Rainbow Trout

Onchorynchus mykiss

  1. Wildlife
  2. Freshwater fish
  3. Rainbow Trout


A large fish, the rainbow trout was introduced into fish farms in the UK from North America in the early 20th century and 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 running down its flanks.

Where to find it

Found throughout the country.


When to find it

  • January
  • February
  • March
  • April
  • May
  • June
  • July
  • August
  • September
  • October
  • November
  • December

How can people help

An introduced species, the rainbow trout is economically important and popular with anglers because of its fast growing rate and ability to live in more polluted river systems. The Wildlife Trusts work with researchers, scientists and other conservationists to monitor changes in our native wildlife to determine the effects of environmental change, such as the introduction of new species or climate change. You can help by supporting your local Trust and becoming a member; you'll find out about exciting wildlife happenings, events on your doorstep and volunteering opportunities, and be helping local wildlife along the way.

Species information

Common name
Rainbow Trout
Latin name
Onchorynchus mykiss
Freshwater fish
Length: 50-70cm Weight: up to 3.5kg Average Lifespan: 4-6 years
Conservation status
Introduced species.