Rainbow trout

Rainbow Trout

Rainbow Trout ©Alex Mustard/2020VISION

Rainbow trout

Scientific name: Oncorhynchus mykiss
With a silvery body, and purple, pink and bluish streaks down its flanks, the rainbow trout lives up to its name. Popular with anglers, it is actually an introduced species in the UK.

Species information


Length: 50-70cm
Weight: up to 14kg
Average Lifespan: 4-6 years

Conservation status

Introduced species.

When to see

January to December


A large fish, the rainbow trout was introduced into UK fish farms from North America in the early 20th century; it has now become established in rivers and lakes throughout the country. It can live in poorer quality water than our native brown trout or Atlantic salmon. A predatory fish, it feeds on insect larvae, small fish and flying insects, such as mayflies and damselflies.

How to identify

A silvery-brown, dark-spotted fish, the rainbow trout can be distinguished from the similar brown trout by the broad, purple stripe that runs along its flanks.



Did you know?

The rainbow trout has been introduced to every continent except Antarctica. As well as a freshwater race, there is also a migratory race - the Steelhead - which lives at sea and moves up-river to spawn.

How people can help

The Wildlife Trusts work with researchers, scientists and other conservationists to monitor changes in our wildlife to determine the effects of environmental change, such as the introduction of a new species or climate change. You can help by supporting your local Trust and becoming a member; you'll find out about exciting wildlife news, events on your doorstep and volunteering opportunities, and will be helping local wildlife along the way.