A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish). At 32,000 species, fish exhibit greater species diversity than any other group of vertebrates.

Fish are an important resource worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries (see fishing) or farm them in ponds or in cages in the ocean (see aquaculture). They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.

Because the term "fish" is defined negatively, and excludes the tetrapods (i.e., the amphibians, reptiles, birds and mammals) which descend from within the same ancestry, it is paraphyletic, and is not considered a proper grouping in systematic biology. The traditional term pisces (also ichthyes) is considered a typological, but not a phylogenetic classification.

The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods.

Read more about Fish:  Evolution, Diversity of Fish, Diseases, Conservation

Other articles related to "fish":

Trumpeter (disambiguation) - Animals
... Swan, a large swan, sometimes informally called a "trumpeter" Fish Trumpeter (fish), a family of marine fish Latridae Trumpeter whiting (Sillago maculata) Yellowtail ...
Namor - Powers and Abilities - Formerly Depicted Abilities
... eel!" In the same issue, "the radar sense of the cave fish from the lowest depths of the sea" enables him to sense the presence of Sue Storm when she is invisible ... the former he also manifests the power to inflate his body like a puffer fish ... Namor has since lost his power to imitate the characteristics of fish..." His electrical abilities were, however, seen out of comic continuity in 1991's Spider-Man The Video Game ...
Oily Fish
... Oily fish have oil in their tissues and in the belly cavity around the gut ... Examples include small forage fish, such as sardines, herring and anchovies, and other larger pelagic fish, such as salmon, trout, ilish and mackerel ... Oily fish can be contrasted with whitefish, which contain oil only in the liver, and much less overall than oily fish ...
Petersburg, Alaska - History
... The north end of Mitkof Island was a summer fish camp utilized by Kake Tlingits from Kupreanof Island ... Remnants of fish traps and some petroglyphs have been carbon-dated back some 2,000 years ... number of icebergs from the nearby LeConte Glacier which would provide a source for cooling fish) ...
Finnish Cuisine - Finnish Food - Fish
... Lakes in Finland provide many opportunities for fishing and fish has always been an important protein source ... Several ways to prepare fish are used, including frying, boiling, drying, salting, fermenting, cold smoking or simply slicing sea fish and eating it raw ... It is common to smoke any types of fish, like salmon, zander, pike, perch and Baltic herring ...

Famous quotes containing the word fish:

    All the fish in us
    had escaped for a minute.
    The real fish did not mind.
    We did not disturb their personal life.
    Anne Sexton (1928–1974)

    Reason is a supple nymph, and slippery as a fish by nature. She had as leave give her kiss to an absurdity any day, as to syllogistic truth. The absurdity may turn out truer.
    —D.H. (David Herbert)

    Come, thou shalt go home, and we’ll have flesh for holidays, fish for fasting-days, and moreo’er puddings and flap-jacks, and thou shalt be welcome.
    William Shakespeare (1564–1616)