pass of the Michigan series with triple density and oxygen supplementation, suggesting that these fish were not as well developed as those reared under other treatments. Returning adult spring chinook salmon migrate upstream at an average rate of about 10 to 20 miles per day, but there is considerable between fish variation. Returning adults exhibit a high incidence of wandering in and out of the Willamette River system above and below Willamette Falls.