Brown Trout - Salmo Trutta Fario

About the Brown Trout.
The brown trout is one of the few species of fish that is native to the British Isles. It can be found in practically every river system of the UK, as well as many fisheries, still waters and lakes, although this is mainly due to artificial introduction. Many brown trout have been farm-reared and are normally much larger than those reared in the wild.
The brown trout belongs to the Salmonidae family, together with the rainbow trout and the Atlantic salmon. The brown trout and Atlantic salmon belong to the Salmo genus of the Salmoniae, a sub-category of the Salmonidae family, whilst the rainbow trout belongs to the Oncorhynchus genus.

After much discussion and debate amongst scientists about the number of species of trout, it has now been agreed that the ferox, sea trout, bull trout and various other sub-categories are actually all variations of the same species - the brown trout.

Unlike the Atlantic salmon and the sea trout, the brown trout is a freshwater fish and does not migrate to the sea. It generally stays in the same area once it has found an ideal spot for food and shelter, only migrating to shallow gravely areas to spawn.

Brown Trout Identification

The colouring of the brown trout is different according to its habitat. This is mainly so that it can blend in to its surroundings and camouflage itself from predator's eyes.

However, most brown trout are an olive - golden brown colour with a darker back and lighter flanks. Its belly is a creamy colour and it has large dark brown spots covering its body and head with occasional red ones dotted in between. Younger brown trout have blue - grey spots on their body.

As with all members of the salmon family, the brown trout has a ray-less adipose fin. It also has an anal fin consisting of about 10 soft rays but no spines and its dorsal fin is also rayed.

The head is small, yet the mouth is large and filled with rows of numerous small teeth. It also has a ridge of sharp teeth along the roof of its mouth, known as the vomerine teeth. The brown trout has a long upper jawbone that goes back well past its eye level.

The brown trout is similar in shape to the salmon, in that it has a strong streamlined body, although it doesn't grow as long.

Brown Trout Habitat

The brown trout is originally native to Europe and western Asia although nowadays it is found in many parts of the USA and Australia as well.

Within the UK, Scotland is particularly popular for trout fishing and this species is plentiful there, due to its preference for cold, fast-flowing, unpolluted and well-oxygenated waters.

This fish is generally found in the upper reaches of the river, in small chalk streams or stream inlets.

Brown trout are also found in many still waters such as lakes and lochs provided that they are clean and cold. The brown trout is not able to survive in waters that are higher than 21°C and they also require high levels of oxygen for their survival.

The brown trout is not migratory and stays in fresh water all its life, unlike the migratory sea trout, a travelling brother of the brown trout.

The brown trout is a fan of cover and shelter within the water and can often be found hiding under fallen trees, overhanging bushes or behind boulders. These areas provide good hiding places from predators and shade from the sun, as well as being excellent spots for food sources. The brown trout does not generally venture very far and therefore rivers with fast-flowing water often carry food to the fish as it passes downstream. The brown trout often hang about in areas away from the strong current such as undercut banks and behind boulders.

In stillwaters the fish will have to swim around a bit more in search of food, which can often be found along the edges, around vegetation and on the lake bed. The brown trout will approach the surface of the water at night when it is cooler, to catch insects, especially in the warmer months when they are more active.

Natural Brown Trout Food

When the brown trout is born it feeds on nutrients found in the yolk sac that is attached to its side. After this it will move on to insect larvae and from there it will begin to feed on more substantial meals such as aerial and terrestrial insects, crustaceans and molluscs with the occasional small fish, amphibian such as the frog or even small rodent.

Brown trout generally feed at night when the temperature is lower but may feed in the daytime in winter and early spring.

Brown trout are often very selective eaters, sometime choosing to feed on only one species of insect. Mayfly and nymphs are particularly popular, which anglers should take into consideration when choosing their bait.

Brown Trout Reproduction

Once the brownie, as it is often referred to has found its ideal home, it generally does not budge. It will only move away once it is time to spawn, usually between November and January, when it travels upstream to shallow, fast-flowing gravely waters.

As with the salmon and sea trout, the female digs a hollow in the gravel bed by flapping her caudal fin to loosen and dislodge stones aided by the current of water brought about from this movement.

She then deposits her eggs, which are fertilised by a male companion, subsequently covering them up by brushing the gravel and stones over the top.

The female brown trout typically carries around 900 eggs per pound of body weight, which she nurtures in her swollen belly evident prior to spawning.

The eggs commonly take around 4 weeks to hatch although in very cold waters this could be increased to several months. Similarly, cold water slows the growth of the newly born and it could be two years before the young parr reaches adult stage.

The Brown Trout's Vital Statistics

  • Average weight: 12oz (340g) in rivers and 3lb (1.4kg) in stillwaters
  • Average length: around 19.7 inches (50cm)
  • Specimen weight: 5lb (2.3kg) and over
  • Life-span: between 6 and 13 years
  • UK natural brown trout record: 31lb 12oz (Loch Awe, Scotland))
  • UK cultivated brown trout record: 21lb 3oz (9.5kg) (Denver Springs Fishery, Hampshire)

Rivers with big brown trout include:


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