Sonar Estimation of Summer Chum and Pink Salmon in the Anvik River, Alaska, 2021

Dual-frequency identification sonar (DIDSON) was used to estimate adult summer chum salmon (Oncorhynchus keta) and pink salmon (O. gorbuscha) passage in the Anvik River from June 15 to July 26, 2021. Apportionment to species was determined from data collected from tower counts. A total of 18,819 (SE 273) summer chum and 0 pink salmon were estimated to have passed the sonar site. A beach seine sample fishery was conducted to collect age, sex, and length information; however, high water prevented fishing for part of the season. In addition, because of low salmon passage, few fish were caught, and the sample fishery was discontinued early. Both sonar systems functioned well with minimal interruptions to operation. Range of ensonification was considered adequate for most fish that migrated upstream.