Brown trout
The
brown trout is an originally European species of salmonid fish. It includes both purely freshwater populations, referred to
Salmo trutta morpha
fario and
S. trutta morpha
lacustris, and anadromous forms known as the
sea trout,
S. trutta morpha
trutta. The latter migrates to the oceans for much of its life and returns to freshwater only to spawn. Sea trout in the UK and Ireland have many regional names, including sewin, finnock, peal, mort and white trout. The specific epithet
trutta derives from the Latin
trutta, meaning, literally, "trout". The lacustrine morph of brown trout is most usually potamodromous, migrating from lakes into rivers or streams to spawn, although evidence indicates stocks spawn on wind-swept shorelines of lakes.
S. trutta morpha
fario forms stream-resident populations, typically in alpine streams, but sometimes in larger rivers. Anadromous and nonanadromous morphs coexisting in the same river appear genetically identical. What determines whether or not they migrate remains unknown.