An electric fish is a fish that can generate electric fields. It is said to be electrogenic; a fish that has the ability to detect electric fields is said to be electroreceptive. Most fish that are electrogenic are also electroreceptive. Electric fish species can be found both in the sea and in freshwater rivers of South America and Africa. Many fishes such as sharks, rays and catfishes can detect electric fields, and are thus electroreceptive, but as they cannot generate an electric field they are not classified as electric fish. Most common bony fish (teleosts), including most fish that kept in aquaria or caught for food, are neither electrogenic nor electroreceptive.

Strongly and weakly electric fish

Electric fish produce their electric fields from a specialized structure called an electric organ. This is made up of modified muscle or nerve cells, which became specialized for producing electric fields. Typically this organ is located in the tail of the electric fish. The electrcial output of the organ is called the electric organ discharge (EOD).

Fish that have an EOD that is powerful enough to stun their prey are called strongly electric fish. The amplitude of the signal can range from 10 to 500 volts with a current of up to 1 ampere. Typical examples are the electric eel (Electrophorus electricus; not a true eel but a knifefish), the electric catfishes (family Malapteruridae), and electric rays (order Torpediniformes).

By contrast, weakly electric fish generate a discharge that is typically less than one volt in amplitude. These are too weak to stun prey, but are used for navigation, object detection (electrolocation) and communication with other electric fish (electrocommunication). Some of the best known and most studied examples are Peters' elephantnose fish (Gnathonemus petersi) and the black ghost knifefish (Apteronotus albifrons).

The EOD waveform takes two general forms depending on the species. In some species the waveform is continuous and almost sinusoidal (for example the genera Apteronotus, Eigenmannia and Gymnarchus) and these are said to have a wave-type EOD. In other species, the EOD waveform consists of brief pulses separated by longer gaps (for example Gnathonemus, Gymnotus, Raja) and these are said to have a pulse-type EOD.

Table of electric fish

This is a table of all known electric fish species within fresh water. In salt water there is only one order, the Torpediniformes (electric rays), inside the chondrichthyes that shows species generating even strong electric pulses (genus Torpedo spp., which counts 22 known species).

Taxon	Species (348)
Gymnotiformes
Apteronotidae (46 species in 13 genera)	Adontosternarchus balaenops, Adontosternarchus clarkae, Adontosternarchus devenanzii, Adontosternarchus sachsi, Apteronotus albifrons, Apteronotus apurensis, Apteronotus bonapspeciesii, Apteronotus brasiliensis, Apteronotus caudimaculosus, Apteronotus cuchillejo, Apteronotus cuchillo, Apteronotus ellisi, Apteronotus eschmeyeri, Apteronotus jurubidae, Apteronotus leptorhynchus, Apteronotus macrolepis, Apteronotus macrostomus, Apteronotus magdalenensis, Apteronotus marauna, Apteronotus mariae, Apteronotus rostratus, Apteronotus spurrellii, Compsaraia compsa, Magosternarchus duccis, Magosternarchus raptor, Megadontognathus cuyuniense, Megadontognathus kaitukaensis, Orthosternarchus tamandua, Parapteronotus hasemani, Platyurosternarchus macrostomus, Porotergus gimbeli, Porotergus gymnotus, Sternarchella curvioperculata, Sternarchella orthos, Sternarchella schotti, Sternarchella sima, Sternarchella terminalis, Sternarchogiton nattereri, Sternarchogiton porcinum, Sternarchorhamphus muelleri, Sternarchorhynchus britskii, Sternarchorhynchus curvirostris, Sternarchorhynchus mesensis, Sternarchorhynchus mormyrus, Sternarchorhynchus oxyrhynchus, Sternarchorhynchus roseni
Gymnotidae (29 species in 1 genus)	Gymnotus anguillaris, Gymnotus arapaima, Gymnotus ardilai, Gymnotus bahianus, Gymnotus carapo, Gymnotus cataniapo, Gymnotus choco, Gymnotus coatesi, Gymnotus coropinae, Gymnotus cylindricus, Gymnotus diamantinensis, Gymnotus esmeraldas, Gymnotus henni, Gymnotus inaequilabiatus, Gymnotus javari, Gymnotus jonasi, Gymnotus maculosus, Gymnotus mamiraua, Gymnotus melanopleura, Gymnotus onca, Gymnotus panamensis, Gymnotus pantanal, Gymnotus pantherinus, Gymnotus paraguensis, Gymnotus pedanopterus, Gymnotus stenoleucus, Gymnotus sylvius, Gymnotus tigre, Gymnotus ucamara
Electrophoridae (1 species in 1 genus)	Electrophorus electricus
Hypopomidae (14 species in 7 genera)	Brachyhypopomus beebei, Brachyhypopomus brevirostris, Brachyhypopomus diazi, Brachyhypopomus janeiroensis, Brachyhypopomus occidentalis, Brachyhypopomus pinnicaudatus, Hypopomus speciesedi, Hypopygus lepturus, Hypopygus neblinae, Microsternarchus bilineatus, Racenisia fimbriipinna, Steatogenys duidae, Steatogenys elegans, Stegostenopos cryptogenes
Rhamphichthyidae (15 species in 3 genera)	Gymnorhamphichthys hypostomus, Gymnorhamphichthys petiti, Gymnorhamphichthys rondoni, Gymnorhamphichthys rosamariae, Iracema caiana, Rhamphichthys apurensis, Rhamphichthys atlanticus, Rhamphichthys drepanium, Rhamphichthys hahni, Rhamphichthys lineatus, Rhamphichthys longior, Rhamphichthys marmoratus, Rhamphichthys pantherinus, Rhamphichthys rostratus, Rhamphichthys schomburgki
Sternopygidae (28 species in 5 genera)	Archolaemus blax, Distocyclus conirostris, Distocyclus goajira, Eigenmannia humboldtii, Eigenmannia limbata, Eigenmannia macrops, Eigenmannia microstoma, Eigenmannia nigra, Eigenmannia trilineata, Eigenmannia vicentespelaea, Eigenmannia virescens, Rhabdolichops caviceps, Rhabdolichops eastwardi, Rhabdolichops electrogrammus, Rhabdolichops jegui, Rhabdolichops stewspeciesi, Rhabdolichops troscheli, Rhabdolichops zareti, Sternopygus aequilabiatus, Sternopygus arenatus, Sternopygus astrabes, Sternopygus branco, Sternopygus castroi, Sternopygus dariensis, Sternopygus macrurus, Sternopygus obtusirostris, Sternopygus pejeraton, Sternopygus xingu
Osteoglossiformes
Gymnarchidae (1 species in 1 genus)	Gymnarchus niloticus
Mormyridae (203 species in 18 genera)	Boulengeromyrus knoepffleri, Brienomyrus adustus, Brienomyrus brachyistius, Brienomyrus curvifrons, Brienomyrus hopkinsi, Brienomyrus kingsleyae eburneensis, Brienomyrus kingsleyae kingsleyae, Brienomyrus longianalis, Brienomyrus longicaudatus, Brienomyrus niger, Brienomyrus sphekodes, Brienomyrus tavernei, Campylomormyrus alces, Campylomormyrus bredoi, Campylomormyrus cassaicus, Campylomormyrus christyi, Campylomormyrus curvirostris, Campylomormyrus elephas, Campylomormyrus luapulaensis, Campylomormyrus mirus, Campylomormyrus numenius, Campylomormyrus orycteropus, Campylomormyrus phantasticus, Campylomormyrus rhynchophorus, Campylomormyrus tamandua, Campylomormyrus tshokwe, Genyomyrus donnyi, Gnathonemus barbatus, Gnathonemus echidnorhynchus, Gnathonemus longibarbis, Gnathonemus petersii, Heteromormyrus pauciradiatus, Hippopotamyrus aelsbroecki, Hippopotamyrus ansorgii, Hippopotamyrus batesii, Hippopotamyrus castor, Hippopotamyrus discorhynchus, Hippopotamyrus grahami, Hippopotamyrus harringtoni, Hippopotamyrus macrops, Hippopotamyrus macroterops, Hippopotamyrus pappenheimi, Hippopotamyrus paugyi, Hippopotamyrus pictus, Hippopotamyrus psittacus, Hippopotamyrus retrodorsalis, Hippopotamyrus smithersi, Hippopotamyrus szaboi, Hippopotamyrus weeksii, Hippopotamyrus wilverthi, Hyperopisus bebe bebe, Hyperopisus bebe occidentalis, Isichthys henryi, Ivindomyrus opdenboschi, Marcusenius rhodesianus, Marcusenius sanagaensis, Marcusenius schilthuisiae, Marcusenius senegalensis gracilis, Marcusenius senegalensis pfaffi, Marcusenius senegalensis senegalensis, Marcusenius stanleyanus, Marcusenius thomasi, Marcusenius ussheri, Marcusenius victoriae, Marcusenius abadii, Marcusenius annamariae, Marcusenius bentleyi, Marcusenius brucii, Marcusenius cuangoanus, Marcusenius cyprinoides, Marcusenius deboensis, Marcusenius dundoensis, Marcusenius friteli, Marcusenius furcidens, Marcusenius fuscus, Marcusenius ghesquierei, Marcusenius greshoffii, Marcusenius intermedius, Marcusenius kutuensis, Marcusenius leopoldianus, Marcusenius livingstonii, Marcusenius macrolepidotus angolensis, Marcusenius macrolepidotus macrolepidotus, Marcusenius macrophthalmus, Marcusenius mento, Marcusenius meronai, Marcusenius monteiri, Marcusenius moorii, Marcusenius ntemensis, Marcusenius nyasensis, Marcusenius rheni, Mormyrops anguilloides, Mormyrops attenuatus, Mormyrops batesianus, Mormyrops breviceps, Mormyrops caballus, Mormyrops citernii, Mormyrops curtus, Mormyrops curviceps, Mormyrops engystoma, Mormyrops furcidens, Mormyrops intermedius, Mormyrops lineolatus, Mormyrops mariae, Mormyrops masuianus, Mormyrops microstoma, Mormyrops nigricans, Mormyrops oudoti, Mormyrops parvus, Mormyrops sirenoides, Mormyrus bernhardi, Mormyrus caballus asinus, Mormyrus caballus bumbanus, Mormyrus caballus caballus, Mormyrus caballus lualabae, Mormyrus casalis, Mormyrus caschive, Mormyrus cyaneus, Mormyrus felixi, Mormyrus goheeni, Mormyrus hasselquistii, Mormyrus iriodes, Mormyrus kannume, Mormyrus lacerda, Mormyrus longirostris, Mormyrus macrocephalus, Mormyrus macrophthalmus, Mormyrus niloticus, Mormyrus ovis, Mormyrus rume proboscirostris, Mormyrus rume rume, Mormyrus subundulatus, Mormyrus tapirus, Mormyrus tenuirostris, Mormyrus thomasi, Myomyrus macrodon, Myomyrus macrops, Myomyrus pharao, Oxymormyrus boulengeri, Oxymormyrus zanclirostris, Paramormyrops gabonensis, Paramormyrops jacksoni, Petrocephalus ansorgii, Petrocephalus balayi, Petrocephalus bane bane, Petrocephalus bane comoensis, Petrocephalus binotatus, Petrocephalus bovei bovei, Petrocephalus bovei guineensis, Petrocephalus catostoma catostoma, Petrocephalus catostoma congicus, Petrocephalus catostoma haullevillei, Petrocephalus catostoma tanensis, Petrocephalus christyi, Petrocephalus cunganus, Petrocephalus gliroides, Petrocephalus grandoculis, Petrocephalus guttatus, Petrocephalus hutereaui, Petrocephalus keatingii, Petrocephalus levequei, Petrocephalus microphthalmus, Petrocephalus pallidomaculatus, Petrocephalus pellegrini, Petrocephalus sauvagii, Petrocephalus schoutedeni, Petrocephalus simus, Petrocephalus soudanensis, Petrocephalus squalostoma, Petrocephalus sullivani, Petrocephalus tenuicauda, Petrocephalus wesselsi, Pollimyrus adspersus, Pollimyrus brevis, Pollimyrus castelnaui, Pollimyrus isidori fasciaticeps, Pollimyrus isidori isidori, Pollimyrus isidori osborni, Pollimyrus maculipinnis, Pollimyrus marchei, Pollimyrus nigricans, Pollimyrus nigripinnis, Pollimyrus pedunculatus, Pollimyrus petherici, Pollimyrus petricolus, Pollimyrus plagiostoma, Pollimyrus pulverulentus, Pollimyrus schreyeni, Pollimyrus stappersii kapangae, Pollimyrus stappersii stappersii, Pollimyrus tumifrons, Stomatorhinus ater, Stomatorhinus corneti, Stomatorhinus fuliginosus, Stomatorhinus humilior, Stomatorhinus kununguensis, Stomatorhinus microps, Stomatorhinus patrizii, Stomatorhinus polli, Stomatorhinus polylepis, Stomatorhinus puncticulatus, Stomatorhinus schoutedeni, Stomatorhinus walkeri
Siluriformes
Malapteruridae (11 species in 1 genus)	Malapterurus beninensis, Malapterurus cavalliensis, Malapterurus electricus, Malapterurus leonensis, Malapterurus microstoma, Malapterurus minjiriya, Malapterurus monsembeensis, Malapterurus oguensis, Malapterurus shirensis, Malapterurus tanganyikaensis, Malapterurus tanoensis

References

• Bullock TH, Heiligenberg W (eds) (1986) Electroreception. Wiley, 722 pp.
• Heiligenberg W (1991) Neural nets in electric fish. MIT Press, 179 pp.
• Moller P (1995) Electric Fishes: History and Behavior. Chapman & Hall, 583 pp.

Links

• Electric Fish, Mark E. Nelson, Beckman Institute Neuroscience Program, University of Illinois at Urbana-Champaign, Accessed 11/2006, [1]

This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.

Origins

Stone Age fishing hook made from bone.

"Fishing" is a very ancient practice that dates back at least to the Mesolithic period which began about 10,000 years ago. Archaeological features such as shell middens, discarded fish bones and cave paintings show that sea foods were important for survival and consumed in significant quantities. During this period, most people lived a hunter-gather lifestyle and were, of necessity, constantly on the move. However, where there are early examples of permanent settlements (though not necessarily permanently occupied) such as those at Lepenski Vir, they are almost always associated with fishing as a major source of food.

The Neolithic culture and technology spread worldwide between 4,000 and 8,000 years ago. With the new technologies of farming and pottery came basic forms of all the main fishing methods that are still used today.

Fishing may even pre-date the development of modern humans. The aquatic ape hypothesis, a controversial proposal, suggests that the ancestors of modern humans went through one or more periods of time living in a semi-aquatic setting and gathered most of their food from shallow coastal or other waters before their descendants returned to a more land-based existence.

Ancient representations

Egyptians bringing in fish, and splitting for salting.

The ancient river Nile was full of fish; fresh and dried fish were a staple food for much of the population. The Egyptians invented various implements and methods for fishing and these are clearly illustrated in tomb scenes, drawings, and papyrus documents. Simple reed boats served for fishing. Woven nets, weir baskets made from willow branches, harpoons and hook and line (the hooks having a length of between eight millimetres and eighteen centimetres) were all being used. By the 12th dynasty, metal hooks with barbs were being used. As is fairly common today, the fish were clubbed to death after capture. Nile perch, catfish and eels were among the most important fish. Some representations hint at fishing being pursued as a pastime.

Poseidon/Neptune sculpture in Copenhagen Port.

Fishing scenes are rarely represented in ancient Greek culture, a reflection of the low social status of fishing. There is a wine cup, dating from 510–500 BC, that shows a boy crouched on a rock with a fishing-rod in his right hand and a basket in his left. In the water below, a rounded object of the same material with an opening on the top. This has been identified as a fish-cage used for keeping live fish, or as a fish-trap. It is clearly not a net. This object is currently in the Museum of Fine Arts, Boston.

Pictorial evidence of Roman fishing comes from mosaics which show fishing from boats with rod and line as well as nets. Various species such as conger, lobster, sea urchin, octopus and cuttlefish are illustrated. In a parody of fishing, a type of gladiator called retiarius was armed with a trident and a casting-net. He would fight against the murmillo, who carried a short sword and a helmet with the image of a fish on the front.

The Greco-Roman sea god Neptune is depicted as wielding a fishing trident.

Ancient literature

There are numerous references to fishing in ancient literature; in most cases, however, the descriptions of nets and fishing-gear do not go into detail, and the equipment is described in general terms. An early example from the Bible in Job 41:7: Canst thou fill his skin with barbed irons? or his head with fish spears?.

The Greek historian Polybius (ca 203 BC-120 BC), in his Histories, describes hunting for swordfish by using a harpoon with a barbed and detachable head.

Oppian of Corycus, a Greek author wrote a major treatise on sea fishing, the Halieulica or Halieutika, composed between 177 and 180. This is the earliest such work to have survived intact to the modern day. Oppian describes various means of fishing including the use of nets cast from boats, scoop nets held open by a hoop, spears and tridents, and various traps "which work while their masters sleep". Oppian’s description of fishing with a "motionless" net is also very interesting:

The fishers set up very light nets of buoyant flax and wheel in a circle round about while they violently strike the surface of the sea with their oars and make a din with sweeping blow of poles. At the flashing of the swift oars and the noise the fish bound in terror and rush into the bosom of the net which stands at rest, thinking it to be a shelter: foolish fishes which, frightened by a noise, enter the gates of doom. Then the fishers on either side hasten with the ropes to draw the net ashore.

From ancient representations and literature it is clear that fishing boats were typically small, lacking a mast or sail, and were only used close to the shore.

In traditional Chinese history, history begins with three semi-mystical and legendary individuals who taught the Chinese the arts of civilization around 2800–2600 BC: of these Fu Hsi was reputed to be the inventor of writing, hunting, trapping, and fishing.

This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.

Hand fishing

Ama diver in Japan

It is possible to fish with minimal equipment by using only the hands. In the USA catching catfish in this way is known as noodling. In the British Isles, the practice of catching trout by hand is known as trout tickling; it is an art mentioned several times in the plays of Shakespeare.

Trout binning is a method of fishing, possibly fictional, performed with a sledgehammer.

Divers can catch lobsters by hand.

Pearl diving is the practice of hunting for oysters by free-diving to depths of up to 30 m.

Hand-line fishing is a technique requiring a fishing line with a weight and one or more lure-like hooks.

Catching fish by hand is currently illegal in the United States in the state of Kansas.

Spear and bow fishing

Menominees spearfishing salmon at night by torchlight and canoe on Fox River

Spear fishing is an ancient method of fishing and may be conducted with an ordinary spear or a specialised variant such as an eel spear[9][10] or the trident. A small trident type spear with a long handle is used in the American South and Midwest for "gigging" bullfrogs with a bright light at night, or for gigging carp and other fish in the shallows.

Traditional spear fishing is restricted to shallow waters, but the development of the speargun has made the method much more efficient. With practice, divers are able to hold their breath for up to four minutes and sometimes longer; of course, a diver with underwater breathing equipment can dive for much longer periods.

Bow fishers use a bow and arrow to kill fish in shallow water from above.

Fishing nets

Fishing with nets in Cà Mau, Vietnam.

All fishing nets are meshes usually formed by knotting a relatively thin thread. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and are still used in certain areas.

A small hand net held open by a hoop and possibly on the end of a long stiff handle has been known since antiquity and may be used for sweeping up fish near the water surface. Such a net used by an angler to aid in landing a captured fish is known as a landing net. In England, hand netting is the only legal way of catching eels and has been practised for thousands of years on the River Parrett and River Severn.

A casting net is circular with a weighted periphery. Sizes vary up to about 4 m diameter. The net is thrown by hand in such a manner that it spreads out on the water and sinks. Fish are caught as the net is hauled back in.

Coracle-fishing is performed by two men, each seated in his coracle and with one hand holding the net while, with the other, he plies his paddle. When a fish is caught, each hauls up his end of the net until the two coracles are brought to touch and the fish is then secured.

The Chinese fishing nets (Cheena vala) found at Kochi in India are an example of shore operated lift nets. Huge mechanical contrivances hold out horizontal nets of 20 m or more across. The nets are dipped into the water and raised again, but otherwise cannot be moved.

A seine is a large fishing net that may be arranged in a number of different ways. In purse seine fishing the net hangs vertically in the water by attaching weights along the bottom edge and floats along the top. A simple and commonly used fishing technique is beach seining, where the seine net is operated from the shore. Danish seine is a method which has some similarities with trawling.

Trawling is a method of fishing that involves actively pulling a fishing net through the water behind one or more boats.

A gillnet catches fish which try to pass through it by snagging on the gill covers. Thus trapped, the fish can neither advance through the net nor retreat.

Ghost nets are nets that have been lost at sea. They may continue to be a menace to wildlife for many years.

A fisherman in Kerala, India

Dredging

There are types of dredges used for collecting scallops or oysters from the seabed. They tend to have the form of a scoop made of chain mesh and they are towed by a fishing boat. Scallop dredging is very destructive to the seabed, and nowadays is often replaced by mariculture or by scuba diving to collect the scallops.

Fishing lines

Fish are caught with a fishing line by encouraging a fish to bite upon a fish hook or a gorge. A fishing hook will pierce the mouthparts of a fish and may be barbed to make escape less likely. A gorge is buried in the bait such that it would be swallowed end first. The tightening of the line would fix it cross-wise in the quarry's stomach or gullet and so the capture would be assured.

Fishing with a hook and line is called angling. In addition to the use of the hook and line used to catch a fish, a heavy fish may be landed by using a landing net or a hooked pole called a gaff.

Trolling is a technique in which a fishing lure on a line is drawn through the water. Trolling from a moving boat is a technique of big-game fishing and is used when fishing from boats to catch large open-water species such as tuna and marlin. Trolling is also a freshwater angling technique most often used to catch trout. Trolling is also an effective way to catch northern pike in the great lakes. This technique allows anglers to cover a large body of water in a short time.

Long-line fishing is a commercial fishing technique that uses hundreds or even thousands of baited hooks hanging from a single line.

Snagging is a technique where the object is to hook the fish in the body. Generally, a large treble hook with a heavy sinker is cast into a river containing a large amount of fish, such as a Salmon, and is quickly jerked and reeled in. Due to the often illegal nature of this method some practitioners have added methods to disguise the practice, such as adding bait or reducing the jerking motion.

Kite fishing

Kite fishing is presumed to have been first invented in China. It was, and is, also used by the people of New Guinea and other Pacific Islands - either by cultural diffusion from China or independent invention.

Kites can provide the boatless fishermen access to waters that would otherwise be available only to boats. Similarly, for boat owners, kites provide a way to fish in areas where it is not safe to navigate such as shallows or coral reefs where fish may be plentiful. Kites can also be used for trolling a lure through the water.

Suitable kites may be of very simple construction. Those of Tobi Island are a large leaf stiffened by the ribs of the fronds of the coconut palm. The fishing line may be made from coconut fibre and the lure made from spiders webs.

Modern kitefishing is popular in New Zealand, where large delta kites of synthetic materials are used to fish from beaches[1][2], taking a line and hooks far out past the breakers.

Ice fishing

Ice fishing is the practice of catching fish with lines and hooks through an opening in the ice on a frozen body of water. It is practised by hunter-gatherers such as the Inuit and by anglers in other cold or continental climates.

Fish traps

Catching lobster

Traps are culturally almost universal and seem to have been independently invented many times. There are essentially two types of trap, a permanent or semi-permanent structure placed in a river or tidal area and pot-traps that are baited to attract prey and periodically lifted.

Indigenous Australians were, prior to European colonisation, most populous in Australia's better-watered areas such as the Murray-Darling river system of the south-east. Here, where water levels fluctuate seasonally, indigenous people constructed ingenious stone fish traps.[14] Unfortunately, most have been completely or partially destroyed. The largest and best known were the Brewarrina fish traps on the Barwon River at Brewarrina in New South Wales, which fortunately are at least partly preserved.[15] The Brewarinna fish traps caught huge numbers of migratory native fish as the Barwon River rose in flood and then fell. In southern Victoria, indigenous people created an elaborate systems of canals, some more than 2 km long. The purpose of these canals was the encouragement and catching of eels, a fish of short coastal rivers (as opposed to rivers of the Murray-Darling system). The eels were caught by a variety of traps including stone walls constructed across canals with a net placed across an opening in the wall. Traps at different levels in the marsh came into operation as the water level rose and fell. Somewhat similar stone wall traps were constructed by native American Pit River people in north-eastern California.

A technique called dam fishing is used by the Baka pygmies. This involves the construction of a temporary dam resulting in a drop in the water levels downstream — allowing fish to be easily collected.

In medieval Europe, large fishing weir structures were constructed from wood posts and wattle fences. 'V' shaped structures in rivers could be as long as 60 m and worked by directing fish towards fish traps or nets. Such fish traps were evidently controversial in medieval England. The Magna Carta includes a clause requiring that they be removed:

All fish-weirs shall be removed from the Thames, the Medway, and throughout the whole of England, except on the sea coast.

Basket weir fish traps were widely used in ancient times. They are shown in medieval illustrations and surviving examples have been found. Basket weirs are about 2 m long and comprise two wicker cones, one inside the other — easy to get into and hard to get out.

The Wagenya people, in the Democratic Republic of Congo, build a huge system of wooden tripods across the river. These tripods are anchored on the holes naturally carved in the rock by the water current. To these tripods are anchored large baskets, which are lowered in the rapids to "sieve" the waters for fish. It is a very selective fishing, as these baskets are quite big and only large size fish are trapped. Twice a day the adults Wagenya people pull out these baskets to check whether there are any fish caught; in which case somebody will dive into the river to fetch it.

Lobster and crab pots

Pot traps are typically used to catch crustaceans such as crabs, lobsters and crayfish. Pot traps such as the lobster trap may be constructed in various shapes, each is a mesh box designed with a convoluted entrance that makes entry much easier than exit. The pots are baited and lowered into the water and checked daily. Similar traps are used in many areas to capture bait fish.

Trained animals

Chinese man with fishing cormorant

In China and Japan, the practice of cormorant fishing is thought to date back some 1300 years. Fishermen use the natural fish-hunting instincts of the cormorants to catch fish, but a metal ring placed round the bird's neck prevents large, valuable fish being swallowed. The fish are instead collected by the fisherman.

The people of Nauru used trained frigatebirds to fish on reefs.

The practice of tethering a remora, a sucking fish, to a fishing line and using the remora to capture sea turtles probably originated in the Indian Ocean. The earliest surviving records of the practice are Peter Martyr d'Anghera's 1511 accounts of the second voyage of Columbus to the New World (1494). However, these accounts are probably apocryphal, and based on earlier, no longer extant accounts from the Indian Ocean region.

Dating from the 1500s in Portugal, Portuguese Water Dogs were used by fishermen to send messages between boats, to retrieve fish and articles from the water, and to guard the fishing boats. Labrador Retrievers have been used by fishermen to assist in bringing nets to shore; the dog would grab the floating corks on the ends of the nets and pull them to shore.

Toxins

Many hunter gatherer cultures use poisonous plants to stun fish so that they become easy to collect by hand. Some of these poisons paralyse the fish, others are thought to work by removing oxygen from the water.

Cyanides are used to capture live fish near coral reefs for the aquarium and seafood market. This illegal fishing occurs mainly in or near the Philippines, Indonesia, and the Caribbean to supply the 2 million marine aquarium owners in the world. Many fish caught in this fashion die either immediately or in shipping. Those that survive often die from shock or from massive digestive damage. The high concentrations of cyanide on reefs harvested in this fashion damages the coral polyps and has also resulted in cases of cyanide poisoning among local fishermen and their families.

Explosives

Dynamite or blast fishing, is done easily and cheaply with dynamite or homemade bombs made from locally available materials. Fish are killed by the shock from the blast and are then skimmed from the surface or collected from the bottom. The explosions indiscriminately kill large numbers of fish and other marine organisms in the vicinity and can damage or destroy the physical environment. Explosions are particularly harmful to coral reefs. Blast fishing is also illegal in many waterways around the world.

Electrofishing

Scientists carrying out a population and species survey using electrofishing equipment

A relatively new fishing technique is electrofishing, typically used for stream classification surveys and catching brood stock for hatcheries, or making estimates of populations in a body of water. A gated pulse of direct current is used to cause muscular contractions in a fish, called galvanotaxis, causing them to turn towards the source of the electrical current and swim towards it when correct pulse speeds and durations are used, along with correct current.

A low voltage or short pulse with long gaps will cause the fish to swim away from the device, and high voltage or long pulses with short rests can cause galvanonarcosis, or unconsciousness. Techniques for setting pulse length and patterns, current and voltage require great skill to fish effectively without killing or injuring fish if they are to be left unharmed. Dissolved minerals in the water can decrease resistance causing less of the current to pass through the fish, whereas fish recently entering fresh water from the ocean have high salinity and are more prone to electric shock. Also the smaller the fish, and consequently the less surface area in contact with the water, the higher the current required to produce galvanotaxis. Smaller fish also require shorter pulses, closer together, while large fish should have longer pulses at lower power and longer gaps between pulses.

Rigs can be battery powered back-packs or powered by a generator if they are mounted in a boat. They are typically equipped with a "dead-man switch" and a tilt switch to disable the device if the unit is tipped or the operator incapacitated. Protective equipment must be worn to isolate the operator and prevent electrocution.

Electro-fishing is also used to illegally catch Razorfish or Spoots, using a boat based generator. Current is passed into the sediment causing the Razorfish to 'jump' and be harvested by divers. For obvious reasons this method of electro-fishing is banned due to the risk to the divers.

Stilts fishermen, Sri Lanka

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Recreational fishing and the closely related (nearly synonymous) sport fishing describe fishing for pleasure or competition. Recreational fishing has conventions, rules, licensing restrictions and laws that limit the way in which fish may be caught, The International Game Fishing Association (IGFA) makes and oversees these obligations. Typically, these prohibit the use of nets and the catching of fish with hooks not in the mouth.

The most common form of recreational fishing is done with a rod, line and hooks attached to any of a wide range of lures or baits. Most types of fishing tackle are made in a professional manufacturing facility and other for hobbyist enjoy making their own baits, examples would include the use of Fishing worm molds, etc. This practice is known as angling.

One method of growing popularity is kayak fishing. Kayak fisherman fish from sea kayaks in an attempt to level the playing field with fish and to further challenge their abilities. Kayaks are extremely stealthy and can allow anglers to reach areas unfishable from land or by conventional boat.

In angling, it is sometimes expected or required that fish all be returned to the water (catch and release). The practice, however, is viewed by some with disapproval as they consider it unethical to inflict pain on a fish for fun or sport and not for reasons of capturing food. Anglers deny this charge, pointing out that fish commonly feed on hard and spiky prey items, and as such can be expected to have tough mouths, and also that some fish will re-take a lure they have just been hooked on, a behavior that is unlikely if being hooked were painful. There is also some research that shows certain types of fish such as catfish, do not have nerves around their mouth. They most likely do not have nerves in their mouths due to the fact that they eat animals such as crawfish that can pinch.

In a real sense, the suitability of catch and release is an ethical consideration and, as such, a science-based conclusion on the issue is unavailable. Scientific studies show a wide range of survival, depending on species, environmental conditions, fish density and research design (methodology). The difficulty of doing such experiments is closely linked to the fact that negative effects of being exposed to fishing gears develop over a long time. Keeping fish trapped over a long period of time creates a lot of noise which makes it hard to single out the effect of the catch from the effect of the chosen methodology. Nevertheless, several studies have now returned very high survival rates (95%+) for species caught on fly and lures, which generally tend to hook fish in the mouth and thus aid catch and release fishing.

Proponents of catch and release also contend that the practice is increasingly necessary in order to conserve fish stocks in the face of burgeoning human populations, mounting fishing pressure and worsening habitat degradation. Opponents would prefer to ban or to severely restricting angling, a suggestion most anglers find unpalatable.

Recreational fishermen can have profound deleterious effects on fish stocks in commercial lakes, this is due to anglers with poor knowledge of how to protect the fish from damage or stress once out of the water. The fish which suffer most are those of large, slow growing species such as carp. The only way for growing numbers of recreational fishermen to continue fishing is to reduce their impact on fish populations or to increase the fish populations (e.g. by restocking). Catch and release, in combination with techniques such as strong tackle (to get fish in quickly, for release in good condition), careful handling of fish and barbless hooks (to reduce physical damage) and quick release lead systems such as the Korda quick release system or the E.S.P. variety may be useful tools in this endeavour.

Barbless hooks reduce damage to minimal levels, reduce de-hooking time and greatly aid in catch and release. Many keen catch and release anglers use barbless hooks. Barbless hooks can be purchased, or created by crushing the barbs on a normal hook flat with a pair of needle-nosed pliers. It is popularly believed barbless hooks lead to more lost fish, but ensuring lures are equipped with split rings and keeping the line tight while fighting fish will reduce fish losses to levels similar to those of barbed hooks. Also using circle hooks will cause the least amount of damage to a fish. The design of the hook is very simple, it is like a circle. When a fish bites the bait the hook's design causes it to hook in the side of the fish's mouth every time. This makes it very easy to remove the hook with minimal damage. Setting your hook when a fish bites is also different. Instead of snatching your line you slowly set your hook. This alone is a lot less stressful on the fish. A circle hook is the best choice for catch and release programs.

A recent phenomenon of recreational fishing are fishing competitions (tournaments) where fishermen compete for prizes based on the total weight of a given species of fish caught within a predetermined time. This sport evolved from local fishing contests into large competitive circuits, especially in North America. Competitors are most often professional fishermen who are supported by commercial endorsements. Other competitions is purely on length with mandatory catch and release, either longest fish or total length is documented with camera and a mandatory sticker, is more fair since it’s hard to weigh a living fish accurately in a boat.

Big-game fishing describes fishing from boats to catch large open-water species such as tuna, sharks and marlin.

Noodling and Trout tickling may be pursued as a recreation.

Laws made to control recreational fishing frequently also attempt to control the harvest of other aquatic species, such as frogs and turtles.

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A trawler leaving the port of Ullapool, north-west Scotland.

Commercial fishing provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions. Commercial fishermen harvest almost all aquatic species, from tuna, cod and salmon to shrimp, krill, lobster, clams, squid and crab, in various fisheries for these species. Commercial fishing methods have become very efficient using large nets and sea-going processing factories. Many new restrictions are often integrated with varieties of fishing allocation schemes (such as individual fishing quotas), and international treaties that have sought to limit the fishing effort and, sometimes, capture efficiency.

Fishing methods vary according to the region, the species being fished for, and the technology available to the fishermen. A commercial fishing enterprise may vary from one man with a small boat with hand-casting nets or a few pot traps, to a huge fleet of trawlers processing tons of fish every day.

Commercial fishing gears today are surrounding nets (e.g. purse seine), seine nets (e.g. beach seine), trawls (e.g. bottom trawl), dredges, hooks and lines (e.g. long line and handline), lift nets, gillnets, entangling nets and traps.

In addition to the above, commercial fishing can also be thought of as encompassing "pay to fish" enterprises, which provide anglers with controlled access to stocked lakes, ponds or canals. These provide fishing opportunities outside of the permitted seasons and quotas applied to public waters. In the United Kingdom, commercial fisheries of this sort charge access fees, with prices ranging from £2 to £25 per day. In North America, establishments usually charge for the fish caught, by length or by weight, rather than for access to the site although some establishments charge both types of fees. Prices for fish caught in North American "pay to fish" waters are generally in the range of $0.10 to $0.20 per cm or from $5.00 to $10.00 per kg.

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Video: COMMERCIAL FISHING OUTER BANKS 

Ancient methods of preserving fish included drying, salting, pickling and smoking. All of these techniques are still used today but the more modern techniques of freezing and canning have taken on a large importance.

See:

Haddock: Arbroath Smokie (lightly smoked).
Herring: kipper (salted and smoked), surströmming (fermented), rollmops (pickled), soused (salted).
Salmon: smoked salmon, cured salmon, and gravlax (fermented).
Cod: stockfish (air dried), lutefisk (soaked in lye).

In the past, fishing vessels were restricted in range by the simple consideration that the catch must be returned to port before it spoils and becomes worthless. The development of refrigeration and freezing technologies transformed the commercial fishing industry: fishing vessels could be larger, spending more time away from port and therefore accessing fish stocks at a much greater distance. Refrigeration and freezing also allow the catch to be distributed to markets further inland, reaching customers who previously would have had access only to dried or salted sea fish.

Canning, developed during the 19th century has also had a significant impact on fishing by allowing seasonal catches of fish that are possibly far from large centres of population to be exploited. For example: sardines.

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Fried fish & French fries (fish & chips)

Food

The flesh of many fish are primarily valued as a source of food; there are many edible species of fish as well as other sea food.

Shellfish include shelled molluscs and crustaceans used as food. Shelled molluscs include the clam, mussel, oyster, winkle and scallop; some crustaceans are the shrimp, lobster, crayfish, and crab.

Eggs, called roe, of various species may be eaten; roe comes from fish and certain marine invertebrates, such as sea urchins and shrimp. In some cultures, roe is considered a delicacy, for example caviar from the sturgeon.

Squid and octopus are valued as food.

Sea cucumber is considered a delicacy in Chinese cooking and is often served at New Year’s feasts, usually in soups.^[1]

In some cultures, for example China, Japan, and Vietnam, certain species of jellyfish are consumed.^[2]

Fish oil is valued as a dietary supplement.

Korean style raw fish.

Live fish

Live fish are collected for the international live food fish trade. Some seafood restaurants keep live fish in aquaria for display or for cultural beliefs. The majority of live fish kept at seafood restaurants, however, are desired for the freshness of the seafood, being killed only immediately before being cooked. Suiting customer preference, this practice makes the seafood higher in quality and better in taste. The prevalence of cultural beliefs and consumer standards helps to drive the demand for the live food fish trade. Hong Kong, for example, is estimated to have imported in excess of 15,000 tonnes of live food fish in 2000. This brought the value of their live food fish trade industry to US$400 million as reported by the World Resources Institute.^[3]

Fish can also be collected in ways that do not injure them such as in a seine net or by placing an electric current into the water. Such techniques are used most often by researchers for observation and study but are also used by those who collect fish for the aquarium trade. There are several organizations devoted to improving the methods of collecting, handling, transporting, exporting and farming of wild and domesticated live food fish, as well as freshwater and marine tropical fish destined for aquaria.

Other products

Pearls and mother-of-pearl are valued for their lustre. Traditional methods of pearl hunting are now virtually extinct.

Sharkskin and rayskin which are covered with, in effect, tiny teeth (dermal denticles) were used for the purposes that sandpaper currently is. These skins are also used to make leather. Sharkskin leather is used in the manufacture of hilts of traditional Japanese swords.

Sea horse, star fish, sea urchin and sea cucumber are used in traditional Chinese medicine.

Tyrian purple is a pigment made from marine snails Murex brandaris and Murex trunculus.

Sepia is a pigment made from the inky secretions of cuttlefish.

Fish glue is made by boiling the skin, bones and swim bladders of fish. Fish glue has long been valued for its use in all manner of products from illuminated manuscripts to the Mongolian war bow.

Isinglass is a substance obtained from the swim bladders of fish (especially sturgeon), it is used for the clarification of wine and beer.

Fish emulsion is a fertilizer emulsion that is produced from the fluid remains of fish processed for fish oil and fish meal industrially.

Cooked mussels

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The fishing industry is the commercial activity of fishing and producing fish and other seafood products for human consumption or as input factors in other industrial processes. According to Food and Agriculture Organization (FAO) statistics the total fish production in the world in 2001 was 130 million tonnes. In addition to the commercial catches, 37.9 million tonnes were produced in aquaculture plants.

In the 1990s and 2000s it has become increasingly evident that industrial fishing has severely depleted stocks of certain types of ocean fish, such as cod. For more information, see overfishing.

One fishing industry sector that appears to remain in a good state of production is the freshwater fishing sector in Canada. The Manitoba commercial fishing industry is comprised of over 3,600 fisherpersons who produce 25 percent of Canada's freshwater catch. Lake Winnipeg is the biggest contributor of commercially landed fish species. Of the 13 fish species commercially harvested, pickerel (walleye), Sauger, lake whitefish, northern pike, yellow perch and lake trout are the most highly valued species. Others include white sucker, tullibee, carp, burbot, lake sturgeon, Goldeye and white bass.

Links

• Freshwater Commercial Fishing on Lakes
• FAO Fisheries Information
• Fish database (FishBase)
• Alaska Commercial Fishing News
• American Fisheries Society
• One Fish
• NOAA Fisheries Service

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The hobby can be broadly divided into three specific disciplines, freshwater, brackish, and marine (also called saltwater) fishkeeping. Freshwater fishkeeping is by far the most popular branch of the hobby, with even small pet stores often selling a variety of freshwater fish, such as goldfish, guppies, and angelfish. While most freshwater aquaria are set up as community tanks containing a variety of peaceful species, many aquarists keep single-species aquaria with a view to breeding. Livebearing fish such as mollies and guppies are among the species that are most easily raised in captivity, but aquarists also regularly breed numerous other species, including many types of cichlid, catfish, characin, and killifish.

Marine aquaria are generally more difficult to maintain and the livestock is significantly more expensive, and as a result this branch of the hobby tends to attract more experienced fishkeepers. However, marine aquaria can be exceedingly beautiful, due to the attractive colours and shapes of the corals and coral reef fish kept in them. Temperate zone marine fish are not as commonly kept in home aquaria, primarily because they do not do well at room temperature. An aquarium containing these coldwater species usually needs to be either located in a cool room (such as an unheated basement) or else chilled using a refrigeration device known as a 'chiller'.

Brackish water aquaria combine elements of both marine and freshwater fishkeeping, reflecting the fact that these aquaria contain water with a salinity in between that of freshwater and seawater. Fish kept in brackish water aquaria come from habitats with varying salinity, such as mangroves and estuaries and do not do well if permanently kept in freshwater aquaria. Although brackish water aquaria are not overly familiar to newcomers to the hobby, a surprising number of species prefer brackish water conditions, including the mollies, many gobies, some pufferfish, monos, scats, and virtually all the freshwater soles.

Fishkeepers are often known as aquarists, since many of them are not solely interested in keeping fish. Many fishkeepers create freshwater aquaria where the focus is on the aquatic plants rather than on the fish. Though known as the 'Dutch Aquarium' in some circles, in reference to the pioneering work carried out by European aquarists in designing these sorts of aquaria. In recent years, one of the most active advocates of the heavily planted aquarium is the Japanese aquarist Takashi Amano. Marine aquarists very often attempt to recreate the coral reef in their aquaria using large quantities of living rock, porous calcareous rocks encrusted with algae, sponges, worms, and other small marine organisms. Larger corals as well as shrimps, crabs, echinoderms, and molluscs are added later on, once the aquarium has matured, as well as a variety of small fish. Such aquaria are sometimes called 'reef tanks'.

Garden ponds are in some ways similar to freshwater aquaria, but are usually much larger and exposed to the ambient climatic conditions. In the tropics, tropical fish can be kept in garden ponds, but in the cooler regions temperate zone species such as goldfish, koi, and orfe are kept instead.

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Koi have been kept in decorative ponds for centuries in China and Japan.

The origins of fishkeeping

Fish have been raised as food in pools and ponds for thousands of years. In Medieval Europe, carp pools were a standard feature of estates and monasteries, providing an alternative to meat on feast days when meat could not be eaten for religious reasons. Similarly, throughout Asia there is a long history of stocking rice paddies with freshwater fish suitable for eating, including various types of catfish and cyprinid. Particularly brightly coloured or tame specimens of fish in these pools have sometimes been valued as pets rather than food, and some of these have given rise to completely domesticated varieties, most notably the goldfish and the koi carp, which have their origins in China and Japan respectively.

Marine fish have been similarly valued for centuries, and many wealthy Romans kept lampreys and other fish in salt water pools. Cicero reports that the advocate Quintus Hortensius wept when a favoured specimen died, while Tertullian reports that Asinius Celer paid 8000 sesterces for a particularly fine mullet.[1]

Modern fishkeeping

Although some tropical fish were kept in gas-heated tanks in Victorian times, tropical fishkeeping only really became popular from the 1930s onwards when devices like electric heaters and inexpensive glass aquaria became available. Air transportation has also made it possible for fish to be imported from many parts of the world rapidly and inexpensively. As a result, aquarists are routinely offered large numbers of freshwater fish collected from South America, South East Asia, and East Africa. However, the majority of freshwater fish sold to aquarists are commercially bred, primarily in South East Asia and Florida.

Marine fish are not easily bred in captivity, and only a few species, most notably seahorses and clownfish are farm-raised. Most are collected from coral reefs, in particular from South East Asia, the Red Sea, and the Caribbean.

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Worldwide, the fishkeeping hobby is a multi-million dollar industry, and the United States is considered the largest market in the world, followed by Europe and Japan. In 1994, 56% of U.S. households had pets, and 10.6% owned ornamental freshwater or saltwater fish, with an average of 8.8 fish per household. In 1993, the retail value of the fish hobby in the United States was $910 million.

From 1989 to 1992, almost 79% of all U.S. ornamental fish imports arrived from Southeast Asia and Japan. Singapore, Thailand, the Philippines, Hong Kong, and Indonesia were the top five exporting nations. South America was the second largest exporting region, accounting for 14% of the total annual value. Colombia, Brazil, and Peru were the major suppliers. The remaining 7% of ornamental fish imports came from other regions of the world.

Approximately 201 million fish worth $44.7 million were imported into the United States in 1992. These fish comprised 1,539 different species; 730 freshwater species, and 809 saltwater species. The freshwater fish accounted for approximately 96% of the total volume and 80% of the total import value. Of the total of all trade, only 32 species had import values over $10,000. These top species were all of freshwater origin and accounted for 58% of the total imported value of the fish. The top imported species are the guppy, neon tetra, platy, betta, Chinese algae eater, and goldfish.

Several large companies are focused primarily or extensively on supplying the fishkeeping hobby, producing products such as fish food, medicine, and aquarium hardware. Among the largest of these are Eheim, Tetra, Sera, all based in Germany; Hikari, a Japanese company; Fluval, part of the Canadian Rolf C. Hagen group; Interpet, a British company that also owns the Red Sea brand; and the American company Aquarian, owned by Mars, Incorporated but usually trading under the Waltham petfoods brand.

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A Discus (Symphysodon spp.) guarding its eggs

Fish breeding is a challenge that many aquarists find attractive. While some species reproduce freely in community tanks, most require special conditions, known as spawning triggers before they will breed. The majority of fish lay eggs, known as spawning and the juvenile fish that emerge are very small and need tiny live foods or their substitutes to survive. A fair number of popular aquarium fish are livebearers, and these fish produce small number of relatively large offspring, and these will usually take ground flake food straight away.

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According to the FAO, at least 90% of freshwater aquarium fish are captive bred [1]. Nearly all marine ornamental fish are wild-caught 2]. Fish are collected from the wild could provide a valuable source of income for people in regions where other high-value exports may be lacking [3]. Catching fish in the wild could also reduce their population sizes, placing them in danger.

In theory, wild fish should be a good example of a renewable resource that places value on maintaining the integrity and diversity of the natural habitat: more and better fish can be exported from clean, pristine aquatic habitat than one that has been polluted or otherwise degraded. However, this has not been the case with industries such as fur trapping, logging, or fishing where a similar situation existed. Historically, wild resources have tended to be overexploited rather than managed (see Tragedy of the Commons). Moreover, in places where collecting for aquaria is very intensive, there is good evidence that collecting can result in a decline in fish populations. A particular notorious example is to be found on the Philippines, where overfishing and the widespread use of cyanide to stun the fish has caused a drastic decline in the diversity of the coral reef fish considered most desirable by aquarists [4].

On the other hand, breeding programs by aquarists have helped to preserve species that have become rare or extinct in the wild, most notably among the Lake Victoria cichlids. Some species of aquarium fish have also become important as laboratory animals, with cichlids and poecilids being especially important for studies on learning, mating, and social behaviour. Aquarists also observe a large number of fishes not otherwise studied, and thereby provide valuable data on the ecology and behaviour of many species.

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At its best, a properly maintained aquarium allows the fish to socialise with their own kind and in many cases breed successfully. This is in marked contrast to the conditions enjoyed by larger animals like cats and dogs, which are often kept alone and neutered, and thus unable to experience anything like a natural lifestyle. However, in many cases fish are maintained in the wrong conditions and therefore live short lives and never breed. Inexperienced aquarists often attempt to keep too many fish in their tanks, or introduce too many fish into an immature aquarium, with the result that large numbers of fish sicken and die. This has given the hobby a bad reputation among some animal welfare groups, such as PETA, for treating aquarium fish as nothing more than cheap toys that are simply replaced when they die [6].

Marine fish in particular tend to be less resilient during transportation than freshwater fish, and relatively large numbers of them die before they are finally sold to the aquarist. Although the trade in marine fish and corals for aquaria probably represents a minor threat to coral reefs when compared with habitat destruction, fishing for food, and climate change, it is a booming trade and may be a serious problem in specific locations such as the Philippines and Indonesia where most of the collecting is done [7], [8].

Goldfish and bettas in particular have often been kept in cramped bowls or aquaria that are really far too small for their needs [9]. In some cases fish have been installed in all sorts of inappropriate objects such as the AquaBabies Micro Aquaria, Bubble Gear Bubble Bag and Betta in a Vase, all of which contain live fish housed in unfiltered and entirely too small quantities of water [10], [11]. The Betta in a Vase is sometimes marketed as a complete ecosystem if a plant is included in the neck of the vase, some sellers claiming the fish will eat the roots of the plant. However, bettas are carnivorous and need to be fed live food or pellet foods as they cannot survive on plant roots. Another problem is if the plant blocks the bettas passage to the water surface, as they are labyrinth fishes, and need to be able to take breaths at the surface of the water or else they will die from suffocation. These types of products are not really aimed at aquarists but rather at people looking for a novelty gift, and in fact most aquarists abhor them. Similarly, the awarding of goldfish as prizes at funfairs is traditional in many parts of the world, but has been criticised by aquarists and animal welfare charities alike as cruel and irresponsible, and giving away live-animal prizes such as goldfish was made illegal in the UK in 2004 [12].

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Modifying fish to make them more attractive as pets is an increasingly divisive issue. Historically, artificially dyeing fish was fairly common, with glassfish for example being injected with fluorescent dyes. The major British fishkeeping magazine, Practical Fishkeeping, has been effective in its campaign to remove these fish from the market by educating retailers and aquarists to the cruelty and health risks involved [1].

In 2006, Practical Fishkeeping published an article exposing the techniques for performing cosmetic surgery on aquarium fish, without anaesthetia, as described by Singaporean fishkeeping magazine Fish Love Magazine. The tail is cut off and dye is injected into the body to make the fish more valuable [2]. The piece also included the first documented evidence to demonstrate that parrot cichlids are dyed through injections of coloured dye. Practical Fishkeeping also reported in 2006 that suppliers in Hong Kong were offering a service in which fish could be tattooed with company logos or messages using a dye laser [3]. Such fishes have been sold in the UK under the name of Kaleidoscope gourami and Striped parrot cichlid.

Hybrid fish such as flowerhorn cichlids and parrot cichlids are highly controversial. Parrot cichlids in particular have a very unnatural shape that prevents them from swimming properly and makes it difficult for them to engage in their normal feeding and social behaviours. The biggest concern with hybrids is that they may be bred back with true species, making it difficult for hobbyists to identify and breed particular species. This is especially important where hobbyists are conserving species that are rare or extinct in the wild [4]. Even within a single species, extreme mutations have been selected for by some breeders; some of the fancy goldfish varieties in particular have been criticised for having features that prevent the fish from swimming, seeing, or feeding properly. Genetically modified fish like the glofish are likely to become increasingly available as well, particularly in the United States [5], [6].

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Agnatha 
Fossil range: Early Cambrian - Recent  
Scientific classification
Kingdom: Animalia
Phylum: Chordata 
Subphylum: Vertebrata 
Superclass: Agnatha 
Groups
Myxini (hagfish)
Hyperoartia: Petromyzontidae (lampreys)
Pteraspidomorphi
Thelodonti
Anaspida
Cephalaspidomorphi: Galeaspida, Pituriaspida, Osteostraci

Agnatha (Greek, "no jaws") is a paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. There are two extant groups of jawless fish (sometimes called cyclostomes), the lampreys and the hagfish, with about 60 species between them. In addition to the absence of jaws, Agnatha are characterised by absence of paired fins; the presence of a notochord both in larvae and adults; and seven or more paired gill pouches. The branchial arches supporting the gill pouches lies close to the body surface. There is a light sensitive pineal eye (homologous to the pineal gland in mammals). There is no identifiable stomach. Fertilization is external. The Agnatha are ectothermic, with a cartilaginous skeleton, and the heart contains 2 chambers.

Although they are superficially similar, many of these similarities are probably shared primitive characteristics of ancient vertebrates, and modern classifications tend to move the hagfish into a separate group (the Myxini or Hyperotreti), with the lampreys (Hyperoartii) being more closely related to the jawed fishes.

Fossil agnathans

Haikouichthys is a fossil agnathan.

Cephalaspis is another fossil agnathan.

Although a minor element of modern marine fauna, Agnatha were prominent among the early fish in the early Paleozoic. Two types of Early Cambrian animal apparently having fins, vertebrate musculature, and gills are known from the early Cambrian Maotianshan shales of China: Haikouichthys and Myllokunmingia. They have been tentatively assigned to Agnatha by Janvier. A third possible agnathid from the same region is Haikouella. A possible agnathid that has not been formally described was reported by Simonetti from the Middle Cambrian Burgess Shale of British Columbia.

Many Ordovician, Silurian, and Devonian agnathans were armored with heavy bony plates. The first armored agnathans—the Ostracoderms, precursors to the bony fish and hence to the tetrapods (including human beings)—are known from the middle Ordovician, and by the Late Silurian the agnathans had reached the high point of their evolution. Agnathans declined in the Devonian and never recovered.

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Video: Worlds deepest living fishes survives under pressure

Gnathostomata  Fossil range: Late Ordovician - Recent
Gnathostomata are jawed vertebrates
Scientific classification
Kingdom: Animalia   Phylum: Chordata   Subphylum: Vertebrata   Infraphylum: Gnathostomata
Classes
Placodermi Chondrichthyes Acanthodii Actinopterygii Sarcopterygii

Gnathostomata is the group of vertebrates with jaws.

The group is traditionally a superclass, including the familiar classes of fish, birds, and so forth, and a sister group of the jawless vertebrates Agnatha. However, recent genetic studies are causing a reassessment of Gnathostomata as a grouping.

It is assumed the jaws evolved from anterior gill support arches that had acquired a new role, being modified to pump water over the gills by opening and closing the mouth more effectively. The mouth could then grow bigger and wider, making it possible to capture small prey. This close and open mechanism would with time become stronger and tougher, being transformed into real jaws. Modified dermal bones on the surface of the skin would migrate into the mouth and become primtive teeth. Placoderms used sharp bony plates as teeth instead.

Other distinguishing characteristics of living gnathostomates are the myelin sheathes of neurons, and an adaptive immune system.

Taxonomy & Phylogeny

Subphylum Vertebrata
├─(unranked) Gnathostomatomorpha
└─Infraphylum Gnathostomata
      ├─Class Placodermi - extinct (armored gnathostomes)
      └Microphylum Eugnathostomata (true jawed vertebrates)
         ├─Class Chondrichthyes (cartilagenous fish)
         └(unranked) Teleostomi (Acanthodii & Osteichthyes)
             ├─Class Acanthodii - extinct ("spiny sharks")
             └Superclass Osteichthyes (bony fish)
                 ├─Class Actinopterygii (ray-finned fish)
                 └─Class Sarcopterygii (lobe-finned fish)
                    └Superclass Tetrapoda
                        ├─Class Amphibia (amphibians)
                        └(unranked) Amniota (amniotic egg)
                            ├─Class Sauropsida (reptiles or sauropsids)
                            │           └─Class Aves (birds)
                            └Class Synapsida
                                └─Class Mammalia (mammals)

Note lines show evolutionary relationships.

Links

• Tree of Life discussion of Gnathostomata
• The Gill Arches: Meckel's Cartilage

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.

Fossil range: Latest Ordovician to Early Permian 
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Class: Acanthodii
Orders: Climatiiformes, Ischnacanthiformes, Acanthodiformes

Acanthodii (sometimes called spiny sharks) is a class of extinct fishes, having features of both bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes). They appeared in the early Silurian (430 mya) and lasted until the late Permian (250 mya). The earliest ancanthodians were marine, but during the Devonian, freshwater species became predominant. They are distinguished in two respects: they were the first known jawed vertebrates, and they had stout spines supporting their fins, fixed in place and non-movable (like a shark's dorsal fin).

There were three orders: Climatiiformes, Ischnacanthiformes and Acanthodiformes. Climatiiforma had shoulder armor and many small sharp spines, Ischnacanthiforma with teeth fused to the jaw, and the Acanthodiforma were filter feeders, with no teeth in the jaw, but long gill rakers.

Almost all of them were small, slender fish with large eyes, heterocercal tails, with the caudal vertebrae supporting the top lobe of the tail fin, like a shark's tail has today. All had pairs of bony spines along the ventral mid-body line, that often supported a web of tissue between the spine and the body, creating a fin. Thus the "spiny shark" nickname. These distinctive spines give the class its name, from the Greek akanthos.

The scales of Acanthodii are unique and used in determining relative age of sedimentary rock. The scales are tiny, with a bulbous base, a neck, and a flat or slightly curved diamond-shaped crown.

References

• Long, J.A. The Rise of Fishes: 500 Million Years of Evolution. Johns Hopkins Univ. Press. Baltimore and London. 1995.

Links

• Acanthodii taxonomy
• †Ischnacanthiformes taxonomy
• †Climatiiformes taxonomy
• †Acanthodiformes taxonomy
• Ischnacanthus gracilis - A Devonian Fish by Neal Robbins
• PALAEOZOIC FISH UK
• Acanthodopsis wardi

This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.