smoltification in steelhead.

Juvenile steelhead may remain in the river for one to three years before smolting and migrating to sea. Individual steelhead populations leave the ocean and migrate into their freshwater spawning tributaries at different times of the year. Two general forms exist--"summer-run steelhead" and "winter-run steelhead". Summer-run fish leave the ocean between May and October before their reproductive organs are fully mature. They mature in freshwater while en route to spawning