GrandTab. California Central Valley Chinook Escapement Database Report
California Department of Fish and Wildlife, Fisheries Branch
California Central Valley, Sacramento and San Joaquin River Systems
Chinook Salmon Escapement, Hatcheries and Natural Areas
The Sacramento-San Joaquin River system in California's Central Valley is the principal producer of Chinook Salmon (Oncorhynchus tshawytscha) caught in California's ocean fisheries and contributes appreciably to Chinook Salmon harvest off the coasts of Oregon and Washington. This system also supports one of the largest river sport fisheries for Chinook Salmon on the Pacific Coast in the Sacramento River.
Chinook Salmon in the Central Valley are comprised of four runs (late-fall, winter, spring, and fall) named for the season when most of the run enters freshwater as adults. Late-fall run arrive in the upper Sacramento River and its tributaries in September through February and spawn from December through mid-April. Winter-run spawns almost entirely in the upper Sacramento River and its tributaries upstream of Red Bluff, arriving as early as December, and spawning from April through August. Spring-run salmon return from the ocean in late January through August; early arrivals oversummer in stream holding pools and spawn from mid-August through October. Fall run salmon return from the ocean from June through November and spawn from early October through January.
California Department of Fish and Wildlife (CDFW) and partners conduct escapement surveys for Central Valley Chinook Salmon annually. The surveys cover the major natural spawning areas, and many minor ones, throughout the Sacramento-San Joaquin River system. Estimates are made using a variety of methods, depending upon the setting, conditions, and resources for making the most accurate estimate. Methods include mark-recapture carcass surveys, video counts at dams and in small tributaries, direct observation counts both on-ground and by snorkeling, and expanded redd counts conducted from the ground and the air. Counts are also made at all five anadromous hatcheries and rearing facilities in the Central Valley. Partners providing estimates and counts include CDFW, U.S. Fish and Wildlife Service, Pacific States Marine Fisheries Commission, California Department of Water Resources, East Bay Municipal Utilities District, Lower Yuba River Management Team, and the Fishery Foundation of California.
CDFW compiles annual escapement estimates and counts in the GrandTab database report. GrandTab includes estimates for all four Central Valley runs of Chinook Salmon. The estimates are organized by major basin (Sacramento and San Joaquin) and then sub-basin (tributary streams and rivers) with natural spawning areas and hatcheries represented. The numbers for each run are also totaled by major basin and for the Central Valley as a whole.
Estimates of escapement in GrandTab represent the number of adult Chinook Salmon that escaped the ocean and successfully migrated upstream to a natural spawning area or hatchery. While escapement estimates represent the number of adult salmon available for spawning, these numbers may not represent the number of salmon that succeed in spawning. Pre-spawning mortality can result in a notable difference in the escapement estimate and actual spawners. While pre-spawning mortality occurs in all runs to varying degrees and is often a small proportion of the total escapement, adverse conditions may exacerbate levels of pre-spawning mortality.
Central Valley spring-run Chinook Salmon are particularly susceptible to high levels of pre-spawning mortality, especially under drought conditions, because of their protracted summer holding period in natural spawning areas prior to spawning during late summer-early fall. As a result, the escapement estimates in GrandTab may not represent the number of adult salmon that actually spawned in each stream or river. This may be an important consideration when using GrandTab data for investigating Central Valley Chinook Salmon stock-recruitment relationships, for developing production models, or for assessing spawning habitat quality. Where available, spawner estimates are shown alongside escapement estimates for spring run. These are shown for comparison, and are not included in totals, as they are a subset of escapement. When uncertain, users of GrandTab data are advised to consult the full escapement report for a given escapement estimate.
Thanks to Dick Painter and Bob Kano (CDFW retired) for designing and maintaining GrandTab in its earlier forms. Thanks to Dr. Rob Titus and Tracy Grimes (CDFW) for writing and editing the introduction. Thanks to the cooperating partners that provide escapement estimates and counts in support of GrandTab.
Azat, J. and Killam, D. GrandTab California Central Valley Chinook Escapement Database Report. California Department of Fish and Wildlife
GrandTab is currently available for download here:
https://www.wildlife.ca.gov/Conservation/Fishes/Chinook-Salmon/Anadromous-Assessment
http://www.calfish.org/ProgramsData/Species/CDFWAnadromousResourceAssessment.aspx