Use of PIT Tags to Determine Upstream Migratory Timing and Survival of Columbia Basin Sockeye Salmon in 2006
A total of 503 Sockeye Salmon, Oncorhynchus nerka, were PIT-tagged at Bonneville Dam in 2006 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 93.2% for Sockeye Salmon passing Bonneville Dam the week of June 11 to 63.8% for Sockeye Salmon passing the week of July 10. There was also a significant linear relationship between decreasing survival and decreasing flow as well as increasing water temperature. The estimated stock composition of Sockeye passing Bonneville Dam was 72.8% Okanogan and 27.2% Wenatchee. Sockeye Salmon mean travel time between Bonneville and Rock Island dams was 14 days, indicating a mean travel speed of 34.9 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 17.8% more fish at McNary and Priest Rapids dams, but up to 14.3% fewer fish at Rock Island, Rocky Reach, and Wells dams when compared to those made by visual fish counts at mainstem dams. Estimated rates of Sockeye Salmon falling back over the dams after ascending and then reascending ranged from 0.2% at Bonneville Dam to 3.3% at Wells Dam.
Fryer, J. 2007. Use of PIT tags to determine upstream migratory timing and survival of Columbia Basin Sockeye Salmon in 2006. Columbia River Inter-Tribal Fish Commission Technical Report 07-1, Portland, Oregon. 42p.