Gulkana River Chinook Salmon Escapement Estimation 2022 2026 PDF Download

Chinook salmon were radiotagged near the confluence of the Gulkana and Copper rivers from 2013-2015 to determine run timing and spawning distribution in the Gulkana River. The main goal was estimating what proportion of the Chinook salmon escapement spawned above an ADF&G operated counting tower located approximately 79.5 rkm up the Gulkana River. Age, sex, and length composition of the escapement was also estimated. A total of 412 Chinook salmon were radiotagged from 2013?2015 using dip nets and hook and line as capture gear. The proportion of Chinook salmon that spawned above the ADF&G counting tower was 0.51 (SE = 0.072) in 2013, 0.45 (SE = 0.073) in 2014, and 0.54 (SE = 0.038) in 2015. Fish spawning above the ADF&G counting tower had a slightly earlier run timing than fish spawning below the counting tower with annual mean dates of passage past the lowest inriver tracking station being 0?7 days earlier. Further examining run timing by river reach, Chinook salmon that spawned in the tributaries and upper mainstem of the Gulkana River had earlier run timing than those spawning in the middle to lower mainstem. The estimated percentage of females that spawned above the counting tower varied by year. Females comprised an estimated 53% (SE = 6%) of the escapement in 2013, 29% (SE = 10%) in 2014, and 51% (SE = 4%) in 2015. Age-1.3 Chinook salmon was the most abundant age class, accounting for 81% (SE = 5%) of the estimated escapement in 2013, 48% (SE = 6%) in 2014, and 88% (SE = 3%) in 2015. Chinook salmon in the length class 751-850 mm mid eye to tail fork accounted for the majority of the estimated annual escapement, ranging between 46% (SE = 6%) and 63% (SE = 4%). This study found several positive relationships with fish traits (e.g., sex, length, and run timing) and spawning success specific to the Gulkana River. Male fish, longer fish, and fish with earlier run timings all had better chances of spawning during this study.