Brown Trout and Sea Trout
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: Animalia : Chordata : Actinopterygii : Salmoniformes : Salmonidae : Salmo : trutta
Trinomial name
Salmo trutta fario Salmo trutta trutta

The Brown Trout (Salmo trutta fario) and the Sea Trout (Salmo trutta trutta) are fish distinguished chiefly by the fact that the Brown Trout is largely a freshwater fish, while the Sea Trout shows anadromous reproduction , spawning in fresh water but migrating to the oceans for much of its adult life. The common name "Brown Trout" is often applied to both subspecies.

The species is native to Europe and Asia, but has been widely introduced for purposes of sport into North America, South America, Australia and New Zealand, for all of which it is a potential pest species. There are also landlocked populations far from the oceans, for example in Greece and Estonia. Because of the trout's importance as a food and game fish, it has been artificially restocked in many places in its range, and natural populations probably exist only in isolated places, for example Corsica.

The natural distribution of the migratory forms may be circumpolar, and the fish is not considered to be endangered. It prefers cold, well-oxygenated upland waters, especially large streams in mountainous areas. Cover is important to trout, and they are more likely to be found where there are submerged rocks, undercut banks, and overhanging vegetation.

The Brown trout is a medium sized fish, growing to 20 kg or more and living for several years; the migratory forms are reported to grow to larger sizes and live longer. It is active mainly by day. Trout feed on invertebrates from the river floor, insect larvae, molluscs, small fish and frogs, and aerial insects; the last element in their diet is what allows trout to be a favoured target for fly fishing.

The life history and spawning behaviour of the migratory forms is similar to that of salmon. Each female produces about 10,000 eggs at spawning.

Trout is a favourite food fish, and is used both fresh and smoked; there are many recipes for it, and it may be eaten fried, grilled, baked or microwaved.