The Brown Trout is a typical fish of the salmon family inhabiting mountain streams, rivers and lakes, characterized by its vivid and variable coloring. Immature fish have large, conspicuous grey-blue spots on their sides, while the maturer specimens have small, red flecks, often edged with light shades. The belly is yellow-white to yellow. In autumn and winter it migrates upstream to spawn. The fertilized eggs are deposited by the female into a bowl-shaped depression on the river bed.
The size of this trout is closely related to its habitat; in the fast-flowing waters of mountain streams they can reach a length of about 20 cm and weigh about 100 g; however, in lowland rivers rich in food they grow to a length of 60 cm and a weight of about 2 kg. It lives predominantly on water insects and their larvae, as well as other small water animals, whilst the larger specimens often hunt for other fish, including members of their own species.