The Trinity River Division of the Central Valley Project in California included construction of Trinity and Lewiston dams that divert a substantial portion of the river's flow to the Central Valley for agricultural, municipal and industrial uses. Lewiston Dam, completed in 1963, is the upstream limit of anadromy, blocking access to 109 miles of salmon and trout spawning and rearing habitat. Trinity River Hatchery (TRH) was constructed at river mile 110 at the base of Lewiston Dam to mitigate for the loss of this anadromous fish habitat. The Bureau of Reclamation funds operation and maintenance of the TRH, which is operated and managed by the CDFG.
Mitigation goals for lost adult production were determined from pre‐project studies of anadromous fish populations in the basin. The USFWS and CDFG (1956) estimated that 5,000 coho; 3,000 spring Chinook, 8,000 summer Chinook and 24,000 fall Chinook; and 10,000 steelhead (no run timing was designated) passed above the Lewiston Dam site prior to its construction. Total annual adult production goals (catch plus escapement) for TRH were further defined in 1980 to be 7,500 coho, 6,000 spring Chinook, 70,000 fall Chinook and 22,000 steelhead (Frederickson et al. 1980). Escapement goals to the hatchery were further defined in 1983 as 2,100 coho, 3,000 spring Chinook, 9,000 fall Chinook and 10,000 steelhead (USFWS 1983).
The Southern Oregon / Northern California Coasts coho salmon ESU was classified under the ESA as threatened in 1997. The ESU includes all naturally spawned populations of coho salmon in coastal streams between Cape Blanco, Oregon, and Punta Gorda, California, and the Iron Gate Hatchery, Trinity River Hatchery, and Cole River Hatchery coho programs.
Text from: California Hatchery Review Statewide Report - 2012