Redding, CA (2023) – Current monitoring methods and data are inadequate in providing sufficient insight into the status and success of winter-run Chinook salmon in the upper Sacramento River. To address this problem, a new study has been conducted to better understand how genetic testing and methodology can add value to existing winter-run Chinook salmon monitoring data.

The primary sources of winter-run population information are the annual estimation of spawning adults present and the annual estimate of fry-equivalents passing Red Bluff Diversion Dam. While these estimates are useful for documenting the status of each annual cohort, they are not designed to detect biological responses to environmental variation and management actions.

The new study uses genetic testing to enable the estimation of productivity rates, variation in productivity within the population (hatchery vs. wild), population viability, successful reproduction (recruitment), and egg-to-fry survival. The study requires a representative sample of adults and juveniles. Adult samples were obtained from the winter run Chinook Salmon adult carcass survey, collected by the California Department of Fish and Wildlife (CDFW). Juvenile samples were obtained from outmigrants captured within rotary screw traps at Red Bluff Diversion Dam, collected by the US Fish and Wildlife Service (USFWS).

Genotype data from individual samples were generated using GTSeq high throughput sequencing and analyzed using parentage and relatedness methods. In addition, statistical analyses were performed on genetic data products. The study aims to improve the estimate of spawning adults, egg-to-fry survival calculations, variation in productivity within the population (hatchery vs. wild), population viability, and factors associated with successful reproduction (recruitment).

This genetic study provides a means for evaluation of recruitment patterns, viability, and successful reproduction of natural- and hatchery-origin fish, and will aid in understanding the factors that influence variability in observed winter-run Chinook salmon abundance and productivity.

The study was conducted by a team at Cramer Fish Sciences – Genidaqs, in partnership with various organizations, including the U.S. Bureau of Reclamation, Sacramento River Settlement Contractors, California Department of Fish and Wildlife, U.S. Fish and Wildlife Service, and others. The study results will be shared with various interested parties, including resource managers and decision-makers, to aid in the conservation and management of winter-run Chinook salmon in the upper Sacramento River.

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