Use of PIT tags to Determine Upstream Migratory Timing and Survival of Columbia Basin Sockeye Salmon in 2007
A total of 509 sockeye salmon, Oncorhynchus nerka, were PIT-tagged at Bonneville Dam in 2007 and tracked upstream using detections at mainstem dam fish ladders. Based on these detections, upstream survival steadily declined as the migration progressed; Bonneville-Rock Island survival declined from over74% for sockeye salmon passing Bonneville Dam during June to less then 68% during the first two weeks of July. There was also a significant linear relationship between decreasing survival and increasing water temperature. The estimated stock composition of sockeye passing Bonneville Dam was 85.3% Okanogan and 14.7% Wenatchee. Sockeye salmon mean travel time between Bonneville and Rock Island dams was 14.6 days, indicating a mean travel speed of 33.2 km per day. Fish passing Bonneville Dam later in the migration traveled upstream faster than those earlier in the migration. Mark-recapture techniques were used to estimate sockeye salmon abundance at upstream dams. These techniques estimated up to 14.7% more fish at McNary Dam but at all other dams estimated 21.9% to 32.1% fewer sockeye salmon than indicated by visual dam counts. Estimated rates of sockeye salmon falling back over the dams after ascending and then reascending ranged from 0.2% at McNary Dam to 3.0% at Priest Rapids Dam.
Fryer, J.K. 2008. Use of PIT Tags to Determine Upstream Migratory Timing and Survival of Columbia Basin Sockeye Salmon in 2007. Columbia River Inter-Tribal Fish Commission Technical Report 08-02, Portland, Oregon. 41p.