Bony fish · Salmoniformes · Salmonidae

Rainbow Trout

Oncorhynchus mykiss

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

It has two entirely different ways of life within the same species: the resident freshwater rainbow trout and the anadromous 'steelhead', which migrates to the ocean before returning to spawn in its home river.

Weight

450 g – 25.9 kg

Size

up to 1.2 m

Lifespan

6 years

Diet

Carnivore

Feeds mainly on other animals.

Activity

Irregular activity

Active at irregular times, by day or night depending on circumstances.

Social structure

Solitary

Lives and hunts alone, joining others only to breed.

Sighting difficulty

Easy

OceanFreshwaterCarnivore Variable activity Solitary Fish Ocean Freshwater

73countries 4parks 9dive sites9same family

Fun facts

The steelhead shows a remarkable instinct for returning to its birthplace after 2 to 3 years at sea.
It eats insects, crustaceans, molluscs and small fish.
It has been widely introduced around the world for aquaculture and sport fishing.

Life cycle & biology

Skeleton type: Vertebrate - internal bony skeleton (fish)
Habitat & environment: Cold rivers and streams of the Pacific coast of North America (native form); widely introduced worldwide for aquaculture and sport fishing
Birth weight: A larva (fry) on hatching from the egg
Size at birth: Tiny at hatching
Sexual maturity: 1-3 years (usual reference 2-3 years)
Gestation / incubation: 3-12 weeks (30-100 days depending on temperature)
Litter / clutch size: 500 to 9,000 eggs per female

Sources consulted: Illinois DNR; FishBase; Maryland DNR; MDB Fish Fact Sheet; Animal Diversity Web; U.S. Fish and Wildlife Service; DOAJ

Where to find it

See its range on the interactive map

Best time: From winter to spring in its native range in the North American Pacific, during spawning; in Europe it is introduced in rivers and fish farms.