Rainbow Trout

By Alex Clayton · Updated 23 October 2026

The rainbow trout (Oncorhynchus mykiss) is a North American fish, first shipped to Britain as hatchery stock in 1884-85. It is not native here. The brown trout is the only trout that is.

It is still the trout most anglers meet first on a stillwater, and almost every rainbow trout UK fisheries hold was put there. Stocked fish are mostly infertile or all-female, and the Wild Trout Trust names only one UK river, the Derbyshire Wye, as holding a self-sustaining population.

That one fact explains where you find rainbows, when you can fish for them and why the British record is so confusing. This guide covers identification, stocking, blue trout, seasons and licences, methods and the record. For the other game species, see our game fish species guides.

Rainbow Trout at a Glance

The core facts, with the sources below the table.

Fact	Detail
Scientific name	Oncorhynchus mykiss
Native range	Pacific coast of North America
UK status	Non-native. First shipped 1884-85, first UK records around 1907-1910
Adult length	Typically 50-70 cm
Maximum weight	Up to about 31lb (14 kg)
Lifespan	About 4-6 years
Breeding in the UK	Rare. Stocked fish are mostly infertile or all-female
Where found	Stocked stillwaters and reservoirs. The Derbyshire Wye is the only named self-sustaining river population
Water tolerance	Copes with warmer and poorer-quality water than brown trout or salmon

Sources: the Wild Trout Trust and the Wildlife Trusts, with the Canal & River Trust agreeing on lifespan.

The size and weight figures describe the species worldwide. The British record is a separate question, covered in the record section further down.

How to Identify a Rainbow Trout (and Not Mistake It for a Brown)

Two checks settle it: look at the spots, then look along the flank.

A rainbow trout carries black spots only. A brown trout carries black spots too, but mixed with red and orange ones, according to the Wild Trout Trust.

The second check is the band. Rainbows show a pink or red lateral stripe along the side, which is where the name comes from. If the band is hard to make out, go back to the spots, because they are the more reliable of the two checks.

The Canal & River Trust adds two finer details. It describes the rainbow’s tail fin as black-spotted on a pale background, and gives a lateral line scale count of 135-150. Treat these as supporting clues, not rules.

Feature	Rainbow trout	Brown trout
Spot colours	Black only	Black, red and orange
Flank	Pink or red lateral band	No pink band
Tail	Black spots on a pale background (CRT)	See the brown trout guide
Origin	North America, stocked	Native to the UK

A sea trout is a sea-going brown trout, so it follows brown trout spotting rather than rainbow spotting. The cutthroat trout, a North American relative the Wild Trout Trust also describes, has a red or orange slash along the lower jaw.

Blue and golden variants change the overall colour, so trust the spots and band over general appearance. For lookalikes across all species, see our UK fish identification guide.

Black spots only and a pink band means rainbow; any red or orange spots means brown.

Why Nearly Every UK Rainbow Trout Is Stocked

Rainbows have been in Britain since the 1880s, so why have they not spread through UK rivers?

Because fisheries put them there and use fish that cannot breed. Hatchery fish were first shipped from the USA in 1884-85, with the first UK records around 1907-1910, according to the Wild Trout Trust.

Fisheries use stocked rainbow trout because they tolerate warmer water than brown trout. That makes them easier to keep in small lowland lakes through a hot summer.

Then there is sterility. Rainbows farmed for food or for stocking are infertile or all-female. Infertile fish are usually triploid: they carry an extra set of chromosomes that stops them breeding. The Wild Trout Trust notes that occasional parr and spawning attempts are still seen, possibly because producing sterile triploids is not fully reliable.

There is one clear exception. The Derbyshire Wye is the only UK river the Wild Trout Trust names as holding a self-sustaining population, with rainbows making up roughly a quarter of the catch alongside wild browns. Past reports of breeding on the Chess, Misbourne and Lambourn do not appear to reflect self-sustaining populations now.

What about harm to native fish? The documented damage, including native fish declines and hybridisation with cutthroat trout, comes mainly from overseas. The Wild Trout Trust describes no specific UK harm, which is not the same as saying there is none. For the current rules on stocking rainbows in Scotland, check with the Scottish Government.

The verdict: a rainbow in a lake was almost certainly stocked, and a self-sustaining wild population in a UK river is, on current evidence, limited to the Derbyshire Wye.

Blue Trout and Other Colour Variants

A blue trout is not a separate species. It is a colour variant of the rainbow trout, and the Wild Trout Trust confirms that golden and blue variants occur among farmed rainbows.

Few suppliers produce them. Northern Trout Fisheries in Yorkshire lists blue trout among its stock and says it is one of the few breeders, so fisheries need to pre-order them.

We could not confirm the cause of the blue colouring from a reliable source, so this guide does not try to explain it.

For the rules, a blue trout is a rainbow. It has the same legal status and the same seasons, and the black-spot check still applies. If you want to target one, ask the fishery whether it stocks them, and check with the fishery before you travel.

Where and When You Can Fish for Rainbows: Seasons and Licences

The commonest mistake is assuming that because you can fish for rainbows all year on a lake, the same applies on a river. It does not.

Stillwaters in England

In England, rainbow trout can be fished all year with rod and line in all stillwaters, according to the GOV.UK local fishing byelaws.

Rivers, streams, drains and canals

On running water and canals, the rainbow trout close season matches the brown trout close season, and it varies by Environment Agency region. The North West region byelaws, for example, set it at 1 October to 14 March, canals included. Check your own region’s byelaws and our fishing seasons guide before you fish a river.

In Wales, check the rainbow trout close season with Natural Resources Wales.

Rod licences

In England and Wales you need a trout and coarse rod licence from age 13, and the licence for 13 to 16 year olds is free. Prices change, so check the current price on GOV.UK and read our fishing licence guide.

In Scotland you do not need a rod licence, but you do need permission from whoever owns the fishing. The exception is the Border Esk region, where an Environment Agency licence is needed even in its Scottish parts, according to GOV.UK. Northern Ireland has its own rules, so check with the relevant Northern Ireland authority.

Where	Close season	Licence
England, stillwater	None, fish all year	Rod licence from age 13
England, river or canal	Matches brown trout, varies by region (North West: 1 Oct to 14 Mar)	Rod licence from age 13
Wales	Check with Natural Resources Wales	Rod licence from age 13
Scotland	Check with the owner of the fishing	Permission, no licence (except Border Esk region)

Day-ticket fisheries also set their own rules on methods (often fly only), bag limits and catch and release. Read the fishery’s rules, and check with the fishery before you travel.

How Rainbow Trout Are Caught Through the Year

On a stocked stillwater, depth matters as much as fly choice, and the right depth shifts with the season. Everything below sits inside whatever the fishery permits.

Fly fishing is the main method on most trout stillwaters. Lure and bait fishing are allowed on some waters, but only where the fishery says so, so check before you set up. If you are new to it, our stillwater fly fishing guide covers the tackle and casting.

Season	Typical approach	Where in the water
Spring	Buzzers, nymphs and lures	Near the surface to mid-water
Summer	Nymphs and buzzers through the day, dry flies early and late	Deeper in the heat of the day, at the surface at dawn and dusk
Autumn	Lures, plus daddy long legs on the surface	Top layers
Winter	Small nymphs on long leaders, retrieved slowly	Deeper and slower

Line choice does the depth work. A floating line keeps flies in the top layer, while an intermediate or sinking line gets them down to fish holding deeper. If nothing is showing, change depth before you change fly.

The trout flies guide covers patterns for each of these approaches.

Many day tickets are catch-and-kill or have set release rules. Follow the fishery’s rules, and if you release a fish, keep it wet and handle it quickly.

On a first day ticket, start with a floating line and a buzzer or small nymph, then go deeper or switch to a lure if the fish are not near the top.

The British Record Rainbow Trout, Explained

Why do 24lb 1oz, 33lb 4oz and 36lb 14oz all get quoted as the British record rainbow trout?

The British Record (rod caught) Fish Committee splits rainbow trout into two categories. Broadly, a resident fish has lived and grown on in the water where it was caught, while a cultivated fish is a farm-reared fish that was stocked recently.

The resident record is settled. On the BRFC game fish list as at June 2019, it stands at 24lb 1oz 4dr (about 10.9 kg), caught by J Hammond at Hanningfield Reservoir, Essex, in 1998. That is a reservoir fish, not a river fish, whatever you may read elsewhere.

The cultivated record is not settled. On the same list, a 36lb 14oz claim was suspended. A 33lb 4oz fish, caught by J Lawson at Watercress Trout Fishery in Devon, was acknowledged but not ratified. Cultivated game fish lists closed to new claims in April 2015.

Read the June 2019 BRFC game fish list and check with the British Record (rod caught) Fish Committee for the current status.

The figure that is safe to quote is the resident record of 24lb 1oz 4dr from Hanningfield.

Frequently asked questions

Are rainbow trout native to the UK?

No. Rainbow trout are native to the Pacific coast of North America and were first shipped to Britain in 1884-85. The brown trout is the only trout native to the UK. See our game fish species guides for the native species.

Can you catch rainbow trout in UK rivers?

Occasionally, but most are stocked or escaped fish. The Derbyshire Wye is the only UK river the Wild Trout Trust names as holding a self-sustaining population. The river close season follows brown trout dates and varies by region, so check our fishing seasons guide first.

How is a rainbow trout different from a salmon or sea trout?

A rainbow trout has black spots only and a pink flank band, and in the UK it is a non-native, stocked fish. The Atlantic salmon and sea trout are native fish that run to sea and return to rivers to spawn. To tell those two apart, see our sea trout vs salmon guide.

Do I need a rod licence for a private trout fishery?

Yes. In England and Wales you need a rod licence from age 13, even on a private stillwater, and the licence for 13 to 16 year olds is free. You also need the fishery's ticket. In Scotland you need permission rather than a licence. See our fishing licence guide.