The California Department of Fish and Game's Trinity River Project conducted tag and recapture operations from May through December 1990 to obtain chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), and fall-run steelhead (O. mykiss) run-size, in-river harvest, and spawner escapement estimates in the Trinity River basin. We placed weirs in the Trinity River near the towns of Junction City and Willow Creek, and trapped 1,160 spring-run and 1,144 fall-run chinook salmon, 431 coho salmon, and 463 fall-run steelhead.
Based on tagged fish recovered at Trinity River Hatchery and on the return of reward tags by anglers, we estimate 6,388 spring-run chinook salmon migrated into the Trinity River basin upstream of Junction City Weir and that 845 (13.2%) were caught by anglers, leaving 5,543 fish as potential spawners. We estimate 9,992 fall-run chinook salmon migrated past Willow Creek Weir and that 4,787 of these fish continued up the Trinity River past Junction City Weir. Anglers harvested an estimated 350 (3.5%) of the fall-run chinook salmon that passed Willow Creek Weir, leaving 9,642 fish as potential spawners.
The coho salmon run in the Trinity River basin upstream of Willow Creek Weir was 3,897 fish, of which 2,177 continued their migration past Junction City Weir. Anglers harvested an estimated 47 (1.2%) of the coho salmon that migrated past Willow Creek Weir, leaving 3,850 fish as potential spawners.
An estimated 5,348 adult fall-run steelhead entered the Trinity River basin upstream of Willow Creek Weir, and 3,296 continued their migration upstream of Junction City Weir. Anglers harvested 1,230 (23.0%) of the adult fall-run steelhead that migrated past Willow Creek Weir, leaving 4,118 fish as potential spawners.
1. To determine the size, composition, distribution and timing of adult chinook and coho salmon, and steelhead runs in the Trinity River basin.
2. To determine the angler harvest and spawner escapements of Trinity River chinook and coho salmon, and steelhead.
The California Department of Fish and Game's (CDFG) Trinity River Project (TRP) conducts annual tagging and recapture operations for adult chinook and coho salmon, and fall-run steelhead in the mainstem Trinity River. This effort determines the composition (species, race, and proportion of hatchery-marked or Project-tagged fish), distribution, and timing of the chinook and coho salmon, and fall steelhead runs in the Trinity River basin. Recaptures of hatchery-marked and Project-tagged fish are used to develop run-size, angler harvest, and spawner escapement estimates for each chinook and coho salmon, and steelhead run.
This is a continuation of studies that began in 1977 with the trapping, tagging, and recapture of fall-run chinook salmon (fall chinook), coho salmon (coho), and fall-run steelhead (steelhead) in the Trinity River in order to determine run-size and angler harvest rates. In 1978, similar studies were added to include spring-run chinook salmon (spring chinook). Steelhead were dropped from the program in 1985 through 1989 and reinstated this year (fall 1990).
The earlier studies were funded by the U.S. Bureau of Reclamation (U.S.B.R.) and Anadromous Fish Act funds administered by the U.S. Fish and Wildlife Service and National Marine Fisheries Service. The U.S.B.R. (PL 98-541) has funded the program from 1 October 1989 through the present.
Prior to the current program, all efforts to measure salmon and steelhead populations in the Trinity River basin had been restricted to portions of the upper main stem Trinity River and certain of its tributaries, or the South Fork Trinity River and some of its tributaries (Gibbs 1956; La Faunce 1965a, 1965b, 1967; Miller 1975; Moffett and Smith 1950; Rogers 1970, 1972, 1973a, 1973b, 1982; Smith 1975; Weber 1965). These earlier efforts did not include fish which use the main stem and tributaries of the lower Trinity River, or attempt to determine the proportion of hatchery fish in the runs and the rates at which various runs contribute to the fisheries. To develop a comprehensive management plan for the Trinity River basin, all salmon stocks utilizing the basin must be considered.
