Brown trout

The brown trout (Salmo trutta) is a type of carnivorous ray-finned fish and the most common species in the salmonid genus Salmo. It is found naturally in most of Europe, West Asia, and parts of North Africa. Because it is popular among people who like to fish, brown trout have been placed in many places around the world. However, in areas where they are not native, they sometimes cause problems for local wildlife.

Brown trout are very flexible and have developed many different types. There are three main types: the river trout, which lives in rivers; the lake trout, which lives in large lakes (different from the lake trout found in North America); and the sea trout, which spends part of its life in the ocean. Sea trout have many local names depending on where you are, like sewin in Wales, finnock in Scotland, and white trout in Ireland.

All brown trout types lay their eggs in fresh water, usually in the gravel beds of small streams where the water is cold and clear. Sea trout are special because they start their lives in freshwater but move to the oceans as adults, returning only to freshwater to lay eggs. The river and lake types also move between different freshwater places, like rivers and lakes, especially during their breeding time. Scientists are still trying to understand what makes some brown trout choose to live in the ocean while others stay in freshwater.

Description

Brown trout have a slim body with a long, narrow head and a large mouth. They have special teeth on the roof of their mouths arranged in a zig-zag pattern. Unlike their close relative, the Atlantic salmon, their tail fin is shaped like a triangle and does not split into two parts. They often have dark and red spots on their sides, but these spots do not reach their tail. Young brown trout, called parr trout, usually have a red edge on a small fat fin and dark spots along their sides that fade as they grow older.

These fish can change color depending on where they live. In freshwater, they may look silver with few spots and a white belly, or they might have a brassy reddish-brown color that fades to a creamy white on the belly, with spots surrounded by lighter rings. Some brown trout, like the "Loch Leven" type, have larger fins, a slimmer body, and many black spots but no red spots. Another type found in Europe has a lighter golden color with some red spots and fewer dark spots. Brown trout can vary a lot even within these general descriptions.

Brown trout are medium-sized fish. Some can grow to be about 100 cm long and weigh as much as 20 kg, but in smaller rivers, they often weigh around 1 kg or less when fully grown. One well-known type, the lake trout, usually measures between 40 and 80 cm long, with some reaching up to 140 cm and weighing about 27 kg.

These fish eat many things, including insects, small fish, frogs, tadpoles, mice, and even small birds. They are especially known for eating insect larvae, pupae, nymphs, and adults, which makes them popular for fly fishing. Brown trout can live up to 20 years, though many males die after spawning. They are active both during the day and at night and adapt well to different environments.

Taxonomy

The brown trout's scientific name is Salmo trutta. The word trutta comes from Latin and means "trout". In 1758, a scientist named Carl Linnaeus described the brown trout in a book called Systema Naturae. This book helped create a way to name animals. Linnaeus used Salmo trutta for trout that live in both rivers and the sea. He also gave names to river trout (Salmo fario) and lake trout (Salmo lacustris).

Range

The native range of brown trout stretches from northern Norway and White Sea tributaries in Russia in the Arctic Ocean to the Atlas Mountains in North Africa. In the west, their natural range includes Iceland in the north Atlantic, and it extends east to Aral Sea tributaries in Afghanistan and Pakistan.

Brown trout have been introduced to many parts of the world beyond their natural range. They now live in North and South America, Australasia, Asia, and South and East Africa. The first introductions happened in Australia in 1864, when brown trout eggs were brought from the River Itchen to Melbourne. From there, they spread to many rivers and lakes. Similar introductions took place in South Africa in the late 1800s and in the Himalayas by the early 1900s. In the Americas, brown trout were first introduced to Canada in 1883 and later to Argentina, Chile, Peru, and the Falklands. In the United States, the first brown trout were released into the Baldwin River in Michigan in 1884, and they quickly became established in many states.

Conservation status

The brown trout is not considered endangered, but some groups of these fish face challenges. Problems include damage to their homes, too many people catching them, and adding other fish that mix with them. When the water gets too warm in summer, it can hold less oxygen, which sometimes causes fish to die off if they cannot find cooler, oxygen-rich areas.

Catching too many large female fish reduces the number of eggs they can lay, affecting future populations. In small streams, brown trout help control other small water creatures, so fewer trout can change the whole balance of life in the water. Climate change is also a concern because brown trout prefer cooler water. They like to hide near rocks, logs, and plants for protection from danger and harsh sunlight. Deep or fast-moving water also helps them stay safe during extreme weather.

Diet

Brown trout eat many small animals, with tiny water creatures being their favorite food. As they grow bigger, they may also eat other fish. This change in what they eat helps them share food better with other brown trout.

When brown trout are very young, it is important for them to start eating right away. They begin eating small creatures like tiny water worms even before they finish growing out of their baby stage.

Relationship with humans

Stocking and trout farming

Brown trout have been introduced to many places around the world, including North America, South America, Australia, and New Zealand, for sport fishing. The first introduction in the United States happened on April 11, 1884, in Michigan. While they are valued as a game fish, brown trout can sometimes harm local fish species in new areas by competing with them or eating their young.

Angling

Brown trout have been popular among fishers for many centuries. Ancient Roman writer Aelian described fishing for trout with flies around 200 AD. Important books about fishing, like The Treatyse of Fysshynge with an Angle from 1496 and The Compleat Angler from 1653, focused on brown trout. Over time, special fishing methods were developed for catching them. When brown trout were brought to the United States in the 1880s, they became a favorite subject for American fishers too.

In places like Yellowstone National Park, introducing brown trout created exciting new fishing spots. Today, many areas around the world have successful brown trout fisheries, attracting fishers from everywhere.