The brown trout (Salmo trutta) is a species of salmonid ray-finned fish and the most widely distributed species of the genus Salmo, endemic to most of Europe, West Asia and parts of North Africa, and has been widely globally as a game fish.
Brown trout are highly adaptable and have evolved numerous subspecies. These include: the river-dwelling river trout (Salmo trutta morpha fario); the lake-dwelling lake trout (Salmo trutta morpha lacustris), not to be confused with the lake trout of North America); and the anadromous sea trout (Salmo trutta morpha trutta), which upon adulthood migrate downstream to the oceans for much of its life and only returns to fresh water to spawn.
Sea trout in Ireland and Great Britain have many regional names: sewin in Wales, finnock in Scotland, peal in the West Country, mort in North West England, and white trout in Ireland.