2007 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and Fish

Rainbow trout, Oncorhynchus mykiss
Rainbow trout, Oncorhynchus mykiss
Biwa trout, Oncorhynchus masou subsp
Biwa trout, Oncorhynchus masou subsp

Trout is the common name given to a number of species of freshwater fish belonging to the salmon family, Salmonidae.

All fish called trout are members of the subfamily Salmoninae. The name is commonly used for species in three of the seven genera in the sub-family: Salmo, which includes Atlantic species; Oncorhynchus, which includes Pacific species; and Salvelinus, which includes fish also sometimes called char or charr. Fish referred to as trout include:

  • Genus Salmo
    • Adriatic trout, Salmo obtusirostris
    • Brown trout, Salmo trutta
    • Flathead trout, Salmo platycephalus
    • Marmorata, Soca River trout or Soča trout - Salmo trutta marmoratus
    • Ohrid trout, Salmo letnica
    • Sevan trout, Salmo ischchan
  • Genus Oncorhynchus
    • Apache trout, Oncorhynchus apache
    • Seema, Oncorhynchus masou subsp
    • Cutthroat trout, Oncorhynchus clarki
    • Gila trout, Oncorhynchus gilae
    • Golden trout, Oncorhynchus aguabonita
    • Rainbow trout, Oncorhynchus mykiss
  • Genus Salvelinus (Char)
    • Aurora trout, Salvelinus fontinalis timagamiensis
    • Brook trout, Salvelinus fontinalis
    • Bull trout, Salvelinus confluentus
    • Dolly Varden trout, Salvelinus malma
    • Lake trout, Salvelinus namaycush
    • Silver trout, † Salvelinus fontinalis agassizi (extinct)

Trout are usually found in cool, clear streams and lakes, although many of the species have anadromous strains, as well. They are distributed naturally throughout North America, northern Asia and Europe. Several species of trout were introduced to Australia and New Zealand by amateur fishing enthusiasts in the 19th century, effectively displacing several upland native fish species. The species introduced included brown trout from England and rainbow trout from California. The rainbow trout were a steelhead strain generally accepted as coming from Sonoma Creek. The rainbow trout of New Zealand still show that steelhead tendency to run up rivers in winter to spawn.

Trout have fins entirely without spines, and all of them have a small adipose (fatty) fin along the back, near the tail. There are many species, and even more populations that are isolated from each other and morphologically different. However, many of these distinct populations show no significant genetic differences, and therefore what may appear to be a large number of species is considered a much smaller number of distinct species by most ichthyologists.

The trout found in the eastern United States are a good example of this. The brook trout, the aurora trout and the (extinct) silver trout all have physical characteristics and colourations that distinguish them, yet genetic analysis shows that they are one species, Salvelinus fontinalis.

Lake trout (Salvelinus namaycush), like brook trout, actually belong to the char genus. Lake trout inhabit many of the larger lakes in North America and live much longer than rainbow trout which have an average maximum life span of 7 years. Lake trout can live many decades and can grow to more than 30 kg (66 pounds).

Rainbow trout, Oncorhynchus mykiss
Rainbow trout, Oncorhynchus mykiss

Trout generally feed on soft bodied aquatic invertebrates, such as flies, mayflies, caddisflies, stoneflies, and dragonflies. In lakes, various species of zooplankton often form large parts of the diet. In general, the larger specimens of trout (longer than about 30 cm) prey almost exclusively on small fish, if they are available.

As a group, trout are somewhat bony, but the flesh is generally considered to be tasty. Additionally, they provide a good fight when caught with a hook and line, and are sought after recreationally. Because of their popularity, trout are often raised on fish farms and planted into heavily fished waters in an effort to mask the effects of overfishing. While they can be caught with a normal rod and reel, fly fishing is a distinctive method developed primarily for trout and now extended to other species. Farmed trout and char are also sold commercially as food fish.

Trout that live in different environments can have dramatically different colorations and patterns. Mostly, these colors and patterns form as camouflage, based on the surroundings, and will change as the fish moves to different habitats. Trout in, or newly returned from the sea, can look very silvery, while the same "genetic" fish living in a small stream or in an alpine lake could have pronounced markings and more vivid coloration. It is virtually impossible to define a particular colour pattern as belonging to a specific breed; however, in general, wild fish are claimed to have more vivid colors and patterns.

Golden trout, Oncorhynchus aguabonita
Golden trout, Oncorhynchus aguabonita

The cutthroat trout has 14 recognized subspecies (depending on your sources), such as the Lahontan cutthroat trout, Oncorhynchus clarki henshawi, Bonneville cutthroat trout, Oncorhynchus clarki utah, Colorado River cutthroat trout, Yellowstone cutthroat trout.

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