CHINOOK SALMON (SACRAMENTO RIVER WINTER-RUN) 







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Common Name: CHINOOK SALMON 

 Scientific Name: Oncorhynchus tshawytscha 



Listing Date: 11/30/90 



Species Status: Endangered 



Species Trend: Unknown 



Current Estimated Population: Unknown 



Critical Habitat: Designated 



SPECIES POPULATION STATUS 



Winter-run chinook salmon in the Sacramento River, California, are unique and distinguishable 

 from the other three runs of chinook salmon in the river based on the timing of their upstream 

 migration and spawning season. For the most part, the winter-run chinook salmon population is 

 comprised of three year-classes that return to spawn as 3-year-old fish. NMFS determined that 

 the winter-run chinook salmon should be listed as threatened under the ESA because the run has 

 declined more than 97% over a period of less than 20 years. From 1967 through 1969. average 

 run size was about 84,000 fish; in 1982 through 1984, the average was about 2,000 fish. Salmon 

 returns to the river were 550 In 1989, around 450 in 1990, 191 in 1991, 1 180 in 1992, 341 in 

 1993. 189 in 1994. and 1,361 in 1995. 



The winter-run chinook has declined in the Sacramento River primarily due to water 

 management projects which have modified the river and taken away spawning habitat in the 

 upper Sacramento River. Water deliveries for agriculture in early summer deplete the storage of 

 cold water in Shasta Reservoir and raise the temperature to a level that is lethal to salmon eggs. 

 Winter-run chinook spawn from mid April to mid August with a peak in May and June. The eggs 

 incubate and hatch in about 2 months. If the water temperature is too high (especially during the 

 peak incubation and hatching months of July through September), the eggs do not hatch. 

 Juveniles migrate to the sea from August into the spring months. Water diversions and other 

 water management actions such as inadequate fish screens at diversion facilities can be lethal to 

 migrating juveniles. Adult fish begin returning from the sea during the winter. While at sea, they 

 may be taken incidentally to commercial and recreational fishing for other species of salmon. 



On January 4, 1994, NMFS issued a determination that the Sacramento River winter-run chinook 

 salmon should be reclassified from threatened to endangered. This determination was based on 

 the continued decline and increased variability of run sizes since its first listing as threatened in 

 1989, the expectation of weak returns in certain years as the result of two small year classes 

 (1993 and 1994) and continuing threats to the population. 



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