Summary of Abundance and Biological Data Collected During Juvenile Salmonid Monitoring in the Mainstem Klamath River Below Iron Gate Dam, California, 2022

This report summarizes results from monitoring the outmigration of juvenile salmonids downstream of Iron Gate Dam on the mainstem Klamath River, California in 2022. rapping occurred at four locations: below the confluence with Bogus Creek (river km 308), just upstream of the Interstate 5 bridge (river km 294), upstream of the confluence with the Scott River near Kinsman Creek (river km 238), and above the confluence with the Trinity River near Weitchpec, California (river km 65). Both frame nets and rotary screw traps were deployed in early March and operated until early July. Traps were operated four nights each week from Monday to Friday. All juvenile salmonids in the catch were counted and each day a subset was measured for length, weight, and external symptoms of disease. Non-salmonid fishes in the catch were also enumerated and subsampled to measure length. Mark-recapture studies were conducted periodically at the I-5, Kinsman and Weitchpec trap sites during the season to estimate trap efficiency. Efficiency estimates and catch data were used to estimate weekly and seasonal outmigration abundance of age-0 juvenile Chinook Salmon migrating downstream past the I-5, Kinsman, and Weitchpec trap sites using a Bayesian time-stratified population estimation method. Due to an early release (April 15) of 2.8 million unmarked hatchery-origin juvenile Chinook Salmon, abundance estimates in 2022 represent combined hatchery- and natural-origin stocks. For the periods that traps were operated, season-wide abundance estimates of combined hatchery- and natural-origin age-0 Chinook Salmon were 5,936,109 (CI=4,199,753-8,179,567) at the I-5 trap site, 967,444 (CI=743,242-1,236,325) at the Kinsman trap site, and 1,384,187 (CI=811,879-2,222,750) at the Weitchpec site. Abundance estimates were not calculated for the Bogus trap site in 2022.