Juvenile Fall Chinook rear for several months and begin migration downstream to the ocean during June through August of the same year as fry emergence. After spending one to two years in the ocean, adults migrate into the Columbia and Snake rivers from July through October. Adults enter the Grande Ronde and Imnaha rivers from late summer to early spring. Adults hold through the winter and begin to migrate upstream again as water temperatures and flows increase during February and March. Spawning occurs in smaller tributaries from late March through early June.
Eggs incubate in the gravel for one to two months depending on water temperature.
Fry emerge in June and early July. Juvenile Summer Steelhead rear in county streams for up to three years, with most leaving after two years. Smolts migrate downstream to the ocean on high flows from April through June. Resident Rainbow Trout Rainbow generally mature after three years. Spawning occurs in smaller tributaries from late March through early June.