Migration Survival of Okanagan and Wenatchee Sockeye Salmon

                In 20 years the number of Columbia Basin sockeye salmon counted at Bonneville Dam has increased from a record low of fewer than 8774 fish in 1995 to a record high of over 614,179 fish in 2014.  The past seven years have seen the 3 largest, and 7 of the top 10, runs on record.  Over this period, about 80% of this run has originated over 900 km upstream in the Okanagan Basin, Canada, with the bulk of the remaining sockeye from the Wenatchee Basin with nearly as long a migration. 

                In recent years, PIT tagging of both adults and juveniles, combined with an extensive PIT tag detection infrastructure in Columbia Basin dams and some acoustic tagging of adults, have provided detailed data on sockeye migration both downstream and upstream.  This data suggests survival from tagging to McNary Dam (at river km 500) of about 40% for juveniles, and survival for adults of under 50% from Bonneville Dam to the spawning areas in the Okanagan and Wenatchee basins.  This mortality over only a part of the migration suggests high ocean survival and in-basin productivity are likely major factors in the resurgence of sockeye in the basin.