The coastal cutthroat trout (Oncorhynchus clarkii clarkii) also known as the sea run cutthroat, or harvest trout are a subspecies of cutthroat trout with an anadromous life history.
Adults migrate from the ocean to spawn in fresh water. Juveniles migrate to the sea where they feed and become sexually mature before returning to fresh water to overwinter and spawn. Unlike steelhead and other Pacific salmon, coastal cutthroat do not make lengthy migrations out to sea. Generally speaking, coastal cutthroat will remain in or near estuarine waters, usually within 5–10 mi (10–15km) of their natal stream. Some cutthroat, however, have been shown to move as far as 70 mi (110 km) into the open ocean. There are also lacustrine and riverine populations that spend their entire lives in freshwater. One such population is the trout of Lake Crescent in Washington state that was formerly considered to be a separate subspecies called the Crescenti trout, Oncorhynchus clarkii crescenti.
While some runs of coastal cutthroat are currently endangered, mainly in the southern part of the range, O. c. clarkii has fared better than some of the other subspecies.