Coho Salmon in a Spring Creek: Life History Tactics in the Shasta River and a Method for Quantifying Movement and Survival

The Shasta River was historically among the top producers of coho salmon in the Klamath system. Its unique spring-dominated hydrology promotes rapid growth rates and provides consistent inter and intra-annual flow. However, surface water diversions degrade the river and its salmonid habitat. A network of approximately twenty PIT tag detection stations have been in operation at key locations throughout the watershed for several years, providing detailed information on habitat use by tagged juvenile coho salmon. During periods of juvenile coho redistribution in early summer, we have documented extensive upstream movements to headwater springs, as well as extensive downstream movements to thermal refugial areas in the mid-Klamath. Some age-0 coho salmon grow to over 100 mm by June when they appear to undergo smoltification and leave the Shasta River. A multi-state mark-recapture modeling framework has been established to estimate seasonal survival and movement parameters in different areas. These analyses have indicated that survival is lowest in summer and as high as 100% in winter. This data has been used to prioritize and evaluate restoration efforts including conservation of cold springs, tailwater reduction, riparian fencing, and coordination among diverters to reduce impacts on coho salmon habitat.