The trout has a fusiform body, slightly compressed laterally, with a broad caudal peduncle and an adipose fin between the dorsal and tail; the color varies from brownish-brown on the back and flanks, with red and black spots framed in pale halos, to yellowish-white on the abdomen. Males and females can reach lengths of up to 70 cm in rivers and up to 140 cm in lakes or the sea (record of 140 cm). This species is native to the river basins of Europe, North Africa and West Asia, but has been introduced to many temperate and cold regions of North America, Asia and Oceania, adapting to both potamodromous (river) and lacustrine or anadromous (sea) environments.
Habits
Trout are predominantly solitary and territorial, establishing feeding territories as juveniles; they feed diurnally, mainly on insect larvae, crustaceans, and small fish, hunting both on the rocky substrate and in the water column, and move rapidly by swimming or jumping to avoid predators.
Reproduction
Brown trout spawn between October and January (in the Northern Hemisphere), forming several shallow depressions in the river gravel with vigorous tail movements, where the female deposits 1,000–1,500 eggs in each nest. The larvae hatch after 2–4 months and remain protected in the gravel for another 2–3 weeks before starting to feed in the water column.
Distribution
Native to the cold and temperate basins of Europe, North Africa and Western Asia, the trout has been successfully introduced to most cold-water regions of North America, Asia and Oceania. It occupies mountain and lowland rivers, lakes and near the sea coast, preferring clear, well-oxygenated waters and rocky substrates for reproduction.
