Use of PIT Tags to Determine Upstream Migratory Timing and Survival of Columbia Basin Sockeye Salmon in 2008
A total of 1133 sockeye salmon, Oncorhynchus nerka, were PIT-tagged at Bonneville Dam in 2008, 824 with 12.5 mm PIT tags (model TX1411SST) and 309 with 8.5 mm PIT tags (model TXP148511B). These fish were tracked upstream using detections within fish ladders at Bonneville, McNary, Priest Rapids, Rock Island, Rocky Reach, Wells, Ice Harbor, Lower Granite, and Tumwater Dams. Results indicated that 8.5 mm PIT tags were commonly not detected by fish ladder antennas at several dams and thus excluded 8.5 mm tag data from further analysis. Based on 12.5 mm tag detections, 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 then 80% 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 salmon passing Bonneville Dam was 87.4% Okanogan 12.3% Wenatchee, and 0.4% Snake.
Sockeye salmon mean travel time between Bonneville and Rock Island Dams was 14.0 days, indicating a mean travel speed of 35.1 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 29.9% more fish at McNary Dam than visual counts but estimates at other Columbia River dams were within 6.4% of visual counts. At Tumwater Dam, mark-recapture techniques estimated 29.1% fewer fish than visual counts. The mean time required from first detection to last detection for the same fish at Tumwater Dam was more than four days, compared with less than 10 minutes at mainstem dams other than Bonneville Dam (103 minutes) and Lower Granite Dam (490 minutes). Estimated rates of sockeye salmon falling back over the dams after ascending and then reascending (where n>10) ranged from 0.5% at Bonneville Dam to 4.0% at Rocky Reach Dam.
Fryer, J.K. 2009. Use of PIT Tags to Determine Upstream Migratory Timing and Survival of Columbia Basin Sockeye Salmon in 2008. Columbia River Inter-Tribal Fish Commission Report 09-03. 43p.