Success in a Hatchery Program with Fall Chinook Salmon by Simulating the Natural Life History of the Stock

Life histories of juvenile fall chinook salmon (Oncorhynchus tshawytscha) vary among and within stocks. In Elk River on the southern coast of Oregon, most juveniles live in fresh water for 6 to 7 months, grow to a large size, and migrate to sea in autumn. When this life history was simulated in the rearing program at Elk River Hatchery for the 1968, 1969, and 1970 broods, esimates of survival back to the river of five different hatchery releases averaged 4.3% and ranged from 3.3 to 5.8%. A release of 1968-brood fish reared until they were yearlings had a survival of 2.2%. However, when fish from the 1970 brood were reared in the hatchery for only a short period and released in early summer, as in a more traditional hatchery rearing program for fall chinook salmon, survival to return was only 0.3%. These results suggest that simulating the natural life history of native stocks in hatchery programs can have substantial benefit.