CHINOOK SALMON (SNAKE RIVER SPRING/SUMMER) 





Common Name: CHINOOK SALMON 

 Scientific Name: Oncorhynchus ishcmytscha 



Listing Date: 04/22/92 



Species Status: Threatened 



Species Trend: Unknown 



Current Estimated Population: See Species Population Status 



Critical Habitat: Designated 



SPECIES POPULATION STATUS 



Production in the Snake River probably exceeded 1.5 million spring/summer chinook salmon for 

 some years during the late 1800's. By the early-1900's, production severely declined. An estimate 

 of the average number of adults returning from 1950 to 1960 is 125.000. Using an expansion 

 factor method (adult counts vs. number of redds), the estimated number of adult wild fish at 

 Lower Granite Dam averaged 8,731 from 1980 to 1990 (low of 5.379 in 1989, high of 1 1,269 in 

 1981). Estimated naturallv-produced fish returns were 5,020 in 1991, 12,433 in 1992, 9,967 in 

 1993, 1,721 in 1994, 1,116 in 1995. and 3,487 in 1996. Aduh returns in 1994 and 1995 were 

 record lows, as a result of drought and poor ocean conditions related to the 1992-1993 El Nino. 

 Returns are expected to have improved somewhat in 1996 and improve substantially in 1997 and 

 1998. 



SPECIES BIOLOGY 



The chinook salmon is noted for the black spotting on its back, dorsal fin. and both caudal fin 

 lobes, black pigment along the bases of the teeth and loose conical teeth in mature individuals. 

 Salmon over 14 kg are likely to be chinook. 



Snake River spring/summer chinook use small, higher elevation streams for spawning and early 

 juvenile rearing. They migrate to sea as yearling smolts (stream-type). Detailed life history data 

 are limited for wild populations. Age at spawning and associated fecundity differ between the 

 adults returning to the Middle Fork and main Salmon Rivers and all other areas for which 

 information is available. In these two areas, 3-ocean adults (salmon that spend three years 

 maturing in the ocean) with higher fecundity predominate, whereas 2-ocean adults (salmon that 

 spend two years maturing in the ocean) with lower fecundity predominate in other areas. Adult 

 spring chinook enter the Columbia River in spring, as early as Februar>-, reach the Snake River 

 by late April, arrive in natal tributaries in May and June, hold in deep pools, and spawn in late 

 August. Adult summer chinook reach the Snake River in June and July, arrive in natal tributaries 

 by early July, and spawn in early September. 



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