Population estimates provided by the California Department of Fish and Wildlife. The Central Valley Chinook Salmon Population Assessment program provides the GrandTab report and CalFish provides the Upper Sacramento River Basin Salmonid Monitoring annual monitoring reports, which present all the detailed data, methodologies, and assumptions. Data for 1963 missing for the 196201969 average. Data are preliminary and subject to change.
Steelhead are federally listed as threatened. The population abundance target shown above for steelhead represents just one of several criteria that the National Marine Fisheries Service considers when determining whether a species should be removed from the Federal List of Endangered and Threatened Wildlife and Plants (50 CFR 223.102). Recovering any of the species entails meeting criteria for abundance, productivity, diversity, and spatial structure across multiple watersheds, as well as criteria for alleviating threats (NMFS, 2014). The population abundance target (i.e., 833) is not specific to Cow Creek; it is a generic, minimum recovery level that applies across the Central Valley Recovery Domain (NMFS, 2014). In-River returns should be primarily, if not exclusively, made up of natural-origin fish in order to support a delisting decision (Lindley et al. 2007).
Fall run Chinook are not listed as endangered or threatened, so there are no recovery targets. An alternative comparison is the Central Valley Project Improvement Act (CVPIA) natural production targets for naturally born fish that return to spawn in the river, including those harvested in the ocean and river prior to spawning. Note the CVPIA goals do not include hatchery returns. This is typically referred to as the CVPIA doubling goal (USFWS, 2001). The CVPIA natural production target for fall run is 4,600. The 2016 natural production estimate is 995 for fall run. US Fish and Wildlife Anadromous Fish Restoration Program
The 2015 snapshot is defined as November 2014 to December 2015, as per when salmon and steelhead return from the ocean to spawn. Late fall run Chinook return in to the Sacramento River and its tributaries in early November through February, with spawning occurring from January through mid-April. Winter run Chinook return as early as December with spawning from April through August. Spring run Chinook return in late January through August, with spawning occurring from mid-August through October. Fall run Chinook return from June through November and spawn from early October through late December. Steelhead migration can start in fall but is primarily during winter and spring, with spawning occurring December through April.
National Marine Fisheries Service. 2014. California Central Valley Salmon & Steelhead Recovery Plan. West Coast Region, Sacramento, California.
US Fish and Wildlife Service. 2001. Final Restoration Plan for the Anadromous Fish Restoration Program. A Plan to Increase Natural Production of Anadromous Fish in the Central Valley of California.
Lindley et al. 2007. Framework for Assessing Viability of Threatened and Endangered Chinook Salmon and Steelhead in the Sacramento-San Joaquin Basin. San Francisco Estuary and Watershed Science 5(1): article 4. February 2007.