Effects of temperature, flow, and disturbance on adult spring-run chinook salmon
Spring-run chinook salmon (Oncorhynchus tshawytscha) have an unusual life history pattern in that they move into their spawning streams in the spring, hold there all summer in deep pools, and then spawn in the fall. Populations in the Sacramento-San Joaquin and Klamath-Trinity drainages have declined dramatically in recent years perhaps due to their exceptional vulnerability to the negative effects of water diversions (e.g. low flows/high temperatures) and human disturbances in their stream habitat. We examined the limits of pool holding capacity under varying conditions of temperature, flow, and human use primarily in a 2.3 km study stretch in the upper reaches of Deer Creek (Tehama County) during 1991.
We found some evidence that spring-run chinook salmon continually move upstream over the summer. However, pool depth also affected the presence of adult salmon. The number of salmon counted reached an asymptote in many pools over the summer, suggesting that pools have a limited holding capacity. Human rafting activity caused an increase in salmon movement in pools, and may stress salmon if it is a common activity. We documented substantial evidence of possible harassment and poaching of salmon in a 2.3 km study stretch of Deer Creek during 1991. This evidence included the presence of heavy line and treble hooks in pools containing adult salmon, and we even observed people with snorkeling equipment trying to capture adult salmon with a dipnet. Estimated spawning success was about 50-60% in Butte Creek in 1989 and Deer Creek in 1990 and 1991.