Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and North America. Like other sea-run (anadromous) trout and salmon, steelhead spawn in freshwater, smolts migrate to the ocean to forage for several years and adults return to their natal streams to spawn. Steelhead are iteroparous, although survival is approximately 10–20%. Description The freshwater form of the steelhead is the rainbow trout (Oncorhynchus mykiss). The difference between these forms of the species is that steelhead migrate to the ocean and return to freshwater tributaries to spawn, whereas non-anadromous rainbow trout do not leave freshwater. Steelhead are also larger and less colorful than rainbow trout, and can weigh up to and reach in length. They can live up to 11 years and spawn multiple times. The body of the steelhead trout is silvery and streamlined with a rounder head. There are black dots and a red or pink stripe running horizontally down the sides of the fish. This silver color and round head is what gives the steelhead its name. A number of distinct population segments of steelhead are endangered or threatened across the United States, mostly caused by the blocking of waterways by the construction of dams. Human interaction has had considerable consequences on reducing the population of steelhead trout. Characteristics Steelhead currently support or have historically supported fisheries across Northern California, and thus they hold "economic as well as cultural value" (Moyle, Israel, & Purdy, 2008). Contrary to popular belief, the California Steelhead is a coastal variation of the same species of fish as the Rainbow Trout, Oncorhynchus mykiss; "rainbow trout are the 'landlocked' version, and remain in freshwater throughout their life" (King County, 2016). An ocean-going variety, the Steelhead, or Oncorhynchus mykiss irideus has developed unique adaptive characteristics that distinguish this fish from its common counterpart and have allowed a wider distribution of this species across the Pacific Northwest, including the coastal regions of California. In fact, "coastal rainbow trout is the most widely-distributed native trout form" (CA.gov). Among other necessary biological utilities fulfilled by this species, Steelhead Trout "are also strong indicators of the condition of California’s streams; large self-sustaining populations of native salmon and trout are found where streams are in reasonably good condition" (Moyle, Israel, & Purdy, 2008).