The principal late-fall-run Chinook migration into the Sacramento River occurs during mid-October through mid-April. Spawning occurs from January through mid-April and egg
incubation occurs from January through June. The principal spawning habitat for late-fall-run Chinook is found in the upper Sacramento River in river reaches downstream from Keswick Dam. Rearing and downstream migration or dispersal of juvenile fish from upstream to downstream areas can occur from April through December. The primary movement of smolts through the Delta is believed to occur during the winter months.