Columbia River Research Laboratory
Chinook salmon (Oncorhynchus tshawytscha)
Chinook salmon is the largest of the Pacific salmon species and adults can exceed 40 pounds. The species exhibits a variety of juvenile life history types, and young fish can spend anywhere from 3 months to 2 years in a diverse range of freshwater habitats before migrating to the sea to begin their marine existence. Chinook salmon remain at sea for 1 to 6 years (more commonly 2 to 4 years) before returning to fresh water to spawn. Chinook salmon are divided into “runs” (i.e., spring, summer, fall, or winter) depending on the time of year fish return to spawn, and single rivers may support multiple runs. Returning adults are powerful swimmers and some populations swim upstream hundreds of miles to reach their spawning grounds. A female Chinook salmon digs a spawning nest called a redd in which she and a courting male deposit eggs and milt. Chinook salmon are semelparous and die after they spawn. There are numerous Chinook salmon stocks in the Columbia River basin that are currently listed under the Endangered Species Act, but the fall Chinook salmon that spawn in the Hanford Reach of the Columbia River is considered one of the few healthy stocks.