Shasta River Salmonid Monitoring 2020 Siskiyou County, CA

A total of 4,168 fall run Chinook Salmon (Oncorhynchus tshawytscha) were estimated to have entered the Shasta River during the 2020 spawning season. An underwater video camera was operated in the flume of the Shasta River Fish Counting Facility (SRFCF) twenty-four hours a day, seven days a week, from September 2, 2020 until January 11, 2021. The first Chinook Salmon was observed on September 5, 2020 and the last Chinook Salmon on December 9, 2020. Klamath River Project (KRP) staff sampled 434 carcasses to collect biological metrics and to determine the presence of Iron Gate Hatchery produced fish.

Chinook Salmon carcasses sampled in the spawning ground surveys (SGS), weir washbacks (WB) and adult trap were used to describe characteristics of the run. We processed 434 carcasses which ranged in fork length (FL) from 39 cm. to 97 cm. Males ranged in FL from 39 cm. to 97 cm. and averaged 61 cm. Females ranged in FL from 45 cm. to 82 cm. and averaged 63 cm. Grilse were determined by scale-based aging. The run was comprised of 393 grilse (9.4%), and 3,775 adults (90.6%). The sex composition of the run, based on 20 SGS fish sampled, was 60% (2,501) female and 40% (1,667) male. No hatchery origin fishes, as denoted by adipose clipped (ad) carcasses, were encountered during SGS sampling, however an estimate of 34 (0.81%) ad fish entered the Shasta River based on video observations. Coded-wire tag (CWT) proportions from Iron Gate Hatchery (IGH) were used to estimate the age classes and release types of IGH Chinook Salmon observed by video in the Shasta River this year.

A net total of 37 Coho Salmon (Oncorhynchus kisutch) were estimated to have entered the Shasta River prior to removal of the weir on January 9, 2020. The first Coho Salmon of the season was observed swimming upstream through the SRFCF on November 14, 2020 and the last Coho Salmon was observed swimming upstream through the SRFCF on January 6, 2021. Seven Coho Salmon carcasses were recovered as WB samples.