During the summer months when stream temperatures rise, Battle Creek supports adult spring-run chinook salmon, as well as the eggs of those fish, once they have spawned. Eggs of the winter run chinook are still incubating in the gravel at the beginning of summer. Salmon eggs are especially sensitive to temperatures. They require colder water than do juveniles and adults, and because they are unable to move out of warm water reaches, they are the most vulnerable when stream temperatures rise. Pre-spawning adults need temperatures below 61 degrees F to insure their vitality.
Warm water can cause infertility and mortality before spawning is achieved.
Adult spring-run chinook arrive in Battle Creek in March through May, and they hold in the stream for several months before they spawn. Chart showing temperature tolerance ranges for different life stages. Several factors influence water temperature in Battle Creek. The upper reaches are naturally cooler because of the elevation. The North Fork flows through a steep canyon, which helps shade the water.