The coastal cutthroat troutOncorhynchus clarki clarkioccurs along the Pacific coast of North America from Humboldt Bay, California, to Prince William Sound, Alaska, in a zone that closely overlaps the coastal rain forest belt. This species exhibits anadromous, potamodromous stream-dwelling, potamodromous lake-dwelling, and headwater stream-resident life history forms. Anadromous fish spawn in small tributaries from late winter through spring, depending on the locality. Juveniles remain in streams for two or more years and congregate during their early months in habitats along stream edges. Later, they move to pools unless coho salmonO. kisutchare present, in which case they are driven to riffles. Most anadromous cutthroat trout juveniles smolt at age 2 if they migrate to sheltered saltwater areas or age 3 or 4 if they migrate to the open ocean. Seaward migration peaks in May, and the fish remain close inshore while in salt water. The fish seldom overwinter at sea but return to rivers in the fall or winter of the year they go to sea. In some instances, these are overwintering migrations only, because anadromous female cutthroat trout seldom spawn before age 4. Potamodromous forms migrate to main-stem rivers or to lakes; otherwise, their life history characteristics are much like those of the anadromous form. Headwater stream-resident cutthroat trout become sexually mature as early as age 2, but seldom live beyond age 4 or 5. These fish exhibit only limited instream movements and generally live out their lives within 200 m of their birthplace.