Quick facts

Common names: brown trout, sea trout

Scientific name: Salmo trutta

Family: Salmonidae

Habitat: lakes, rivers, streams and salt water

Diet: small fish, insect larvae, crustaceans, flying insects

Predators: mink, otter, cormorants, pike

Origin: native

What do brown trout look like?

The brown trout is, as the name suggests, brown in colour. It varies from light silvery brown to the more common golden brown hue, and has darker spots on its back and sides, with a pale belly.

It is medium to large in size, measuring in at around 40-80cm and weighing up to 15kg.

Brown trout close-up

Credit: Linda Pitkin / naturepl.com

What do brown trout eat?

These fish are keen predators, enjoying a diet of land and water invertebrates and larvae, crustaceans and small fish. Larger trout will sometimes even eat small swimming mammals, like voles and mice.

Did you know?

Brown trout can live for up to 20 years.

How do brown trout breed?

The spawning season for brown trout occurs at the beginning of the year, from January to March. Females will make an impression on the gravelly river bed, which will form the nest. Once the nest is built, the male trout will defend it until the female is ready to lay the eggs. The male will then fertilise the eggs as they are being laid, before they are buried in gravel.

The young, known as ‘fry’, then hatch, and for the first month they lack any scales. They feed on the yolk sac to begin with, until they are ready to feed on invertebrates.

Brown trout jumping to catch insect

Credit: Andy Rouse / naturepl.com

Where to find brown trout

The brown trout is a widespread species found throughout the UK. It lives in streams, rivers, lakes and salt water habitats. Brown trout and sea trout are actually the same species. Brown trout spend all of their time in freshwater habitats, while sea trout live in the sea. Sea trout migrate to fresh water to spawn.

Signs and spotting tips

Keep an eye out for brown trout in rivers and streams – if you’re lucky you might spot one jumping out of the water in search of insects.

Threats and conservation

The brown trout is not believed to be endangered, however it is threatened by overfishing, habitat loss and climate change. Climate change in particular is a big issue for this species, as it relies on coldwater habitats to survive.

Did you know?

A trout can see out of both corners of each eye simultaneously – meaning it can see in almost every direction at once.