Trout


Trout is a generic common name for numerous species of carnivorous freshwater fishes belonging to the genera Oncorhynchus, Salmo, and Salvelinus, all of which are members of the subfamily Salmoninae in the family Salmonidae. The word trout is also used for some similar-shaped but non-salmonid fish, such as the spotted seatrout/speckled trout.
Trout are closely related to salmon and have similar migratory life cycles. Most trout are strictly potamodromous, spending their entire lives exclusively in freshwater lakes, rivers and wetlands and migrating upstream to spawn in the shallow gravel beds of smaller headwater creeks. The hatched fry and juvenile trout, known as alevin and parr, will stay upstream growing for years before migrating down to larger waterbodies as maturing adults. There are some anadromous species of trout, such as the steelhead and sea trout, that can spend up to three years of their adult lives at sea before returning to freshwater streams for spawning, in the same fashion as a salmon run. Brook trout and three other extant species of North American trout, despite the names, are actually char, which are salmonids also closely related to trout and salmon.
Trout are classified as oily fish and have been important food fish for humans. As mid-level predators, trout prey upon smaller aquatic animals including crustaceans, insects, worms, baitfish and tadpoles, and themselves in turn are also important staple prey items for many animals, including brown bears, otters, raccoons, birds of prey, gulls, cormorants and kingfishers, and other large aquatic predators. Discarded remains of trout also provide a source of nutrients for scavengers, detrivores and riparian florae, making trout keystone species across aquatic and terrestrial ecosystems.

Species

The name "trout" is commonly used for many species in three of the seven genera in the subfamily Salmoninae: Salmo, Oncorhynchus and Salvelinus. Fish species referred to as trout include:
File:Marble trout from zadlaščica.jpg|upright=1.35|thumb|Salmo: marble trout, S. marmoratus
File:Rainbow Trout.jpg|thumb|upright=1.35|Oncorhynchus: rainbow trout, O. mykiss
File:Brook trout 1918.jpg|upright=1.35|thumb|Salvelinus: brook trout, S. fontinalis
  • Genus Salvelinus, five of the 52 extant species
  • * Brook trout, Salvelinus fontinalis
  • ** Aurora trout, S. f. timagamiensis
  • * Bull trout, Salvelinus confluentus
  • * Dolly Varden trout, Salvelinus malma
  • * Lake trout, Salvelinus namaycush
  • * Silver trout, † Salvelinus agassizi
  • Hybrids
  • * Tiger trout, Salmo trutta X Salvelinus fontinalis
  • * Speckled Lake trout, ''Salvelinus namaycush X Salvelinus fontinalis''

    Fish from other families

  • Pseudaphritidae
  • * Genus Pseudaphritis
  • **Sand trout, Pseudaphritis urvillii
  • Sciaenidae
  • * Genus Cynoscion
  • ** Spotted sea-trout, ''Cynoscion nebulosus''

    Anatomy

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 fish living in a small stream or in an alpine lake could have pronounced markings and more vivid coloration; it is also possible that in some species, this signifies that they are ready to mate. In general, trout that are about to breed have extremely intense coloration and can look like an entirely different fish outside of spawning season. It is virtually impossible to define a particular color pattern as belonging to a specific breed; however, in general, wild fish are claimed to have more vivid colors and patterns.
Trout have fins entirely without spines, and all of them have a small adipose fin along the back, near the tail. The pelvic fins sit well back on the body, on each side of the anus. The swim bladder is connected to the esophagus, allowing for gulping or rapid expulsion of air, a condition known as physostome. Unlike many other physostome fish, trout do not use their bladder as an auxiliary device for oxygen uptake, relying solely on their gills.
There are many species, and even more populations, that are isolated from each other and morphologically different. However, since many of these distinct populations show no significant genetic differences, 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 silver trout all have physical characteristics and colorations that distinguish them, yet genetic analysis shows that they are one species, Salvelinus fontinalis.
Lake trout, like brook trout, 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 lifespan of seven years. Lake trout can live many decades, and can grow to more than.

Habitat

As salmonids, trout are coldwater fish that are usually found in cool, clear streams, wetlands and lakes, although many of the species have anadromous populations as well. Juvenile trout are referred to as troutlet, troutling or parr. 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 and endangering several upland native fish species. The introduced species included brown trout from England and rainbow trout from California. The rainbow trout has a steelhead subspecies, generally accepted as coming from Sonoma Creek. The rainbow trout of New Zealand still show the steelhead tendency to run up rivers in winter to spawn.
In Australia, the rainbow trout was introduced in 1894 from New Zealand and is an extremely popular gamefish in recreational angling.
Despite severely impacting the distribution and abundance of native Australian fish, such as the climbing galaxias, millions of rainbow and other trout species are released annually from government and private hatcheries.
The closest resemblance of seema trout and other trout family can be found in the Himalayan Region of India, Nepal, Bhutan, Pakistan and in Tian Shan mountains of Kyrgyzstan.

Diet

Trout generally feed on other fish, and soft-bodied aquatic invertebrates, such as flies, mayflies, caddisflies, stoneflies, mollusks and dragonflies. In lakes, various species of zooplankton often form a large part of the diet. In general, trout longer than about prey almost exclusively on fish, where they are available. Adult trout will devour smaller fish up to one-third of their length. Trout may feed on shrimp, mealworms, bloodworms, insects, small animal parts, and eel.
Trout who swim the streams love to feed on land animals, aquatic life, and flies. Most of their diet comes from macroinvertebrates, or animals that do not have a backbone like snails, worms, or insects. They also eat flies, and most people who try to use lures to fish trout mimic flies because they are one of trout's most fed on meals. Trout enjoy certain land animals, including insects like grasshoppers. They also eat small animals like mice when they fall in. They consume a diet of aquatic life like minnows or crawfish as well. Trout have a diverse diet they follow; they have plenty of different options.