Studies into Factors Limiting the Abundance of Okanagan and Wenatchee Sockeye Salmon in 2009
A total of 850 sockeye salmon, Oncorhynchus nerka, were PIT tagged at Bonneville Dam in 2009. These fish were tracked upstream using detections at detection arrays within fish ladders at Bonneville, McNary, Priest Rapids, Rock Island, Rocky Reach, Wells, Ice Harbor, Lower Granite, and Tumwater dams as well as in-river arrays in the Wenatchee basin. Upstream survival steadily declined as the migration progressed; Bonneville-Rock Island survival declined from as much as 90% for sockeye salmon passing Bonneville Dam during June to less than 80% during July. There was also a significant linear relationship between decreasing survival and increasing water temperature. The estimated stock composition of sockeye salmon passing Bonneville Dam was 82.6% Okanagan 15.1% Wenatchee, and 2.3% Snake. The mean travel time of sockeye salmon between Bonneville and Rock Island dams was 12.7 days, indicating a mean travel speed of 38.2 km per day. Fish passing Bonneville Dam later in the migration traveled upstream faster than those earlier in the migration. In the Okanagan Basin, a PIT tag detection array was installed upstream of Osoyoos Lake and an acoustic receiver network installed to detect VEMCO tags placed in 50 sockeye salmon trapped at Wells Dam. Of these fish, 25 were detected at Zosel Dam and 21 entered the north basin of Osoyoos Lake. High water temperatures and delays at Zosel Dam appeared to be implicated in the demise of the four fish not detected past Zosel Dam.
Fryer, J.K., J. Mainord, H. Wright, S. Folks, and K. Hyatt. 2010. Studies into Factors Limiting the Abundance of Okanagan and Wenatchee Sockeye Salmon. Columbia River Inter-Tribal Fish Commission Technical Report 10-09 for U.S. Dept. of Energy Bonneville Power Administration Project 2008-503-00. 54p.