Salcha River Chinook Salmon Escapement

Chinook and chum salmon were visually enumerated from an elevated counting tower as they passed over a continuous band of white fabric panels that were strung across the river bottom. Two ARIS sonar units were placed on either side of the river, upstream of the counting tower to estimate the number of migrating salmon during extended periods of high, dirty water that precluded any visual counts (although sonars were operational during the whole season). While escapement estimates are still preliminary for 2019, we are confident that the Chinook salmon escapement goal was met for all years of this funding cycle: 2017 (4,195, SE = 205), 2018 (5,021, SE = 137) and 2019 (4,678 Chinook salmon). Chum salmon counts are considered to be incomplete because enumeration only occurs during the Chinook salmon run. Chinook salmon carcasses were sampled to estimate age, sex and length compositions of the escapement. A combined total of 1,141 Chinook salmon were sampled from 2017-2019 with the minimum length being 360 mm, max length being 970 mm and the average equaling 742 mm. The dominant age class for all fish for 2017 was 1.3, 1.4 for 2018, and 1.3 for 2019.

Chinook salmon bound for the Salcha River to spawn are harvested by subsistence users from Alakanuk to Tanana within the mainstem Yukon River and from Tanana to Nenana on the Tanana River tributary. This project will provide inseason information regarding Salcha River Chinook run strength that can be used to make management decisions regarding harvest opportunities, ensuring a sustainable escapement for future subsistence harvests. Continuing the series of escapement estimates on the Salcha River is also critical for evaluating the efficacy of management systems throughout the Yukon River drainage and for refining escapement goals by examining Chinook salmon productivity associated with different levels of escapement and environmental conditions. Including chum in the counting and carcass surveys both provides information on chum abundance and facilitates species differentiation when the sonar is utilized.