The brown trout (Salmo trutta) is a species of carnivorous ray-finned fish and the most widely distributed species of the salmonid genus Salmo, endemic to most of Europe, West Asia and parts of North Africa, and has been widely introduced globally as a game fish, even becoming one of the world's worst invasive species outside of its native range. Brown trout are highly adaptable and have evolved numerous ecotypes/subspecies. These include three main ecotypes: a riverine ecotype S. trutta morpha fario, commonly called river trout; a lacustrine ecotype S. trutta morpha lacustris, also called the lake trout (not to be confused with the lake trout in North America, which is a species of char); and an euryhaline ecotype S. trutta morpha trutta, also known as the sea trout. 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. Like all salmonids, all three brown trout ecotypes spawn in fresh water among the gravel beds of headstreams, where the water is colder and better aerated. Sea trout is anadromous, meaning it will spend the juventile life stages in freshwater, but upon reaching adulthood will migrate downstream to the oceans for much of its life, and only returns to fresh water for reproduction. In contrast, the lacustrine and riverine morphs are both potamodromous, meaning they are also migratory but only between different freshwater bodies. Lacustrine trout mainly inhabit large lakes with calm and stratified deep water, while riverine trout forms fluvial populations typically in large rivers but sometimes in shallower creeks and alpine streams, both still migrating upstream during reproductive seasons. Anadromous and potamodromous morphs coexisting in the same river appear genetically identical. What determines whether they migrate to sea or not remains unknown.
Description
Defining characteristics of brown trout include a slender body with a long, narrow head. The mouth is large, and on its roof, vomerine teeth are developed in a zig-zag pattern. The caudal fin is deltaform without forking, unlike that of the related Atlantic salmon (Salmo salar). Dark and red spots are often present on the sides, but do not extend to the tail. Parr trout (juvenile) often have a red margin on their adipose fin, with dark blotches along their sides that also become inconspicuous with age. Freshwater brown trout range in colour from largely silver with relatively few spots and a white belly, to the more well-known brassy reddish-brown cast fading to creamy white on the fish's belly, with medium-sized spots surrounded by lighter halos. The more silver forms can be mistaken for rainbow trout. Regional variants include the so-called "Loch Leven" trout, distinguished by larger fins, a slimmer body, and heavy black spotting, but lacking red spots. The continental European strain features a lighter golden cast with some red spotting and fewer dark spots. Notably, both strains can show considerable individual variation from this general description. Early stocking efforts in the United States used fish taken from Scotland and Germany.
Brown trout is a medium-sized fish, growing to 20 kg (44 lb) or more and a length of about 100 cm (39 in) in some localities, although in many smaller rivers, a mature weight of 1.0 kg (2.2 lb) or less is common. S. t. lacustris reaches an average length of 40–80 cm (16–31 in) with a maximum length of 140 cm (55 in) and about 60 lb (27 kg). On September 11, 2009, a 41.45-lb (18.80-kg) brown trout was caught by Tom Healy in the Manistee River system in Michigan, setting a new state record. As of late December 2009, the fish captured by Healy was confirmed by both the International Game Fish Association and the Fresh Water Fishing Hall of Fame as the new all-tackle world record for the species. This fish, which supplanted the former world record from the Little Red River in Arkansas, has in turn been exceeded by a 20.1-kilogram (44 lb) specimen caught in the Ohau Canal in Twizel, New Zealand on 27 October 2020. The all-tackle length IGFA world record is a 97-centimetre (38 in) fish caught in Milwaukee Harbor, Wisconsin on 16 December 2011.
The spawning behaviour of brown trout is similar to that of the closely related Atlantic salmon. A typical female produces about 2,000 eggs per kg (900 eggs per lb) of body weight. Brown trout can live 20 years, but as with the Atlantic salmon, a high proportion of males die after spawning, and probably fewer than 20% of anadromous female kelts recover from spawning . The migratory forms grow to significantly larger sizes for their age due to abundant invertebrate prey and forage fish in the waters where they spend most of their lives. Sea trout are more commonly female in less nutrient-rich rivers. Brown trout are active both by day and by night and are opportunistic feeders. While in freshwater, brown trouts are generalistic mesopredators and their diets frequently include invertebrates (insects, crustaceans, molluscs and benthic worms from the streambed), other fish, frogs (especially tadpoles) and sometimes even mice and small birds, and it is not uncommon for brown trout to breach the water surface in order to catch low-flying terrestrial insects. The high dietary reliance upon insect larvae, pupae, nymphs and adults allows trout to be a favoured target for fly fishing. Sea trout are fished for especially at night using wet flies, which imitate drowning insects. Brown trout can also be caught with lures such as spoons, spinners, jigs, plugs, plastic worm imitations, and live or dead baitfish. Brown trout rarely form hybrids with other species; if they do, they are almost invariably infertile. One such example is the tiger trout, a hybrid with the brook trout.
Taxonomy
The scientific name of the brown trout is Salmo trutta. The specific epithet trutta derives from the Latin trutta, meaning, literally, "trout". Behnke (2007) relates that the brown trout was the first species of trout described in the 1758 edition of Systema Naturae by Swedish zoologist Carl Linnaeus. Systema Naturae established the system of binomial nomenclature for animals. Salmo trutta was used to describe anadromous or sea-run forms of brown trout. Linnaeus also described two other brown trout species in 1758. Salmo fario was used for riverine forms. Salmo lacustris was used for lake-dwelling forms.
Range
… excerpt ends here. Continue reading the full article.
