Rainbow trout

Oncorhynchus mykiss

Rainbow trout are native to watersheds west of the Cascade Mountains. They have been introduced elsewhere in North America and on every continent except Antarctica for food and sport fishing. They are omnivores.

Rainbow trout are in the salmon family. The "rainbow" refers to a reddish-pink stripe on the fish's side. Onchorynchus means "hooked nose" referring to the hooklike lower jaw (called a kype) males develop during spawning season.

Rainbow trout behavior and facts

  • Cold headwaters, creeks, rivers, cool lakes, estuaries and oceans are habitats used by different populations of Oncorynchus mykiss. Those fish that spend their entire lives in freshwater are called rainbow trout.
  • Some populations of Oncorhynchus mykiss are called steelhead trout. Though they are the same species, they are anadromous (born in freshwater, migrate to the sea in adulthood and return to freshwater to spawn).
  • Unlike other salmon species, rainbow trout can spawn more than once.
  • Rainbow trout eat aquatic and terrestrial insects, mollusks, crustaceans, fish eggs, minnows and other small fish (including other trout).

From birth to death

  • Trout spawn in main river channels and tributaries, and inlet and outlet streams of lakes. Using her tail, the female digs a depression called a redd in gravel. She deposits eggs in the redd and the male fertilizes them. The eggs are then covered with gravel and she digs another redd upstream.
  • Fry emerge a few weeks later.
  • Sexual maturity: 2 to 3 years
  • Lifespan: up to 11 years
  • Vital statistics
  • Length: 27.5 inches or longer, up to 45 inches
  • Weight: Up to 55 pounds, but usually much smaller


Rainbow trout are listed as not threatened.

Rainbow trout, the Oregon Zoo and you

You can see rainbow trout at the zoo's Eagle Canyon exhibit. They are fed trout chow and insects. Rainbow trout and other fish in the salmon family require clear, silt-free waters for spawning.

Building dams, filling in wetlands and straightening rivers' courses are all human activities that alter river habitats and can negatively affect trout and other species.