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fish,limbless aquatic vertebrate animal with fins and internal gills. Traditionally the living fish have been divided into three class: the primitive jawless fishes, or Agnatha; the cartilaginous (sharklike) fishes, or Chondrichthyes; and the bony fishes, or Osteichthyes. These groups, although quite different from one another anatomically, have certain common features related to their common evolutionary origins or to their aquatic way of life. Fish were the earliest vertebrates and presumably evolved from a group of aquatic lower chordates (see ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information. ); the terrestrial vertebrates evolved from fishes. More recent cladistic taxonomies, relying on evolutionary relationships determined through DNA studies, group the living fish into five classes, dividing the jawless fishes into Myxini (hagfish) and Petromyzontida (lampreys) and the bony fishes into Actinopterygii (ray-finned fish) and Sacropterygii (lobe-finned fish).
There are some 28,000 living species of fish, the vast majority of which are bony fishes. They range in size from the .31-in. (7.9-mm) Paedocypris that lives in tropical swamps in Sumatra to the 45-ft (14-m) whale shark. Many are brightly colored, and many have shapes and patterns that serve as camouflage. They are found in all marine, fresh, and brackish waters throughout the world and at all depths. Members of different species of fish tolerate water temperatures ranging from freezing to over 100°F; (38°C;). Most are confined either to saltwater or to freshwater, but some are physiologically adapted to moving from one to the other. A number of fishes that are born in freshwater spend their adult lives in the ocean, returning to their birthplace to spawn; the reverse of this migration occurs in some fishes born in the ocean. Many fishes stay in tightly organized groups, called schools; others are solitary and congregate only for feeding and spawning. Fish may be carnivorous, herbivorous, or omnivorous. Some fish are scavengers on lake or ocean bottoms. Fish are a major source of human food as well as of oil, fertilizer, and feed for domestic animals (see fishingfishing,
act of catching fish for consumption or display. Fishing—usually by hand, club, spear, net, and (at least as early as 23,000 years ago) by hook—was known to prehistoric people.
..... Click the link for more information. ).
A number of aquatic invertebrate animals and groups have common names that include the term fish (for example, crayfish and shellfish), but these do not resemble and are not related to true fishes. Furthermore, there are members of the terrestrial vertebrate classes, such as whaleswhale,
aquatic mammal of the order Cetacea, found in all oceans of the world. Members of this order vary greatly in size and include the largest animals that have ever lived. Cetaceans never leave the water, even to give birth.
..... Click the link for more information. and sea snakessea snake,
name for any of the venomous marine snakes of the family Hydrophidae, found in tropical waters of the Indian and Pacific oceans. The sea snake's body is flattened laterally and its oarlike tail is used as a scull.
..... Click the link for more information. , that have adopted an aquatic way of life; these may superficially resemble fishes and are sometimes erroneously called fishes, but they are air-breathers, and their anatomical structure reveals their relationship to land animals.
Characteristic Anatomical Features
A typical fish is torpedo-shaped, with a head containing a brain and sensory organs, a trunk with a muscular wall surrounding a cavity containing the internal organs, and a muscular post-anal tail. Most fish propel themselves through the water by weaving movements of their bodies and control their direction by means of the finsfin,
organ of locomotion characteristic of fish and consisting of thin tissue supported by cartilaginous or bony rays. In some fish, e.g., the eel, a single fin extends from the back, around the tail, and along the ventral surface.
..... Click the link for more information. . All have skins covered with slimy glandular secretions that decrease friction with the water; in addition, nearly all have scalesscale,
in zoology, an outgrowth, either bony or horny, of the skin of an animal. The major component of the scales of fishes is bone, and they are formed directly in the skin membrane as the fish grows.
..... Click the link for more information. , which together with the secretions form a nearly waterproof coating. All fishes have a lateral line system of sensory organs for detecting pressure changes in the water. All have water-breathing organs called gillsgills,
external respiratory organs of most aquatic animals. In fishes the gills are located in gill chambers at the rear of the mouth (pharynx). Water is taken in through the mouth, is forced through openings called gill slits, and then passes through the gill clefts, spaces
..... Click the link for more information. located in passages leading from the throat, or pharynx, to the exterior; a few fishes also have air-breathing lungs as an additional means of respiration. In all but the most primitive class, the gill passages are supported by skeletal structures called gill arches. Plankton-feeding fish have structures called gill rakers attached to the gill arches; these strain minute organisms from the water as it passes out of the pharynx. Fish breathe by taking water into the mouth and forcing it out through the gill passages; as the water passes over the thin-walled gills, dissolved oxygen diffuses into the gill capillaries and carbon dioxide diffuses out. The circulatory system is closed, and the heart is two-chambered; the blood is red. With few exceptions, fish are cold-blooded; that is, they cannot regulate their body temperature, which is the same as that of the environment.
Methods of reproduction are varied. Sharks have internal fertilization, and most give birth to live young. Those that lay eggs produce large ones with tough shells. Since embryonic development is well-protected in these fish, they produce a relatively small number of young, only seven or eight at a time in some species. A few of the bony fishes, including some aquarium species, are live bearers, but most lay small, unprotected eggs that are fertilized after deposition in water. In most marine species the eggs float freely in the currents, where they are eaten by other animals. An enormous number of eggs is therefore necessary to ensure the maturation of a few; in many species a female produces as many as 5 million eggs in one spawn. The eggs of most marine fishes contain oil droplets that buoy them up, while those of most freshwater fishes are heavy, with sticky surfaces that adhere to objects in the water. Most freshwater species build nests for the protection of the eggs, and in some the adults guard the nests.
Types of Fish
The Jawless Fishes
These primitive fishes lack jaws and the paired pelvic and pectoral fins characteristic of more advanced fishes. The two living types are the bloodsucking lampreys and the scavenging hagfisheshagfish,
primitive, jawless marine fish of the family Myxinidae, of worldwide distribution in cold and temperate waters. Its rudimentary skeleton, of cartilage rather than bone, has a braincase, but no jaw. The circular sucking mouth has rows of horny teeth.
..... Click the link for more information. . Fishes of the extinct class Placodermi, the armored fishes, were the first vertebrates to develop jaws and paired fins. These fish had bony skeletons and were covered with bony armor.
The Cartilaginous Fishes
The cartilaginous fish (sharksshark,
member of a group of almost exclusively marine and predaceous fishes. There are about 250 species of sharks, ranging from the 2-ft (60-cm) pygmy shark to 50-ft (15-m) giants. They are found in all seas, but are most abundant in warm waters.
..... Click the link for more information. , raysray,
extremely flat-bodied cartilaginous marine fish, related to the shark. The pectoral fins of most rays are developed into broad, flat, winglike appendages, attached all along the sides of the head; the animal swims by rippling movements of these wings.
..... Click the link for more information. , and chimaeraschimaera
, cartilaginous marine fish, related to the sharks. Also called ratfishes, chimaeras are found in temperate oceans throughout the world, mostly in deep water. They have large heads, long, thin, ratlike tails, and large, fanlike pectoral fins.
..... Click the link for more information. ) are distinguished from the bony fish by their cartilage skeletons, by the absence of either a swim bladderswim bladder,
large, thin-walled sac in some fishes that may function in several ways, e.g., as a buoyant float, a sound producer and receptor, and a respiratory organ. The swim bladder, or air bladder, is located in the dorsal portion of the body cavity and is filled with gases.
..... Click the link for more information. or lungs, by the construction of their tail fins, and by the absence in most of a gill covering, or operculum. The skin of members of this group is covered with imbedded toothlike structures called denticles, giving it a rough, sandpapery quality. Sharks are almost exclusively marine in distribution.
The Bony Fishes
The bony fishes are distinguished from other living fishes by their bone skeletons and by the presence of either a swim bladder (which functions as a float) or, in a few fishes, lungs. The bony fishes are divided into two subclasses, the lobe-finned (or fleshy-finned) fish and the ray-finned fish. The latter group includes over 95% of all living fish species.
The earliest bony fishes were fleshy-finned; they gave rise to the amphibians (the first terrestrial vertebrates, or tetrapods). The only surviving fleshy-finned fishes are the lungfisheslungfish,
common name for any of a group of fish belonging to the families Ceratodontidae, Lepidosirenidae, and Protopteridae, found in the rivers of Australia, South America, and Africa, respectively.
..... Click the link for more information. and coelacanths (see lobefinlobefin,
common name for any of a group of lunged, fleshy-finned, bony fishes, also called crossopterygians, that were dominant in the Devonian period and may have given rise to amphibians.
..... Click the link for more information. ). These fishes retain some of the traits of ancestral bony fishes: fleshy fins with supporting bones (precursors of the limbs of land vertebrates), internal nostrils, and lungs.
Ray-finned fishes, now predominant in both fresh and marine waters, represent an advanced adaptation of the bony fishes to strictly aquatic conditions; they are the most highly successful and diverse of the fishes. In nearly all of these fishes the lung has evolved into a hydrostatic organ, the swim bladder. The fins in this group consist of a web of skin supported by horny rays. Each ray is moved by a set of muscles, giving the fin great flexibility. Most ray-finned fish have overlapping scales made of very thin layers of bone. Their skeletal structure is light but strong and most have excellent vision.
See W. S. Hoar and D. J. Randall, Fish Physiology (6 vol., 1969–71); J. E. Webb et al. ed., Guide to Living Fishes (1981); J. A. Long, The Rise of Fishes (2d ed., 2010).
Fish,family long prominent in New York politics.
Nicholas Fish, 1758–1833, b. New York City. He studied law before serving ably as a major in a New York regiment throughout the American Revolution. A New York City alderman (1806–17), he was a leading Federalist and a close friend of Alexander Hamilton. He also served (1824–32) as chairman of the board of trustees of Columbia College, a post later held by his son, Hamilton Fish (1808–93), the most illustrious member of the clan (see separate articles for Hamilton FishFish, Hamilton,
1808–93, American statesman, b. New York City, grad. Columbia, 1827; son of Nicholas Fish (1758–1833). He studied law and was admitted to the bar in 1830.
..... Click the link for more information. , 1808–93, and for his youngest son, Stuyvesant FishFish, Stuyvesant
, 1851–1923, American railroad executive, b. New York City; son of Hamilton Fish (1808–93). He became (1877) a director of the Illinois Central RR, and as its president (1887–1907) he built the railroad into a large system.
..... Click the link for more information. ). Nicholas Fish, 1848–1902, b. New York City, was Hamilton's eldest son. He entered (1871) the U.S. diplomatic service and was minister to Belgium (1882–86).
A third son, Hamilton Fish, 1849–1936, b. Albany, N.Y., studied law and was admitted to the bar in 1873. He was a member of the New York state assembly (1874–96), serving as speaker in 1895–96, and was long Republican boss of Putnam co. On appointment by President Theodore Roosevelt, he was Assistant Treasurer of the United States in New York City (1903–8). He also served (1909–11) as a U.S. Representative.
The family's third Hamilton Fish, 1888–1991, son of the foregoing, b. Garrison, N.Y., was a football player at Harvard. A lawyer, Fish served in the New York state assembly (1914–16), distinguished himself in World War I as captain of an African-American infantry company, and from 1920 to 1945 was a U.S. Representative. A leading isolationist and vigorous anti-Communist, once accused of having connections with the Bundists and with other Axis supporters, he was opposed for renomination in 1944 by Gov. Thomas E. Dewey and other Republican leaders. Fish nevertheless won the primary but was defeated for reelection in November.
His son Hamilton Fish, 1926–96, b. Washington, D.C., continued the family's involvement in Republican politics. Admitted to the bar in 1957, he was elected to the U.S. House of Representatives from New York in 1968, where he consistently supported civil-rights legislation. He retired from Congress in 1995.
Fish(religion, spiritualism, and occult)
If used as an acrostic, the Greek letters spelling out the word "fish" can form the phrase "Jesus Christ, Son of God, Savior." For this reason the fish became an early Christian symbol. It was a natural match. Some of the apostles were fishermen. Jesus told them he would make them "fishers of men" (Matthew 4:19). He fed the multitudes with five small loaves of bread and a couple of (probably pickled) fish, the caterer for the occasion being a generous little boy (John 6). The disciples' first meal together after the resurrection featured a fish course (John 21).
A simple two-line drawing of a fish began to appear in out-of-the-way places, serving as a sort of Christian calling card and secret symbol. Its presence, to the initiated, meant, "Christian was here." Gradually the symbol worked its way into art and is still a popular motif on stained-glass windows, paintings, and bumper stickers.
Fish(religion, spiritualism, and occult)
The fish (or fishes) is a popular name for the sign Pisces.
an aquatic vertebrate that has inconstant body temperature, breathes by means of gills, and has nonpentadactyl limbs usually in the form of fins. There are two classes: Cyclostomata and Pisces.
The class Pisces includes seven subclasses: Acanthodii, Arthrodira, Pterichthyes, Elasmobranchii, Holocephali, Dipnoi, and Teleostomi. The first three subclasses comprise only fossil forms, whereas the remaining four include both fossil and extant forms. A number of paleontologists regard Pisces as a superclass, which they divide into seven classes. Some ichthyologists divide Pisces into two classes: Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes).
There are approximately 25,000 species of fishes, of which about 20,000 are extant. Approximately 1,400 species are encountered in the USSR.
Structure. The gills of fishes are of ectodermal origin, and the skeleton is bony or cartilaginous. In most Elasmobranchii and Acipenseridae an unsegmented notochord is retained. The vertebrae are biconcave (amphicoelous); only in the Lepisostei-formes are they biconvex (opisthocoelous). The vertebrae range in number from 16 (ocean sunfish) to more than 400 (oarfish). The skull of bony fishes consists of a large number of bones. The upper jaw usually articulates freely with the cranium (am-phistylic or hyostylic skull); only in a few fishes, for example, the Chimaeriformes and Dipnoi, is the upper jaw fused with the cranium (autostylic skull).
In most fishes the extremities are in the form of paired fins; some fishes lack extremities entirely. In some species the extremities are converted into suckers for attachment to a substrate (lumpsuckers, gobies, some catfishes) or into a copulatory organ (in males of Elasmobranchii and Phallostethoidei). Fishes also usually have unpaired dorsal and anal fins, which serve as stabilizers and, less commonly, as organs of locomotion (for example, the anal fin of the electric eel). In males of Cyprinodontiformes part of the anal fin serves as a copulatory organ. The caudal fin varies in shape: it may be homocercal, with asymmetry expressed only in the skeleton (in most bony fishes); diphycercal, with symmetry expressed both externally and internally (in Dipnoi); or heterocercal, with the skeleton penetrating the upper lobe of the fin (sharks and sturgeons). The caudal fin, as a rule, serves as a rudder and helps in producing forward motion.
The wavelike flexions of the body usually play a principal role in forward motion. Body shape varies greatly—it may be ribbonlike (oarfish, cutlass fish), snakelike (eels), spherical (some boxfishes), or greatly flattened (rays). Most fishes are spindle-shaped or have a slightly laterally compressed streamlined shape. All fishes have a symmetrical body; only adult flounders, which swim on their side, have both eyes on the same side of the head.
Fishes are covered with scales, spines, and bony plates, or they are naked (for example, the catfish). Scales may be placoid—in the form of cutaneous teeth (sharks and rays), ganoid—rhombic (fossil lungfishes and the longnose gar), cycloid—in the form of a thin smooth-edged plate (Salmonidae and Cyprinidae), or ctenoid—in the form of thin plates with spines on the outer edge (most Perciformes).
Many fishes have highly developed cutaneous gland cells that secrete mucus. In some deepwater fishes organs of illumination develop in the skin.
The coloration of fishes is very diverse. Species that inhabit open waters usually are bluish or greenish above; the abdomen and the sides are silvery. Fishes that dwell among thickets or rocks usually have transverse stripes or spots to make them less conspicuous. A black longitudinal stripe or a spot on the side of the body helps schooling fishes to keep the school intact. The coloration of a fish may change somewhat—for example, to blend in with the bottom over which it is swimming at a particular time.
Fishes have developed senses of olfaction, touch, hearing, and sight. There also are lateral line organs, which enable the animals to perceive water fluctuations. Vision in fishes is more short-focused than in terrestrial vertebrates. Fishes are able to distinguish colors in the water. In some deep-sea and cave fishes the eyes are reduced, but, at the same time, the other sense organs are highly developed. Fishes can perceive sounds, including those of infrasonic frequencies. They sometimes emit, especially during the mating period, clearly audible sounds by means of the swim bladder (some Sciaenidae) or by movement of the fins (Bagridae) or gill covers (some tropical Perciformes).
The brain is usually well developed. In Elasmobranchii the forebrain and cerebellum are particularly well developed, and the olfactory lobes are also very large. In most bony fishes the forebrain is small, whereas the midbrain and cerebellum are relatively large. There are no more than ten pairs of cranial nerves.
The principal organs of respiration in adult fishes are the gills. In larvae the circulatory network, which develops in the yolk sac and in the fin fold, serves for respiration. The larvae of Dipnoi and some other fishes have external gills. Many fishes that live under unfavorable conditions develop supplementary organs that serve for respiration of atmospheric air. Examples of such organs include the “lung” of dipnoans; the epibranchial organ in the snakehead, Macropodus, and anabas; and the pouchlike organ in the catfish Heteropneustes fossilis. The heart is bicameral. Only in the Dipnoi, which have “pulmonary” respiration, is the atrium partially divided by a septum.
In freshwater fishes and sharks the cavity fluids are hypertonic in relation to surrounding waters; hypertonicity is achieved by means of mineral salts and urea (sharks). Hypotonicity is characteristic of marine bony fishes. The kidneys are located beneath the spine, and in most species they are mesonephric. There is usually a separate stomach. Many fishes have special outgrowths known as pyloric limbs behind the stomach. A protuberance of the intestine forms the lungs of the Dipnoi and the swim bladder. In some fishes (Salmonidae, Cyprinidae), the swim bladder is joined by a duct to the intestine; in others (perches), it is not. The swim bladder is a hydrostatic organ, although in some fishes it has supplementary functions (respiratory organ, resonator). The digestive glands include the liver and the pancreas; the latter is sometimes part of the liver. The length of the intestine varies greatly. In sharks, sturgeons, and some other fishes the absorptive surface of the intestine is enlarged through the development of a fold, or spiral valve, in the duodenum. Most fishes have separate anal and urogenital openings. Sharks and the Dipnoi have a cloaca.
Fishes show a great diversity of size. The smallest fish is the goby Pandaka pygmaea, which measures 1 cm in length and which inhabits the Philippine Islands. The largest fish is the whale shark (Rhincodon typus), which reaches a length of 15 m.
Distribution. The richest fish life is encountered in the coastal waters of the western tropical zone of the Pacific Ocean. The region supports an abundance of perch, herring, eel, flounder, and other species. The fish life of the pelagic zone—that is, open waters far from land—includes herrings, anchovies, flying fishes, mackerels, swordfishes, sailfishes, tunas, and sharks. Deep-sea fish life is rather monotonous: it includes ancient deep-sea groups (Lophiidae, Myctophidae, Ceratioides, Macrouridae) and secondarily deep-sea groups (some Zoarcidae, Cottidae). Arctic and boreal waters are inhabited mainly by Cottidae, some flounders, Zoarcidae, Gadidae, and Osmeridae. Fishes of the superfamily Notothenioidei are most typical of antarctic waters, where they constitute more than 75 percent of the fish species.
Salmonidae are richly represented in arctic and boreal fresh-waters of Europe, Asia, and North America. Cyprinidae constitute a substantial part of the fish fauna in the temperate and low latitudes of Europe, Asia, Africa, and North America. The northern hemisphere has an abundance of sturgeons, Esoci-formes, and perches. North American freshwaters are characterized by longnose gars, the bowfin, sunfishes, and suckers. (Two species of suckers are found in East Asia.) The South American lungfish (one of the three extant Dipnoi genera) and electric eels are found only in the waters of South America. Also numerous in South America are characins, catfishes, and some perches. The following fishes are indigenous to African waters: dipnoan protopteruses, polypterids, Pantodontidae, and Mormyridae. Also numerous in Africa are characins, cyprinids, silurids, and some perches. The freshwaters of Australia are inhabited mainly by marine fishes that secondarily adapted to freshwater living; typical freshwater fishes are the Australian lungfish and Scleropages.
Reproduction. Most fishes deposit eggs (roe). A number of species are viviparous, including many sharks, cyprodonts (for example, the mosquito fish), the Baikal oil-fish, and the North Sea perch. Fertilization usually occurs in the water, but in fishes having a copulatory organ fertilization is internal. Fecundity varies from several eggs (some sharks and rays) to 300 million eggs (ocean sunfish). In most fishes the sexes are separate, but among some, such as sea perch, hermaphroditism occurs. Sexual dimorphism is often evident. The females are usually larger than the males, sometimes by several times (for example, in deep-sea Ceratioides). Only in those species in which the males participate in parental care (catfishes, Pseudogobio) are the females smaller than the males. Some fishes attain sexual maturity in the first year of life (mosquito fish, some gobies); others, such as the beluga, reach sexual maturity at 12 to 20 years. Most fishes reproduce several times in a lifetime. However, some deposit roe only once, dying shortly afterward (Far Eastern salmon).
Spawning may occur in the spring (roach, ide, pike, cod), summer (crucian carp, tench, Leucaspius delineatus), autumn (whitefish, European salmon), or winter (burbot, Eleginus). In some fishes all the eggs are deposited at the same time (sturgeons, whitefish, roach); other fishes are marked by fractional spawning. Some fishes lay their eggs in open waters, where they develop in a floating state (cod, almost all flounder, most herrings, mackerel, Amur silver carp, Pelecus cultratus). Many fishes produce sticky eggs, depositing them on plants (carp, crucian carp) or rocks (gobies, vimba). Some species dig nests in the bottom (dog salmon, pink salmon).
The eggs vary in structure as a result of conditions of development. Eggs that develop under conditions unfavorable for respiration are usually brightly colored, owing to the formation of “respiratory” carotenoid pigments. Pelagic eggs, that is, those that swim in open waters, usually have a greatly enlarged membrane or perivitelline space to ensure better flotation. Many fishes protect their eggs. The incubation period lasts from several hours (many tropical fishes) to three or four months (some Salmonidae). The larvae, which usually have a yolk sac when they hatch, feed on the yolk reserves in the first days of life.
Fishes grow throughout their entire lives. As a result of uneven growth, the scales and bones develop annual layers, from which the age of a fish may be determined. The longevity of fishes is from one (some gobies) to 100 years (beluga).
Feeding habits. Fishes feed on a variety of substances. The young of most species feed on small planktonic organisms, protozoans, rotifers, and crustaceans. Adult fishes include both predators and fishes that feed on. benthic invertebrates (benthos), pelagic invertebrates (plankton), and plants. There are parasitic fishes: for example, the American catfish Stegophilus parasitizes other fishes, and some fierasfers are parasites of invertebrates.
The feeding habits of a fish are often related to the animal’s structure and behavior. Predators generally have strong teeth, a large stomach, and a short intestine. Some chase their prey (salmon, pike perch, barracuda), others lie in wait and ambush their prey (pike perch, Cottidae), and others lure and seize their prey (angler). Most predators orient themselves mainly by means of vision; usually their perception of water fluctuations is also well developed.
Fishes that serve as prey for other fishes develop various defensive adaptations, such as spines on the fins (ruff, stickleback) or on the gill covers (ocean perch, Cottidae). Some fishes have poison glands at the base of their spines. Among the fishes that inhabit the waters of the USSR, the lesser weever (Trachinus vipera) has the most toxic secretions. The venom of the stone-fish, which inhabits waters of the Malay Archipelago, may be lethal to man.
Fishes that feed on benthic invertebrates (wolffish, wrasses, rays, roach, bream) have powerful maxillary or pharyngeal teeth, which are adapted for crushing hard shells and carapaces. Many bottom-feeding fishes (carp, bream, tench, mullet) dig for food, sometimes to depths of 10–15 cm. They locate food by means of their tactile organs and external taste organs. Some fish species have taste buds on the ends of the snout, on the rays of the pectoral fins, on the antennae, or on some other part of the body. Fishes that feed on plankton usually have adaptations for filtering, such as long gill rakers. Such fishes find food with their organs of sight or with their lateral line organs (herrings, sardines, anchovies). Herbivorous fishes have very long intestines and poorly developed stomachs. Often the lower lip is pointed and adapted for scraping vegetation off a substrate (Chondrostoma, Varicorhinus). Some fishes feed throughout the year, but in most species feeding ceases during reproduction and wintering. Some fishes feed most intensively in the summer (most cyprinids, pike perch, catfish), and others in the winter (burbot, whitefish, muksun, Ob’ whitefish). Fishes that detect food by sight feed in sunlit waters; those that feed by touch and taste eat in darkness.
Migration. Many fishes do not make distant journeys but live permanently in the same region. However, some make considerable migrations (seeMIGRATION, ANIMAL). Migratory fishes enter rivers from the sea or seas from rivers for spawning.
Wintering. Although wintering far from characterizes all fishes, fishes in many temperate latitudes experience a sharp decrease in activity, a slowing down of metabolism, and cessation of feeding during the winter. Fishes often gather in large schools for wintering. Some tropical fishes aestivate during drought (Protopterus).
Fossils. Fossil fishes evidently appeared in freshwaters during the Silurian and in seas during the Devonian. Silurian deposits are characterized by ancient cyclostomes. The Devonian experienced the flowering and extinction of Ostracodermi and the appearance of the class Pisces. The majority of extant groups of fishes appeared in the Cretaceous period.
Significance. Fishes are of great value to man. The flesh of most species is used as food, as is the roe of many. The skin of some fishes is used in the manufacture of various articles. Fat melted down from the liver and other internal organs of some species, such as cod, is rich in vitamins; it is used for medicinal and industrial purposes. Feed meal and fertilizers are manufactured from fishes.
In some regions certain species of fishes (mosquito fish) are beneficial, since they eat the larvae of mosquitoes that are carriers of malaria. Herbivorous fishes are used to purify bodies of water (canals, ponds).
Fish culture is widespread. To increase fish production it is necessary to keep toxic substances out of the water. Reproduction of fish reserves must be ensured during the construction of hydroengineering structures. The exploitation of fish must be pursued in a rational manner, and a complex of conservation measures must be taken. In seas and inland bodies of water, it is necessary to implement measures to intensify the reproductive process. A number of carp breeds have been developed by selection. Many fish species are raised in aquariums to complement interior decors.
The flesh, skin, and roe of some fishes are poisonous. The insufficiently cooked roe of Schizothorax are poisonous.
The branch of zoology that deals with fishes is called ichthyology.
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Berg, L. S. Sistema ryboobraznykh i ryb nyne zhivushchikh i iskopaemykh, 2nd ed. Moscow-Leningrad, 1955. (Trudy Zoologicheskogo instituta AN SSSR, vol. 20.)
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Lindberg, G. U. Opredelitel’ i kharakteristika semeistv ryb mirovoi fauny. Leningrad, 1971.
Zhizn’ zhivotnykh, vol. 4, part 1. Moscow, 1971.
Nikol’skii, G. V. Chastnaia ikhtiologiia, 3rd ed. Moscow, 1971.
Nikol’skii, G. V. Ekologiia ryb, 3rd ed. Moscow, 1974.
Stroganov, N. S. Ekologicheskaiafiziologiia ryb, vol. 1. Moscow, 1962.
Normann, J. R. A History of Fishes. London, 1963.
Moy-Thomas, J. A. Palaeozoic Fishes, 2nd ed. London, 1971.
Cărăusu, S. I. Tratat de ichtiologie. [Bucharest] 1952.
Lagler, K. F., J. E. Bardach, and R. R. Miller. Ichthyology. New York, 1962.
Marshall, N. B. The Life of Fishes. London, 1965.
Fish Physiology, vols. 1–6. Edited by W. S. Hoar and D. J. Randall. New York-London, 1969–71.
G. V. NIKOL’SKII
What does it mean when you dream about fish?
Large bodies of water often symbolize the unconscious, so any sea creature can represent a message from the unconscious or “diving” into the unconscious. Completely at home in the ocean, fish are the best-equipped creatures for exploring its depths, and are thus positive symbols for anyone engaged in therapy or self transformation. The activity of fishing can indicate a quest, particularly for nourishment, and it can indicate an exploration of the unconscious. Fish can also be sexual symbols and, because of their association with Christianity, can be Christ symbols.
FISH[fish or ¦ef¦ī¦es′āch]