Richard W. Zabel
James J. Anderson
and
Pamela Shaw
University of Washington
Box 355218
Seattle, WA 98195-5218
accepted by Canadian Journal of Fisheries and Aquatic Sciences
Abstract: A multiple reach model is developed to describe the downstream migration of juvenile salmonids in the Columbia River system. Migration rate for groups of fish is determined on a per reach and per time step basis. A nested sequence of nonlinear models is proposed to relate the variation in migration rates to river flow, date in season, and experience in the river. By comparing model predicted travel times to observed travel times to several observation sites along the migration route, the relative performance of the migration rate models can be assessed. The model is applied to cohorts of yearling chinook captured at the Snake River trap near Lewiston, Idaho and fitted with passive integrated transponder (PIT) tags over the eight year period 1989-1996. The fish were observed at Lower Granite and Little Goose Dams on the Snake River and Mcnary Dam on the Columbia River. The total length of the observed migration route is 277 km. The migratory data of these fish supports a model containing the following two behavioral components: a flow term that is related to season - fish spend more time in regions of higher river velocity later in the season; and a flow-independent experience effect where the fish migrate faster the longer they have been in the river.