Rainbow trout fishery and spawning stock in the Upper Klamath River Wild Trout Area, Copco, California

The rainbow trout fishery in the Upper Klamath River Wild Trout Area was examined in 1981 and 1982. In the spring of 1982, 281 mature rainbow trout were trapped at the mouth of Shovel Creek, the only known spawning tributary to the area. Males were 78 percent age two and females were 89 percent age three. Less than 10 percent of the upstream migrants had scale checks indicating prior spawning and less than 10 percent were recaptured as spent downstream migrants. Spawning success could have been limited by a lack of suitable spawning gravel, dewatering of redds from irrigation diversions, and fine sediments in the redds (13 percent of redd volume less than 0.85 millimeters in diameter) possibly from logging and cattle grazing in the area. The 1982 spawning produced a year class estimated to contribute a maximum of 32,903 fish to the Upper Klamath River. Most emigrated at age 0, and the few older fish rearing in Shovel Creek had slower growth than spawners or creeled fish. Rainbow trout creeled in the Upper Klamath River Wild Trout Area were primarily age one and two, with yearlings entering the fishery in late July. Creeled fish were significantly larger than spawners at back-calculated ages one (p < 0. 05) and two (p <0.01). Catch averaged 0.5 rainbow trout per hour; average fork length was 240 millimeters. Juvenile steelhead stoced in Copco Reservoir (31,000 to 100,312 yearly in 1978 to 1980) possibly contributed to the Upper Klamath River Wild Trout Area creel and/or the Shovel Creek spawning run.