Habitat/Distribution. Like most members of the Salmonidae family, trout are in some way associated with cold, often rushing waters and high oxygen demands. Some—including the brown trout, the cutthroat, and the rainbow— have forms that are also tied to the sea and spend a portion of their lives there. The Pacific salmon, the Atlantic salmon, and the arctic charr are all examples of this. All trout spawn in freshwater and most require cold running water.
Some trout, especially the brown, have a lineage of historical, cultural, and angling significance, especially in Europe. All are good table fare and esteemed sportfish. They include species with a limited range, especially various strains and isolated populations that are little known to most people, and species that have been distributed virtually around the world. Rainbow trout are likely the most widely spread game-fish worldwide and have become important food fish
The word "trout" is used to describe various related members of the Salmonidae family, which also includes salmon, charr, whitefish, and grayling. As a group, these fish are endemic to freshwaters of the temperate and cool regions of the Northern Hemisphere but have been introduced widely outside their native range. Species that are commonly referred to as trout occur not only in the true trout genus Salmo, but also in the Pacific salmon genus Oncorhynchus and the charr genus Salvelinus, which complicates both a definition and an explanation of what a trout is.
Species. Among the most popular and widely known species of fish that are called trout are brook trout, brown trout, cutthroat trout, rainbow trout, and lake trout; these have many strains, sea-run forms, and hybrid versions.
Some taxonomists would argue that the brown trout is the only true trout, as it was the first of its kind described by Linnaeus, the father of modern taxonomy, and that other fish species have been labeled trout (especially in North America) largely because of their similar body form. This issue is best left to scientists, but from a technical standpoint it should be noted that such commonly known species as lake trout and brook trout are actually members of the charr group. So is the lesser-known bull trout. Likewise, the rainbow trout and its anadromous steelhead variation, which was once placed in the trout genus, is now a member of the Pacific salmon group, as are the cutthroat trout, the lesser-known golden trout, and the Apache trout.
Identification. As a rather primitive group of fish, trout lack spines in the fins. Most of the soft rays in the fins are branched. The pelvic fins are situated far back on the trout's body—in the "hip" region, where the legs of amphibians articulate with the body. This placement contrasts with the location of the pelvic fins in many other species, like the largemouth bass, for example, whose pelvic fins are so far forward, they are almost directly beneath the pectoral fins. Other indications of the trout's primitive nature are the possession of an adipose fin and a primitive air bladder.
Trout as a group are among the most distinguished-looking and prettiest freshwater fish. Some are especially colorful, particularly in spawning mode, and most have distinctive body markings, although there are great variations, depending on the environment. Within each species there is considerable variation in color and markings from one river to another, as well as between river and lake populations. The brown trout found deep in a lake, for example, are more silvery and rather bland, compared to brown trout caught in a rich limestone stream; so great is the difference that the casual observer would not assume that the two were the same species.
Issues. Like nearly all members of the Salmonidae family, trout have suffered from changes wrought by humans. These include overfishing, pollution, habitat alteration, factors that have caused a warming of waters, hatchery impacts, and competition from exotic species.
Some native populations of the various trout and their subspecies or strains have declined dramatically or have even been extirpated, although others have declined and recovered or expanded. Competition between species, especially between native and introduced trout, or between trout and other introduced species, has often been a great problem.
Each of the major trout species is of great interest to anglers, although rainbow trout and brown trout have the greatest following because of their suitability to diverse habitats and wide international distribution. Trout are generally associated with river and stream fishing, especially wading and casting activities, although a great many anglers pursue these fish from various types of boats in large rivers and lakes, making it possible to fish for them in a multitude of ways.
through aquaculture production. As a group, trout are among the most widely cultivated fish, perhaps second only to carp, which are the mainstay of fish farming in China. Trout have been widely planted to supplement existing stocks, reintroduce species to waters where natural populations were extirpated, or introduce them to waters where they did not previously exist.
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