Freshwater rearing strategies of spring Chinook salmon (Oncorhynchus tshawytscha) in Salmon River tributaries, Klamath Basin, California

The freshwater life history of spring chinook salmon Oncorhynchus tschawytscha was investigated in the upper South Fork Salmon River and its tributary East Fork. Emergence and emigration timing were studied using redd and outmigrant traps during 1991 and freshwater residency evaluated through analysis of adult and juvenile scales collected between 1990 -1994. For the 10 redds monitored, egg and alevin incubation averaged 203 days with emergence extending into late May. Emigration pulses from natal tributaries were observed in spring, early summer, and fall. Analysis of scales indicated the majority of spring chinook returning to spawn exhibited freshwater rearing through fall, corresponding with the observed fall 1991 emigration pulse. This suggests the upper South Fork Salmon River watershed is utilized by juvenile spring chinook for extended freshwater rearing and this strategy is necessary for reproductive success. Maintenance and rehabilitation of freshwater habitat conditions in the Salmon, Shasta, Scott, and mainstem Klamath Rivers which provide extended rearing could be critical to restoration of spring chinook salmon.