Limiting Factors of the Abundance of Okanagan and Wenatchee Sockeye Salmon in 2010
A total of 913 sockeye salmon, Oncorhynchus nerka, were PIT tagged at Bonneville Dam in 2010. These fish were tracked upstream using data from 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 and Okanagan basins. Upstream survival steadily declined as the migration progressed; Bonneville-Rock Island survival declined from as much as 90% for sockeye salmon passing Bonneville Dam in early June to less than 75% 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 81.8% Okanagan 17.3% Wenatchee, and 0.9% Snake. The median travel time of sockeye salmon between Bonneville and Rock Island dams was 12.9 days, resulting in a median travel rate of 37.8 km per day. Fish passing Bonneville Dam later in the migration traveled upstream faster than those earlier in the migration. In the Okanagan Basin, PIT tag antennas were installed at Zosel Dam fish ladders on September 2, 2010. Between startup and March 31, a total of 27 sockeye, 10 Chinook, and 1 steelhead were detected. At Wells Dam, 400 PIT tags, 64 acoustic tags, and 52 temperature tags were deployed on 400 sockeye salmon. The detection rate at the Okanagan Channel PIT tag detection array (OKC) for fish only PIT tagged at Wells Dam was 73.7% compared to 70.7% for sockeye passing Wells Dam that we PIT tagged at Bonneville Dam. Sockeye with both PIT and acoustic tags were 25.8% less likely to be detected at OKC than those only PIT tagged, while sockeye with both PIT and temperature tags were 25.3% less likely to be detected at OKC. The OKC PIT tag array detected 90.2% sockeye with both an acoustic and PIT tag, while the OKC acoustic receiver detected 97.6% of these fish.
Fryer, J.K., H. Wright, S. Folks, and K. Hyatt. 2011. Limiting Factors of the Abundance of Okanagan and Wenatchee Sockeye Salmon in 2010. Columbia River Inter-Tribal Fish Commission Technical Report 11-04 for U.S. Dept. of Energy Bonneville Power Administration Project 2008-503-00. 82p.