FishFossil range: Mid Cambrian–Recent

Giant grouper swimming among schools of

other fish

Head-on view of a red lionfish

Scientific classification

Kingdom: Animalia

Phylum: Chordata

(unranked) Craniata

Included groups

Jawless fish†Armoured fishCartilaginous fishRay-finned fish

FishFrom Wikipedia, the free encyclopedia

A fish is any member of a paraphyletic group of organismsthat consist of all gill-bearing aquatic craniate animals that lacklimbs with digits. Included in this definition are the livinghagfish, lampreys, and cartilaginous and bony fish, as well asvarious extinct related groups. Most fish are ectothermic("cold-blooded"), allowing their body temperatures to vary asambient temperatures change, though some of the large activeswimmers like white shark and tuna can hold a higher coretemperature.[1][2] Fish are abundant in most bodies of water.They can be found in nearly all aquatic environments, fromhigh mountain streams (e.g., char and gudgeon) to the abyssaland even hadal depths of the deepest oceans (e.g., gulpers andanglerfish). At 32,000 species, fish exhibit greater speciesdiversity than any other group of vertebrates.[3]

Fish are an important resource for humans worldwide,especially as food. Commercial and subsistence fishers huntfish in wild fisheries (see fishing) or farm them in ponds or incages in the ocean (see aquaculture). They are also caught byrecreational fishers, kept as pets, raised by fishkeepers, andexhibited in public aquaria. Fish have had a role in culturethrough the ages, serving as deities, religious symbols, and asthe subjects of art, books and movies.

Because the term "fish" is defined negatively, and excludesthe tetrapods (i.e., the amphibians, reptiles, birds andmammals) which descend from within the same ancestry, it isparaphyletic, and is not considered a proper grouping insystematic biology. The traditional term pisces (also ichthyes)is considered a typological, but not a phylogeneticclassification.

The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrianperiod. Although they lacked a true spine, they possessednotochords which allowed them to be more agile than theirinvertebrate counterparts. Fish would continue to evolvethrough the Paleozoic era, diversifying into a wide variety offorms. Many fish of the Paleozoic developed external armorthat protected them from predators. The first fish with jawsappeared in the Silurian period, after which many (such assharks) became formidable marine predators rather than justthe prey of arthropods.

Contents

PreЄ Є O S D C P T J K PgN

Lobe-finned fishes

Excluded groups

Tetrapods

1 Evolution1.1 Taxonomy

2 Diversity3 Anatomy

3.1 Respiration3.1.1 Gills3.1.2 Air breathing

3.2 Circulation3.3 Digestion3.4 Excretion3.5 Scales3.6 Sensory and nervous system

3.6.1 Central nervous system3.6.2 Sense organs

3.6.2.1 Vision3.6.2.2 Hearing

3.6.3 Capacity for pain3.7 Muscular system3.8 Homeothermy3.9 Reproductive system

4 Diseases4.1 Immune system

5 Conservation5.1 Overfishing5.2 Habitat destruction5.3 Exotic species

6 Importance to humans6.1 Aquarium collecting6.2 Economic importance6.3 Recreation6.4 Culture

7 Terminology7.1 Shoal or school7.2 Fish or fishes

8 See also9 Notes10 References11 Further reading12 External links

EvolutionMain article: evolution of fish

Fish do not represent a monophyletic group, and therefore the "evolution of fish" is not studied as a singleevent.[5]

Early fish from the fossil record are represented by a group of small, jawless, armored fish known asOstracoderms. Jawless fish lineages are mostly extinct. An extant clade, the Lampreys may approximateancient pre-jawed fish. The first jaws are found in Placodermi fossils. The diversity of jawed vertebratesmay indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is

Outdated evolutionary view ofcontinual gradation (click to animate)

Dunkleosteus was a gigantic, 10 meter(33 feet) long prehistoric fish.

greater biting force, improved respiration, or a combination of factors.

Fish may have evolved from a creature similar to a coral-like Sea squirt, whose larvae resemble primitivefish in important ways. The first ancestors of fish may have kept the larval form into adulthood (as somesea squirts do today), although perhaps the reverse is the case.

Taxonomy

Fish are a paraphyletic group: that is, any clade containing all fishalso contains the tetrapods, which are not fish. For this reason,groups such as the "Class Pisces" seen in older reference worksare no longer used in formal classifications.

Traditional classification divide fish into three extant classes, andwith extinct forms sometimes classified within the tree, sometimesas their own classes:[6][7]

Class Agnatha (jawless fish)Subclass Cyclostomata (hagfish and lampreys)Subclass Ostracodermi (armoured jawless fish) †

Class Chondrichthyes (cartilaginous fish)Subclass Elasmobranchii (sharks and rays)Subclass Holocephali (chimaeras and extinctrelatives)

Class Placodermi (armoured fish) †Class Acanthodii ("spiny sharks", sometimes classifiedunder bony fishes)†Class Osteichthyes (bony fish)

Subclass Actinopterygii (ray finned fishes)Subclass Sarcopterygii (fleshy finned fishes, ancestorsof tetrapods)

The above scheme is the one most commonly encountered in non-specialist and general works. Many of the above groups are paraphyletic, in that they have given rise tosuccessive groups: Agnathans are ancestral to Chondrichthyes, who again have given rise toAcanthodiians, the ancestors of Osteichthyes. With the arrival of phylogenetic nomenclature, the fishes hasbeen split up into a more detailed scheme, with the following major groups:

Class Myxini (hagfish)Class Pteraspidomorphi † (early jawless fish)Class Thelodonti †Class Anaspida †Class Petromyzontida or Hyperoartia

Petromyzontidae (lampreys)Class Conodonta (conodonts) †Class Cephalaspidomorphi † (early jawless fish)

(unranked) Galeaspida †(unranked) Pituriaspida †(unranked) Osteostraci †

Infraphylum Gnathostomata (jawed vertebrates)Class Placodermi † (armoured fish)Class Chondrichthyes (cartilaginous fish)

Fish come in many shapes and sizes.This is a sea dragon, a close relativeof the seahorse. Their leaf-likeappendages enable them to blend inwith floating seaweed.

Class Acanthodii † (spiny sharks)Superclass Osteichthyes (bony fish)

Class Actinopterygii (ray-finned fish)Subclass Chondrostei

Order Acipenseriformes (sturgeons and paddlefishes)Order Polypteriformes (reedfishes and bichirs).

Subclass NeopterygiiInfraclass Holostei (gars and bowfins)Infraclass Teleostei (many orders of common fish)

Class Sarcopterygii (lobe-finned fish)Subclass Actinistia (coelacanths)Subclass Dipnoi (lungfish)

† – indicates extinct taxonSome palaeontologists contend that because Conodonta are chordates, they are primitive fish. For a fullertreatment of this taxonomy, see the vertebrate article.

The position of hagfish in the phylum chordata is not settled. Phylogenetic research in 1998 and 1999supported the idea that the hagfish and the lampreys form a natural group, the Cyclostomata, that is a sistergroup of the Gnathostomata.[8][9]

The various fish groups account for more than half of vertebrate species. There are almost 28,000 knownextant species, of which almost 27,000 are bony fish, with 970 sharks, rays, and chimeras and about 108hagfish and lampreys.[10] A third of these species fall within the nine largest families; from largest tosmallest, these families are Cyprinidae, Gobiidae, Cichlidae, Characidae, Loricariidae, Balitoridae,Serranidae, Labridae, and Scorpaenidae. About 64 families are monotypic, containing only one species.The final total of extant species may grow to exceed 32,500.[11]

DiversityMain article: Diversity of fish

The term "fish" most precisely describes any non-tetrapod craniate(i.e. an animal with a skull and in most cases a backbone) that hasgills throughout life and whose limbs, if any, are in the shape offins.[12] Unlike groupings such as birds or mammals, fish are not asingle clade but a paraphyletic collection of taxa, includinghagfishes, lampreys, sharks and rays, ray-finned fish, coelacanths,and lungfish.[13][14] Indeed, lungfish and coelacanths are closerrelatives of tetrapods (such as mammals, birds, amphibians, etc.)than of other fish such as ray-finned fish or sharks, so the lastcommon ancestor of all fish is also an ancestor to tetrapods. Asparaphyletic groups are no longer recognised in modern systematicbiology, the use of the term "fish" as a biological group must beavoided.

Many types of aquatic animals commonly referred to as "fish" are not fish in the sense given above;examples include shellfish, cuttlefish, starfish, crayfish and jellyfish. In earlier times, even biologists did notmake a distinction – sixteenth century natural historians classified also seals, whales, amphibians,crocodiles, even hippopotamuses, as well as a host of aquatic invertebrates, as fish.[15] However,

according the definition above, all mammals, including cetaceans like whales and dolphins, are not fish. Insome contexts, especially in aquaculture, the true fish are referred to as finfish (or fin fish) to distinguishthem from these other animals.

A typical fish is ectothermic, has a streamlined body for rapid swimming, extracts oxygen from waterusing gills or uses an accessory breathing organ to breathe atmospheric oxygen, has two sets of paired fins,usually one or two (rarely three) dorsal fins, an anal fin, and a tail fin, has jaws, has skin that is usuallycovered with scales, and lays eggs.

Each criterion has exceptions. Tuna, swordfish, and some species of sharks show some warm-bloodedadaptations—they can heat their bodies significantly above ambient water temperature.[13] Streamliningand swimming performance varies from fish such as tuna, salmon, and jacks that can cover 10–20 body-lengths per second to species such as eels and rays that swim no more than 0.5 body-lengths persecond.[13] Many groups of freshwater fish extract oxygen from the air as well as from the water using avariety of different structures. Lungfish have paired lungs similar to those of tetrapods, gouramis have astructure called the labyrinth organ that performs a similar function, while many catfish, such as Corydorasextract oxygen via the intestine or stomach.[16] Body shape and the arrangement of the fins is highlyvariable, covering such seemingly un-fishlike forms as seahorses, pufferfish, anglerfish, and gulpers.Similarly, the surface of the skin may be naked (as in moray eels), or covered with scales of a variety ofdifferent types usually defined as placoid (typical of sharks and rays), cosmoid (fossil lungfish andcoelacanths), ganoid (various fossil fish but also living gars and bichirs), cycloid, and ctenoid (these lasttwo are found on most bony fish).[17] There are even fish that live mostly on land. Mudskippers feed andinteract with one another on mudflats and go underwater to hide in their burrows.[18] The catfishPhreatobius cisternarum lives in underground, phreatic habitats, and a relative lives in waterlogged leaflitter.[19][20]

Fish range in size from the huge 16-metre (52 ft) whale shark to the tiny 8-millimetre (0.3 in) stoutinfantfish.

Fish species diversity is roughly divided equally between marine (oceanic) and freshwater ecosystems.Coral reefs in the Indo-Pacific constitute the center of diversity for marine fishes, whereas continentalfreshwater fishes are most diverse in large river basins of tropical rainforests, especially the Amazon,Congo, and Mekong basins. More than 5,600 fish species inhabit Neotropical freshwaters alone, such thatNeotropical fishes represent about 10% of all vertebrate species on the Earth. Exceptionally rich sites in theAmazon basin, such as Cantão State Park, can contain more freshwater fish species than occur in all ofEurope.[21]

AnatomyMain article: Fish anatomy

Respiration

Gills

Most fish exchange gases using gills on either side of the pharynx. Gills consist of threadlike structurescalled filaments. Each filament contains a capillary network that provides a large surface area forexchanging oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water through theirmouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the

The anatomy of Lampanyctodes hectoris(1) – operculum (gill cover), (2) – lateral line, (3) – dorsalfin, (4) – fat fin, (5) – caudal peduncle, (6) – caudal fin, (7)– anal fin, (8) – photophores, (9) – pelvic fins (paired), (10)– pectoral fins (paired)

water, causing countercurrent exchange. Thegills push the oxygen-poor water out throughopenings in the sides of the pharynx. Somefish, like sharks and lampreys, possessmultiple gill openings. However, bony fishhave a single gill opening on each side. Thisopening is hidden beneath a protective bonycover called an operculum.

Juvenile bichirs have external gills, a veryprimitive feature that they share with larvalamphibians.

Air breathing

Fish from multiple groups can live out of the water for extended time periods. Amphibious fish such as themudskipper can live and move about on land for up to several days, or live in stagnant or otherwiseoxygen depleted water. Many such fish can breathe air via a variety of mechanisms. The skin of anguillideels may absorb oxygen directly. The buccal cavity of the electric eel may breathe air. Catfish of thefamilies Loricariidae, Callichthyidae, and Scoloplacidae absorb air through their digestive tracts.[22]

Lungfish, with the exception of the Australian lungfish, and bichirs have paired lungs similar to those oftetrapods and must surface to gulp fresh air through the mouth and pass spent air out through the gills. Garand bowfin have a vascularized swim bladder that functions in the same way. Loaches, trahiras, and manycatfish breathe by passing air through the gut. Mudskippers breathe by absorbing oxygen across the skin(similar to frogs). A number of fish have evolved so-called accessory breathing organs that extractoxygen from the air. Labyrinth fish (such as gouramis and bettas) have a labyrinth organ above the gillsthat performs this function. A few other fish have structures resembling labyrinth organs in form andfunction, most notably snakeheads, pikeheads, and the Clariidae catfish family.

Breathing air is primarily of use to fish that inhabit shallow, seasonally variable waters where the water'soxygen concentration may seasonally decline. Fish dependent solely on dissolved oxygen, such as perchand cichlids, quickly suffocate, while air-breathers survive for much longer, in some cases in water that islittle more than wet mud. At the most extreme, some air-breathing fish are able to survive in damp burrowsfor weeks without water, entering a state of aestivation (summertime hibernation) until water returns.

Air breathing fish can be divided into obligate air breathers and facultative air breathers. Obligate airbreathers, such as the African lungfish, must breathe air periodically or they suffocate. Facultative airbreathers, such as the catfish Hypostomus plecostomus, only breathe air if they need to and will otherwiserely on their gills for oxygen. Most air breathing fish are facultative air breathers that avoid the energeticcost of rising to the surface and the fitness cost of exposure to surface predators.[22]

Circulation

Fish have a closed-loop circulatory system. The heart pumps the blood in a single loop throughout thebody. In most fish, the heart consists of four parts, including two chambers and an entrance and exit.[23]

The first part is the sinus venosus, a thin-walled sac that collects blood from the fish's veins beforeallowing it to flow to the second part, the atrium, which is a large muscular chamber. The atrium serves asa one-way antechamber, sends blood to the third part, ventricle. The ventricle is another thick-walled,muscular chamber and it pumps the blood, first to the fourth part, bulbus arteriosus, a large tube, and thenout of the heart. The bulbus arteriosus connects to the aorta, through which blood flows to the gills for

Tuna gills inside of the head. The fish head isoriented snout-downwards, with the view lookingtowards the mouth.

oxygenation.

Digestion

Jaws allow fish to eat a wide variety of food,including plants and other organisms. Fish ingest foodthrough the mouth and break it down in theesophagus. In the stomach, food is further digestedand, in many fish, processed in finger-shapedpouches called pyloric caeca, which secrete digestiveenzymes and absorb nutrients. Organs such as theliver and pancreas add enzymes and variouschemicals as the food moves through the digestivetract. The intestine completes the process of digestionand nutrient absorption.

Excretion

As with many aquatic animals, most fish release theirnitrogenous wastes as ammonia. Some of the wastes diffuse through the gills. Blood wastes are filtered bythe kidneys.

Saltwater fish tend to lose water because of osmosis. Their kidneys return water to the body. The reversehappens in freshwater fish: they tend to gain water osmotically. Their kidneys produce dilute urine forexcretion. Some fish have specially adapted kidneys that vary in function, allowing them to move fromfreshwater to saltwater.

Scales

Main article: Fish scale

The scales of fish originate from the mesoderm (skin); they may be similar in structure to teeth.

Sensory and nervous system

Central nervous system

Fish typically have quite small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal.[24] However, some fish have relatively largebrains, most notably mormyrids and sharks, which have brains about as massive relative to body weight asbirds and marsupials.[25]

Fish brains are divided into several regions. At the front are the olfactory lobes, a pair of structures thatreceive and process signals from the nostrils via the two olfactory nerves.[24] The olfactory lobes are verylarge in fish that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes isthe two-lobed telencephalon, the structural equivalent to the cerebrum in higher vertebrates. In fish thetelencephalon is concerned mostly with olfaction.[24] Together these structures form the forebrain.

Dorsal view of the brain ofthe rainbow trout

Connecting the forebrain to the midbrain is the diencephalon (in the diagram, this structure is below theoptic lobes and consequently not visible). The diencephalon performs functions associated with hormonesand homeostasis.[24] The pineal body lies just above the diencephalon. This structure detects light,maintains circadian rhythms, and controls color changes.[24]

The midbrain or mesencephalon contains the two optic lobes. These are very large in species that hunt bysight, such as rainbow trout and cichlids.[24]

The hindbrain or metencephalon is particularly involved in swimming and balance.[24] The cerebellum isa single-lobed structure that is typically the biggest part of the brain.[24] Hagfish and lampreys haverelatively small cerebellae, while the mormyrid cerebellum is massive and apparently involved in theirelectrical sense.[24]

The brain stem or myelencephalon is the brain's posterior.[24] As well as controlling some muscles andbody organs, in bony fish at least, the brain stem governs respiration andosmoregulation.[24]

Sense organs

Most fish possess highly developed sense organs. Nearly all daylight fishhave color vision that is at least as good as a human's (see vision in fishes).Many fish also have chemoreceptors that are responsible for extraordinarysenses of taste and smell. Although they have ears, many fish may nothear very well. Most fish have sensitive receptors that form the lateral linesystem, which detects gentle currents and vibrations, and senses themotion of nearby fish and prey.[26] Some fish, such as catfish and sharks,have organs that detect weak electric currents on the order of millivolt.[27]

Other fish, like the South American electric fishes Gymnotiformes, canproduce weak electric currents, which they use in navigation and socialcommunication.

Fish orient themselves using landmarks and may use mental maps basedon multiple landmarks or symbols. Fish behavior in mazes reveals thatthey possess spatial memory and visual discrimination.[28]

Vision

Main article: Vision in fishes

Vision is an important sensory system for most species of fish. Fish eyes are similar to those of terrestrialvertebrates like birds and mammals, but have a more spherical lens. Their retinas generally have both rodcells and cone cells (for scotopic and photopic vision), and most species have colour vision. Some fish cansee ultraviolet and some can see polarized light. Amongst jawless fish, the lamprey has well-developedeyes, while the hagfish has only primitive eyespots.[29] Fish vision shows adaptation to their visualenvironment, for example deep sea fishes have eyes suited to the dark environment.

Hearing

Main article: Hearing in fishes

Swim bladder of a Rudd (Scardiniuserythrophthalmus)

Hearing is an important sensory system for most species of fish. Fish sense sound using their lateral linesand their ears.

Capacity for pain

Further information: Pain in fish

Experiments done by William Tavolga provide evidence that fish have pain and fear responses. Forinstance, in Tavolga’s experiments, toadfish grunted when electrically shocked and over time they came togrunt at the mere sight of an electrode.[30]

In 2003, Scottish scientists at the University of Edinburgh and the Roslin Institute concluded that rainbowtrout exhibit behaviors often associated with pain in other animals. Bee venom and acetic acid injected intothe lips resulted in fish rocking their bodies and rubbing their lips along the sides and floors of their tanks,which the researchers concluded were attempts to relieve pain, similar to what mammals woulddo.[31][32][33] Neurons fired in a pattern resembling human neuronal patterns.[33]

Professor James D. Rose of the University of Wyoming claimed the study was flawed since it did notprovide proof that fish possess "conscious awareness, particularly a kind of awareness that is meaningfullylike ours".[34] Rose argues that since fish brains are so different from human brains, fish are probably notconscious in the manner humans are, so that reactions similar to human reactions to pain instead have othercauses. Rose had published a study a year earlier arguing that fish cannot feel pain because their brainslack a neocortex.[35] However, animal behaviorist Temple Grandin argues that fish could still haveconsciousness without a neocortex because "different species can use different brain structures and systemsto handle the same functions."[33]

Animal welfare advocates raise concerns about the possible suffering of fish caused by angling. Somecountries, such as Germany have banned specific types of fishing, and the British RSPCA now formallyprosecutes individuals who are cruel to fish.[36]

Muscular system

Main article: Fish locomotion

Most fish move by alternately contracting paired sets of muscleson either side of the backbone. These contractions form S-shapedcurves that move down the body. As each curve reaches the backfin, backward force is applied to the water, and in conjunctionwith the fins, moves the fish forward. The fish's fins function likean airplane's flaps. Fins also increase the tail's surface area,increasing speed. The streamlined body of the fish decreases theamount of friction from the water. Since body tissue is denser than water, fish must compensate for thedifference or they will sink. Many bony fish have an internal organ called a swim bladder that adjusts theirbuoyancy through manipulation of gases.

Homeothermy

Although most fish are exclusively ectothermic, there are exceptions.

A great white shark off IslaGuadalupe

Organs: 1. Liver, 2. Gas bladder, 3.Roe, 4. Pyloric caeca, 5. Stomach, 6.Intestine

Certain species of fish maintain elevated body temperatures. Endothermic teleosts (bony fish) are all in thesuborder Scombroidei and include the billfishes, tunas, and one species of "primitive" mackerel(Gasterochisma melampus). All sharks in the family Lamnidae – shortfin mako, long fin mako, white,porbeagle, and salmon shark – are endothermic, and evidence suggests the trait exists in family Alopiidae(thresher sharks). The degree of endothermy varies from the billfish, which warm only their eyes and

brain, to bluefin tuna and porbeagle sharks who maintain bodytemperatures elevated in excess of 20 °C above ambient watertemperatures.[37] See also gigantothermy. Endothermy, thoughmetabolically costly, is thought to provide advantages such asincreased muscle strength, higher rates of central nervous systemprocessing, and higher rates of digestion.

Reproductive system

Further information: Spawn (biology)

Fish reproductive organs include testes and ovaries. In mostspecies, gonads are paired organs of similar size, which can bepartially or totally fused.[38] There may also be a range ofsecondary organs that increase reproductive fitness.

In terms of spermatogonia distribution, the structure of teleoststestes has two types: in the most common, spermatogonia occur allalong the seminiferous tubules, while in Atherinomorph fish theyare confined to the distal portion of these structures. Fish canpresent cystic or semi-cystic spermatogenesis in relation to therelease phase of germ cells in cysts to the seminiferous tubuleslumen.[38]

Fish ovaries may be of three types: gymnovarian, secondarygymnovarian or cystovarian. In the first type, the oocytes are released directly into the coelomic cavity andthen enter the ostium, then through the oviduct and are eliminated. Secondary gymnovarian ovaries shedova into the coelom from which they go directly into the oviduct. In the third type, the oocytes areconveyed to the exterior through the oviduct.[39] Gymnovaries are the primitive condition found inlungfish, sturgeon, and bowfin. Cystovaries characterize most teleosts, where the ovary lumen hascontinuity with the oviduct.[38] Secondary gymnovaries are found in salmonids and a few other teleosts.

Oogonia development in teleosts fish varies according to the group, and the determination of oogenesisdynamics allows the understanding of maturation and fertilization processes. Changes in the nucleus,ooplasm, and the surrounding layers characterize the oocyte maturation process.[38]

Postovulatory follicles are structures formed after oocyte release; they do not have endocrine function,present a wide irregular lumen, and are rapidly reabsorbed in a process involving the apoptosis of follicularcells. A degenerative process called follicular atresia reabsorbs vitellogenic oocytes not spawned. This

An example of zooplankton

process can also occur, but less frequently, in oocytes in other development stages.[38]

Some fish, like the California sheephead, are hermaphrodites, having both testes and ovaries either atdifferent phases in their life cycle or, as in hamlets, have them simultaneously.

Over 97% of all known fish are oviparous,[40] that is, the eggs develop outside the mother's body.Examples of oviparous fish include salmon, goldfish, cichlids, tuna, and eels. In the majority of thesespecies, fertilisation takes place outside the mother's body, with the male and female fish shedding theirgametes into the surrounding water. However, a few oviparous fish practice internal fertilization, with themale using some sort of intromittent organ to deliver sperm into the genital opening of the female, mostnotably the oviparous sharks, such as the horn shark, and oviparous rays, such as skates. In these cases, themale is equipped with a pair of modified pelvic fins known as claspers.

Marine fish can produce high numbers of eggs which are often released into the open water column. Theeggs have an average diameter of 1 millimetre (0.039 in).

Egg of lamprey

Egg of catshark(mermaids' purse)

Egg of bullhead shark

Egg of chimaera

The newly hatched young of oviparous fish are called larvae.They are usually poorly formed, carry a large yolk sac (fornourishment) and are very different in appearance from juvenileand adult specimens. The larval period in oviparous fish isrelatively short (usually only several weeks), and larvae rapidlygrow and change appearance and structure (a process termedmetamorphosis) to become juveniles. During this transition larvaemust switch from their yolk sac to feeding on zooplankton prey, aprocess which depends on typically inadequate zooplanktondensity, starving many larvae.

In ovoviviparous fish the eggs develop inside the mother's bodyafter internal fertilization but receive little or no nourishment directly from the mother, depending insteadon the yolk. Each embryo develops in its own egg. Familiar examples of ovoviviparous fish includeguppies, angel sharks, and coelacanths.

Some species of fish are viviparous. In such species the mother retains the eggs and nourishes the embryos.Typically, viviparous fish have a structure analogous to the placenta seen in mammals connecting themother's blood supply with that of the embryo. Examples of viviparous fish include the surf-perches,splitfins, and lemon shark. Some viviparous fish exhibit oophagy, in which the developing embryos eatother eggs produced by the mother. This has been observed primarily among sharks, such as the shortfinmako and porbeagle, but is known for a few bony fish as well, such as the halfbeak Nomorhamphus

ebrardtii.[41] Intrauterine cannibalism is an even more unusual mode of vivipary, in which the largestembryos eat weaker and smaller siblings. This behavior is also most commonly found among sharks, suchas the grey nurse shark, but has also been reported for Nomorhamphus ebrardtii.[41]

Aquarists commonly refer to ovoviviparous and viviparous fish as livebearers.

DiseasesMain article: Fish diseases and parasites

Like other animals, fish suffer from diseases and parasites. To prevent disease they have a variety ofdefenses. Non-specific defenses include the skin and scales, as well as the mucus layer secreted by theepidermis that traps and inhibits the growth of microorganisms. If pathogens breach these defenses, fishcan develop an inflammatory response that increases blood flow to the infected region and delivers whiteblood cells that attempt to destroy pathogens. Specific defenses respond to particular pathogens recognisedby the fish's body, i.e., an immune response.[42] In recent years, vaccines have become widely used inaquaculture and also with ornamental fish, for example furunculosis vaccines in farmed salmon and koiherpes virus in koi.[43][44]

Some species use cleaner fish to remove external parasites. The best known of these are the Bluestreakcleaner wrasses of the genus Labroides found on coral reefs in the Indian and Pacific Oceans. These smallfish maintain so-called "cleaning stations" where other fish congregate and perform specific movements toattract the attention of the cleaners.[45] Cleaning behaviors have been observed in a number of fish groups,including an interesting case between two cichlids of the same genus, Etroplus maculatus, the cleaner, andthe much larger Etroplus suratensis.[46]

Immune system

Immune organs vary by type of fish.[47] In the jawless fish (lampreys and hagfish), true lymphoid organsare absent. These fish rely on regions of lymphoid tissue within other organs to produce immune cells. Forexample, erythrocytes, macrophages and plasma cells are produced in the anterior kidney (or pronephros)and some areas of the gut (where granulocytes mature.) They resemble primitive bone marrow in hagfish.Cartilaginous fish (sharks and rays) have a more advanced immune system. They have three specializedorgans that are unique to chondrichthyes; the epigonal organs (lymphoid tissue similar to mammalian bone)that surround the gonads, the Leydig's organ within the walls of their esophagus, and a spiral valve in theirintestine. These organs house typical immune cells (granulocytes, lymphocytes and plasma cells). Theyalso possess an identifiable thymus and a well-developed spleen (their most important immune organ)where various lymphocytes, plasma cells and macrophages develop and are stored. Chondrostean fish(sturgeons, paddlefish and bichirs) possess a major site for the production of granulocytes within a massthat is associated with the meninges (membranes surrounding the central nervous system.) Their heart isfrequently covered with tissue that contains lymphocytes, reticular cells and a small number ofmacrophages. The chondrostean kidney is an important hemopoietic organ; where erythrocytes,granulocytes, lymphocytes and macrophages develop.

Like chondrostean fish, the major immune tissues of bony fish (or teleostei) include the kidney (especiallythe anterior kidney), which houses many different immune cells.[48] In addition, teleost fish possess athymus, spleen and scattered immune areas within mucosal tissues (e.g. in the skin, gills, gut and gonads).Much like the mammalian immune system, teleost erythrocytes, neutrophils and granulocytes are believedto reside in the spleen whereas lymphocytes are the major cell type found in the thymus.[49][50] In 2006, a

A Whale shark, the world's largestfish, is classified as Vulnerable.

lymphatic system similar to that in mammals was described in one species of teleost fish, the zebrafish.Although not confirmed as yet, this system presumably will be where naive (unstimulated) T cellsaccumulate while waiting to encounter an antigen.[51]

B and T lymphocytes bearing immunoglobulins and T cell receptors, respectively, are found in all jawedfishes. Indeed, the adaptive immune system as a whole evolved in an ancestor of all jawed vertebrate.[52]

Conservation

The 2006 IUCN Red List names 1,173 fish species that are threatened with extinction.[53] Included arespecies such as Atlantic cod,[54] Devil's Hole pupfish,[55] coelacanths,[56] and great white sharks.[57]

Because fish live underwater they are more difficult to study than terrestrial animals and plants, andinformation about fish populations is often lacking. However, freshwater fish seem particularly threatenedbecause they often live in relatively small water bodies. For example, the Devil's Hole pupfish occupiesonly a single 3 by 6 metres (10 by 20 ft) pool.[58]

Overfishing

Main article: Overfishing

Overfishing is a major threat to edible fish such as cod andtuna.[59][60] Overfishing eventually causes population (known asstock) collapse because the survivors cannot produce enoughyoung to replace those removed. Such commercial extinctiondoes not mean that the species is extinct, merely that it can nolonger sustain a fishery.

One well-studied example of fishery collapse is the Pacific sardineSadinops sagax caerulues fishery off the California coast. From a 1937 peak of 790,000 long tons(800,000 t) the catch steadily declined to only 24,000 long tons (24,000 t) in 1968, after which the fisherywas no longer economically viable.[61]

The main tension between fisheries science and the fishing industry is that the two groups have differentviews on the resiliency of fisheries to intensive fishing. In places such as Scotland, Newfoundland, andAlaska the fishing industry is a major employer, so governments are predisposed to support it.[62][63] Onthe other hand, scientists and conservationists push for stringent protection, warning that many stockscould be wiped out within fifty years.[64][65]

Habitat destruction

See also: Environmental effects of fishing

A key stress on both freshwater and marine ecosystems is habitat degradation including water pollution,the building of dams, removal of water for use by humans, and the introduction of exotic species.[66] Anexample of a fish that has become endangered because of habitat change is the pallid sturgeon, a NorthAmerican freshwater fish that lives in rivers damaged by human activity.[67]

Exotic species

Avatar of Vishnu as aMatsya

Coat of arms of Narva,Estonia

Introduction of non-native species has occurred in many habitats. One of the best studied examples is theintroduction of Nile perch into Lake Victoria in the 1960s. Nile perch gradually exterminated the lake's500 endemic cichlid species. Some of them survive now in captive breeding programmes, but others areprobably extinct.[68] Carp, snakeheads,[69] tilapia, European perch, brown trout, rainbow trout, and sealampreys are other examples of fish that have caused problems by being introduced into alienenvironments.

Importance to humans

Aquarium collecting

Main article: Fishkeeping#Conservation_and_Science

Economic importance

Main articles: Fish as food, Fishing industry, Aquaculture, and Fishfarming

Recreation

Main articles: Fishkeeping, Recreational fishing, and Angling

Culture

In the Book of Jonah a "great fish" swallowed Jonah the Prophet.Legends of half-human, half-fish mermaids have featured in stories likethose of Hans Christian Andersen and movies like Splash (See Merman,Mermaid).

Among the deities said to take the form of a fish are Ika-Roa of thePolynesians, Dagon of various ancient Semitic peoples, the shark-gods ofHawaiʻi and Matsya of the Hindus. The astrological symbol Pisces isbased on a constellation of the same name, but there is also a second fishconstellation in the night sky, Piscis Austrinus.

Fish have been used figuratively in many different ways, for example theichthys used by early Christians to identify themselves, through to the fishas a symbol of fertility among Bengalis.[70]

Fish feature prominently in art and literature, in movies such as FindingNemo and books such as The Old Man and the Sea. Large fish,particularly sharks, have frequently been the subject of horror movies and thrillers, most notably the novelJaws, which spawned a series of films of the same name that in turn inspired similar films or parodies suchas Shark Tale, Snakehead Terror, and Piranha. However, contrary to popular belief, the red-belliedpiranha is actually a generally timid scavenger species that is unlikely to harm humans.

In the semiotic of Ashtamangala (buddhist symbolism) the golden fish (Sanskrit: Matsya), represents thestate of fearless suspension in samsara, perceived as the harmless ocean, referred to as 'buddha-eyes' or'rigpa-sight'. The fish symbolizes the auspiciousness of all living beings in a state of fearlessness withoutdanger of drowning in the Samsaric Ocean of Suffering, and migrating from teaching to teaching freely

Saint Benno of Meissendepicted with a fish in hand(Church of Saint Benno inMunich)

Fish riders in a 1920s poster of theRepublic of China.

These goldband fusiliers areschooling because their swimming issynchronised

and spontaneously just as fish swim.

They have religious significance in Hindu, Jain and Buddhist traditions but also in Christianity who is firstsignified by the sign of the fish, and especially referring to feeding the multitude in the desert. In thedhamma of Buddha the fish symbolize happiness as they have complete freedom of movement in thewater. They represent fertility and abundance. Often drawn in the form of carp which are regarded in theOrient as sacred on account of their elegant beauty, size and life-span.[3]

The name of the Canadian cityof Coquitlam, British Columbiais derived from Kwikwetlem,which is said to be derived froma Coast Salish term meaning"little red fish".[71]

Terminology

Shoal or school

Main article: Shoaling and schooling

A random assemblage of fish merely using some localisedresource such as food or nesting sites is known simply as anaggregation. When fish come together in an interactive, socialgrouping, then they may be forming either a shoal or a schooldepending on the degree of organisation. A shoal is a looselyorganised group where each fish swims and forages independentlybut is attracted to other members of the group and adjusts itsbehaviour, such as swimming speed, so that it remains close to theother members of the group. Schools of fish are much more tightlyorganised, synchronising their swimming so that all fish move atthe same speed and in the same direction. Shoaling and schoolingbehaviour is believed to provide a variety of advantages.[72]

Examples:

Cichlids congregating at lekking sites form an aggregation.Many minnows and characins form shoals.Anchovies, herrings and silversides are classic examples of schooling fish.

While school and shoal have different meanings within biology, they are often treated as synonyms bynon-specialists, with speakers of British English using "shoal" to describe any grouping of fish, whilespeakers of American English often using "school" just as loosely.

Fish or fishes

Though often used interchangeably, these words have different meanings. Fish is used either as singularnoun or to describe a group of specimens from a single species. Fishes describes a group of differentspecies.[13]

See alsoFor a topical guide to sharks, see Outline of sharks

Angling (sport fishing)AquacultureAquariumCatch and releaseDeep sea fishFish Acute Toxicity SyndromesFish anatomyFish as foodFish developmentFishing (fishing for food)FishkeepingForage fishIchthyologyList of fish common namesList of fish familiesMarine biologyMarine vertebratesOtolith (Bone used for determining the age of a fish)SeafoodWalking fish

Notes1. ^ Goldman, K.J. (1997). "Regulation of body temperature in the white shark, Carcharodon carcharias"

(http://www.mendeley.com/research/temperature-and-activities-of-a-white-shark-carcharodon-carcharias/).Journal of Comparative Physiology. B Biochemical Systemic and Environmental Physiology 167 (6): 423–429.doi:10.1007/s003600050092 (http://dx.doi.org/10.1007%2Fs003600050092). Retrieved 12 October 2011.

2. ^ Carey, F.G.; Lawson, K.D. (1.). "Temperature regulation in free-swimming bluefin tuna". ComparativeBiochemistry and Physiology Part A: Physiology 44 (2): 375–392. doi:10.1016/0300-9629(73)90490-8(http://dx.doi.org/10.1016%2F0300-9629%2873%2990490-8).

3. ^ "FishBase" (http://www.fishbase.org/search.php). FishBase. February 2011 Update. Retrieved 24 May 2011.4. ^ "Monster fish crushed opposition with strongest bite ever" (http://www.smh.com.au/news/science/jaws-of-

steel-on-this-fish-tank/2006/11/29/1164777657728.html). Smh.com.au. November 30, 2006. RetrievedFebruary 26, 2013.

February 26, 2013.5. ^ G. Lecointre & H. Le Guyader, 2007, The Tree of Life: A Phylogenetic Classification, Harvard University

Press Reference Library6. ^ Romer, A.S. & T.S. Parsons. 1977. The Vertebrate Body. 5th ed. Saunders, Philadelphia. (6th ed. 1985)7. ^ Benton, M. J. (1998) The quality of the fossil record of vertebrates. Pp. 269–303, in Donovan, S. K. and

Paul, C. R. C. (eds), The adequacy of the fossil record, Fig. 2. Wiley, New York, 312 pp.8. ^ Shigehiro Kuraku, Daisuke Hoshiyama, Kazutaka Katoh, Hiroshi Suga, Takashi Miyata (1999) Monophyly of

Lampreys and Hagfishes Supported by Nuclear DNA–Coded Genes J Mol Evol (1999) 49:729–7359. ^ J. Mallatt, J. Sullivan (1998) 28S and 18S rDNA sequences support the monophyly of lampreys and hagfishes

Molecular Biology and Evolution V 15, Issue 12, pp 1706–171810. ^ Nelson 2006, pp. 4–511. ^ Nelson 2006, p. 312. ^ Nelson 2006, p. 213. ^ a b c d Helfman, Collette & Facey 1997, p. 314. ^ Tree of life web project – Chordates (http://tolweb.org/Chordata/2499).15. ^ Jr.Cleveland P; Hickman, Larry S. Roberts, Allan L. Larson (2001). Integrated Principles of Zoology.

McGraw-Hill Publishing Co. ISBN 0-07-290961-7.16. ^ Helfman, Collette & Facey 1997, pp. 53–5717. ^ Helfman, Collette & Facey 1997, pp. 33–3618. ^ Froese, Rainer and Pauly, Daniel, eds. (2006). "Periophthalmus barbarus"

(http://www.fishbase.org/Summary/SpeciesSummary.php?id=12803) in FishBase. November 2006 version.19. ^ Froese, Rainer and Pauly, Daniel, eds. (2006). "Phreatobius cisternarum"

(http://www.fishbase.org/summary/SpeciesSummary.php?genusname=Phreatobius&speciesname=cisternarum)in FishBase. November 2006 version.

20. ^ Planet Catfish. "Cat-eLog: Heptapteridae: Phreatobius: Phreatobius sp. (1)"(http://www.planetcatfish.com/catelog/species.php?species_id=646). Planet Catfish. Retrieved 26 November2006.

21. ^ Estudo das Espécies Ícticas do Parque Estadual do Cantão (http://central2.to.gov.br/arquivo/24/199), fishspecies survey of Cantão (in Portuguese)

22. ^ a b "Modifications of the Digestive Tract for Holding Air in Loricariid and Scoloplacid Catfishes"(http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Air.pdf) (PDF). Copeia (3): 663–675. 1998. Retrieved 25 June 2009.

23. ^ Setaro, John F. (1999). Circulatory System. Microsoft Encarta 99.24. ^ a b c d e f g h i j k Helfman, Collette & Facey 1997, pp. 48–4925. ^ Helfman, Collette & Facey 1997, p. 19126. ^ Orr, James (1999). Fish. Microsoft Encarta 99. ISBN 0-8114-2346-8.27. ^ Albert, J.S., and W.G.R. Crampton. 2005. Electroreception and electrogenesis. pp. 431–472 in The

Physiology of Fishes, 3rd Edition. D.H. Evans and J.B. Claiborne (eds.). CRC Press.28. ^ Journal of Undergraduate Life Sciences. "Appropriate maze methodology to study learning in fish"

(http://juls.sa.utoronto.ca/Issues/JULS-Vol2Iss1/JULS-Vol2Iss1-Review3.pdf) (PDF). Retrieved 28 May 2009.29. ^ N. A. Campbell and J. B. Reece (2005). Biology (Seventh ed.). San Francisco, California: Benjamin

Cummings.30. ^ Dunayer, Joan, "Fish: Sensitivity Beyond the Captor's Grasp," The Animals' Agenda, July/August 1991, pp.

12–1831. ^ Vantressa Brown, “Fish Feel Pain, British Researchers Say,” Agence France-Presse, 1 May 2003

(http://www.buzzle.com/editorials/4-30-2003-39769.asp)32. ^ Kirby, Alex (30 April 2003). "Fish do feel pain, scientists say"

(http://news.bbc.co.uk/1/hi/sci/tech/2983045.stm). BBC News. Retrieved 4 January 2010.33. ^ a b c Grandin, Temple; Johnson, Catherine (2005). Animals in Translation. New York, New York: Scribner.

pp. 183–184. ISBN 0-7432-4769-8.34. ^ "Rose, J.D. 2003. A Critique of the paper: "Do fish have nociceptors: Evidence for the evolution of a

vertebrate sensory system"" (http://www.nal.usda.gov/awic/pubs/Fishwelfare/RoseC.pdf) (PDF). Retrieved 21May 2011.

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36. ^ Leake, J. “Anglers to Face RSPCA Check,” The Sunday Times – Britain, 14 March 2004(http://www.timesonline.co.uk/newspaper/0,,176-1037515,00.html)

(http://www.timesonline.co.uk/newspaper/0,,176-1037515,00.html)37. ^ Block BA and Finnerty JR (1993) "Endothermy in fishes: a phylogenetic analysis of constraints,

predispositions, and selection pressures" (http://www.science.siu.edu/zoology/sears/BlockFinnerty1994.pdf)Environmental Biology of Fishes, 40 (3): 283–302. doi:10.1007/BF00002518(http://dx.doi.org/10.1007%2FBF00002518)

38. ^ a b c d e Guimaraes-Cruz, Rodrigo J., Rodrigo J.; Santos, José E. dos; Santos, Gilmar B. (July/Sept. 2005)."Gonadal structure and gametogenesis of Loricaria lentiginosa Isbrücker (Pisces, Teleostei, Siluriformes)".Rev. Bras. Zool. 22 (3): 556–564. doi:10.1590/S0101-81752005000300005(http://dx.doi.org/10.1590%2FS0101-81752005000300005). ISSN 0101-8175 (//www.worldcat.org/issn/0101-8175).

39. ^ Brito, M.F.G.; Bazzoli, N. (2003). "Reproduction of the surubim catfish (Pisces, Pimelodidae) in the SãoFrancisco River, Pirapora Region, Minas Gerais, Brazil" (http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-09352003000500018). Arquivo Brasileiro de Medicina Veterinária e Zootecnia55 (5): 624–633. doi:10.1590/S0102-09352003000500018 (http://dx.doi.org/10.1590%2FS0102-09352003000500018). ISSN 0102-0935 (//www.worldcat.org/issn/0102-0935).

40. ^ Peter Scott: Livebearing Fishes, p. 13. Tetra Press 1997. ISBN 1-56465-193-241. ^ a b Meisner, A & Burns, J: Viviparity in the Halfbeak Genera Dermogenys and Nomorhamphus (Teleostei:

Hemiramphidae). Journal of Morphology 234, pp. 295–317, 199742. ^ Helfman, Collette & Facey 1997, pp. 95–9643. ^ R. C. Cipriano (2001), Furunculosis And Other Diseases Caused By Aeromonas salmonicida. Fish Disease

Leaflet 66. U.S. Department of the Interior.[1] (http://www.lsc.usgs.gov/FHB/leaflets/FHB66.pdf)44. ^ K H Hartman et al. (2004), Koi Herpes Virus (KHV) Disease. Fact Sheet VM-149. University of Florida

Institute of Food and Agricultural Sciences.[2] (http://edis.ifas.ufl.edu/pdffiles/VM/VM11300.pdf)45. ^ Helfman, Collette & Facey 1997, p. 38046. ^ Richard L. Wyman and Jack A. Ward (1972). A Cleaning Symbiosis between the Cichlid Fishes Etroplus

maculatus and Etroplus suratensis. I. Description and Possible Evolution. Copeia, Vol. 1972, No. 4, pp. 834–838.

47. ^ A.G. Zapata, A. Chiba and A. Vara. Cells and tissues of the immune system of fish. In: The Fish ImmuneSystem: Organism, Pathogen and Environment. Fish Immunology Series. (eds. G. Iwama and T.Nakanishi,),New York, Academic Press, 1996, pp. 1–55.

48. ^ D.P. Anderson. Fish Immunology. (S.F. Snieszko and H.R. Axelrod, eds), Hong Kong: TFH Publications,Inc. Ltd., 1977.

49. ^ S. Chilmonczyk (1992). The thymus in fish: development and possible function in the immune response 2.Annual Review of Fish Diseases. pp. 181–200.

50. ^ J.D. Hansen and A.G. Zapata (1998). Lymphocyte development in fish and amphibians 166. ImmunologicalReviews. pp. 199–220.

51. ^ Kucher et al., (2006). Development of the zebrafish lymphatic system requires VegFc signalling 16. CurrentBiology. pp. 1244–1248.

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53. ^ "Table 1: Numbers of threatened species by major groups of organisms (1996–2004)"(http://web.archive.org/web/20060630054235/http://www.iucnredlist.org/info/tables/table1). iucnredlist.org.Archived from the original (http://www.iucnredlist.org/info/tables/table1) on 30 June 2006. Retrieved 18January 2006.

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BBC News. 5 January 2007. Retrieved January 18, 2006.60. ^ "Tuna groups tackle overfishing" (http://news.bbc.co.uk/1/hi/world/asia-pacific/6301187.stm). BBC News. 26

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2006. Retrieved 18 January 2006.63. ^ "EU fish quota deal hammered out" (http://news.bbc.co.uk/1/hi/world/europe/6197433.stm). BBC News. 21

December 2006. Retrieved 18 January 2006.64. ^ "Ocean study predicts the collapse of all seafood fisheries by 2050"

(http://www.physorg.com/news81778444.html). Retrieved 13 January 2006.65. ^ "Atlantic bluefin tuna could soon be commercially extinct"

(http://web.archive.org/web/20070430205610/http://www.panda.org/about_wwf/where_we_work/europe/what_we_do/mediterranean/about/marine/bluefin_tuna/tuna_at_risk/index.cfm). Archived from the original(http://www.panda.org/about_wwf/where_we_work/europe/what_we_do/mediterranean/about/marine/bluefin_tuna/tuna_at_risk/index.cfm) on 30 April 2007. Retrieved January 18, 2006.

66. ^ Helfman, Collette & Facey 1997, p. 46367. ^ "Threatened and Endangered Species: Pallid Sturgeon Scaphirhynchus Fact Sheet"

(http://www.mt.nrcs.usda.gov/news/factsheets/pallidsturgeon.html). Retrieved 18 January 2006.68. ^ Spinney, Laura (4 August 2005). "The little fish fight back"

(http://www.guardian.co.uk/life/feature/story/0,,1541613,00.html). The Guardian (London). Retrieved 18January 2006.

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86542-256-7.

ReferencesHelfman, G.; Collette, B.; Facey, D. (1997). The Diversity of Fishes. Blackwell Publishing. ISBN 0-86542-256-7.Eschmeyer, William N; Fong, Jon David (2013). "Catalog of Fishes"(http://researcharchive.calacademy.org/research/ichthyology/). California Academy of Sciences.Helfman, G; Collette, BB; Facey, DH; Bowen, BW (2009). The Diversity of Fishes: Biology, Evolution, andEcology (http://www.blackwellpublishing.com/helfman/) (2nd ed.). Wiley-Blackwell. ISBN 978-1-4051-2494-2.Moyle, PB; Cech, JJ (2003). Fishes, An Introduction to Ichthyology (5th ed.). Benjamin Cummings.ISBN ISBN 978-0-13-100847-2.Nelson, Joseph S. (2006). Fishes of the World(http://web.archive.org/web/20130305052159/http://www.somas.stonybrook.edu/~conover/Textbooks/Fishes%20of%20the%20World,%204th%20ed.%20Joseph%20S.%20Nelson.pdf) (PDF) (4th ed.). John Wiley & Sons.ISBN 9780471756446. Archived from the original(http://www.somas.stonybrook.edu/~conover/Textbooks/Fishes%2520of%2520the%2520World%2C%25204th%2520ed.%2520Joseph%2520S.%2520Nelson.pdf) on March 5, 2013. Retrieved April 30, 2013.

Further readingMoyle, Peter B (1993) Fish: An Enthusiast's Guide (http://books.google.co.nz/books?id=cu-J9tqy4IQC&printsec=frontcover&dq=Fish:+An+Enthusiast%27s+Guide&hl=en&sa=X&ei=YUp3Up_UCo6jiAf3z4CADA&ved=0CC8Q6AEwAA#v=onepage&q=Fish%3A%20An%20Enthusiast%27s%20Guide&f=false) University of California Press. ISBN 9780520916654 – good lay text.Shubin, Neil (2009) Your inner fish: A journey into the 3.5 billion year history of the human body(http://books.google.co.nz/books?id=c008kdNwR1cC&dq=%22Your+Inner+Fish%22&hl=en&sa=X&ei=1qOyUJCqOorsmAX5xYCwDg&ved=0CDAQ6AEwAA) Vintage Books. ISBN 9780307277459. UCTV interview

(http://www.uctv.tv/search-details.aspx?showID=16412)

External linksANGFA (http://db.angfa.org.au/) – Illustrated database of freshwater fishes of Australia and NewGuineaFischinfos.de (http://www.fischinfos.de/) – Illustrated database of the freshwater fishes of Germany(German)FishBase online (http://www.fishbase.org/) – Comprehensive database with information on over29,000 fish speciesFisheries and Illinois Aquaculture Center (http://fishdata.siu.edu/) – Data outlet for fisheries andaquaculture research center in the central USPhilippines Fishes (http://www.poppe-images.com/) – Database with thousands of Philippine Fishesphotographed in natural habitatThe Native Fish Conservancy (http://www.nativefish.org/) – Conservation and study of NorthAmerican freshwater fishesUnited Nation (http://www.fao.org/fi/website/FIRetrieveAction.do?dom=topic&fid=2888) –Fisheries and Aquaculture Department: Fish and seafood utilizationUniversity of Washington Libraries Digital Collections (http://content.lib.washington.edu/cgi-bin/queryresults.exe?CISOOP=adv&CISORESTMP=%2Fsite-templates%2Fsearch_results-sub.html&CISOVIEWTMP=%2Fsite-templates%2Fitem_viewer.html&CISOMODE=thumb&CISOGRID=thumbnail%2CA%2C1%3Btitle%2CA%2C1%3Bsubjec%2CA%2C0%3Bdescri%2C200%2C0%3B0%2CA%2C0%3B10&CISOBIB=title%2CA%2C1%2CN%3Bsubjec%2CA%2C0%2CN%3Bdescri%2CK%2C0%2CN%3B0%2CA%2C0%2CN%3B0%2CA%2C0%2CN%3B10&CISOTHUMB=3%2C5&CISOTITLE=10&CISOPARM=%2Ffishimages%3Asubjec%3Afish&x=20&y=1) – Digital collection offreshwater and marine fish images

Charles B. Davenport; Ernest Ingersoll (1905). "Fish". New International Encyclopedia.

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