An electric fish is a fish that can generate electric field

Electric field

In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

s. It is said to be electrogenic; a fish that has the ability to detect electric fields is said to be electroreceptive. Most electrogenic fish are also electroreceptive. Electric fish species can be found both in the sea and in freshwater rivers of South America (Gymnotiformes

Gymnotiformes

The Gymnotiformes are a group of teleost bony fishes commonly known as the Neotropical or South American knifefishes. They have long bodies and swim using undulations of their elongated anal fin...

) and Africa (Mormyridae

Mormyridae

The family Mormyridae, sometimes called "elephantfish" , are freshwater fish in the order Osteoglossiformes native to Africa. It is by far the largest family in the order with around 200 species. Members of the family are popular, if challenging, aquarium species...

). Many fish such as shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s, rays and catfish

Catfish

Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

es 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 kept in aquaria

Aquarium

An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...

 or caught for food, are neither electrogenic nor electroreceptive.

Strongly and weakly electric fish

Electric fish produce their electrical fields from a specialized structure called an electric organ

Electric organ

In biology, the electric organ is an organ common to all electric fish used for the purposes of creating an electric field. The electric organ is derived from modified nerve or muscle tissue...

. This is made up of modified muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 or nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

 cells, which became specialized for producing bioelectric fields stronger than those that normal nerves or muscles produce (Albert and Crampton, 2006). Typically this organ is located in the tail of the electric fish. The electrical 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

Amplitude

Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...

 of the signal can range from 10 to 500 Volt

Volt

The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...

s with a current of up to 1 Ampere

Ampere

The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...

. Typical examples are the electric eel

Electric eel

The electric eel , is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks, of up to six hundred volts, which it uses for both hunting and self-defense. It is an apex predator in its South American range...

 (Electrophorus electricus; not a true eel but a knifefish

Knifefish

Knifefish may refer to several knife-shaped fishes:* The Neotropical or weakly electric knifefishes, order Gymnotiformes, containing five families:** Family Gymnotidae ** Family Rhamphichthyidae...

), the electric catfish

Electric catfish

Electric catfish is the common name for the catfish family Malapteruridae. This family includes two genera, Malapterurus and Paradoxoglanis with 19 species. Several species of this family have the ability to produce an electric shock of up to 350 volts using electroplaques of an electric organ...

es (family Malapteruridae), and electric ray

Electric ray

The electric rays are a group of rays, flattened cartilaginous fish with enlarged pectoral fins, comprising the order Torpediniformes. They are known for being capable of producing an electric discharge, ranging from as little as 8 volts up to 220 volts depending on species, used to stun prey and...

s (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)

Electroreception

Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...

 and communication with other electric fish (electrocommunication). Some of the best known and most studied examples are Peters' elephantnose fish

Peters' elephantnose fish

Peters' elephantnose fish is an elephantfish in the genus Gnathonemus. Other names in English include elephantnose fish, long-nosed elephant fish, and Ubangi mormyrid, after the Ubangi River...

 (Gnathonemus petersi) and the black ghost knifefish

Black ghost knifefish

The black ghost knifefish, Apteronotus albifrons, is a tropical fish belonging to the ghost knifefish family . They originate in South America in the Amazon Basin in Peru and from Venezuela through Paraguay in the Paraná River. They are becoming popular in aquaria...

 (Apteronotus albifrons).

The EOD waveform takes two general forms depending on the species. In some species the waveform is continuous and almost sinusoidal

Sine wave

The sine wave or sinusoid is a mathematical function that describes a smooth repetitive oscillation. It occurs often in pure mathematics, as well as physics, signal processing, electrical engineering and many other fields...

 (for example the genera Apteronotus

Apteronotus

Apteronotus is a genus of weakly electric knifefish in the family Apteronotidae, distinguished by the presence of a tiny caudal fin.-Species:* Black ghost knifefish, Apteronotus albifrons ....

, 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

Gnathonemus

Gnathonemus is a genus of elephantfish in the family Mormyridae.- Species :* Gnathonemus barbatus Poll, 1967* Gnathonemus echidnorhynchus Pellegrin, 1924...

, Gymnotus

Gymnotus

Gymnotus is the among the most species-rich group of electric knifefishes found in the Amazon. Some Gymnotus species live in the leaf litter and root tangles of river banks. Other species are specialized to live on floodplains within the rootmats of floating meadows. Several species are broadly...

, Raja

Raja (genus)

Raja is a genus of skates in the family Rajidae, containing nearly thirty species. They are flat-bodied cartilaginous fish with a rhombic shape due to their large pectoral fins extending from or nearly from the snout to the base of their tail. Their sharp snouts produced by a cranial projection of...

) and these are said to have a pulse-type EOD.

Table of electric fish

Following is a table of all known electric fish species within fresh water. There are two groups of marine fishes, the electric rays (Torpediniformes: Narcinidae and Torpedinidae) and the stargazers (Perciformes: Uranoscopidae) capable of generating strong electric pulses.

Taxon	Species (348)
Gymnotiformes Gymnotiformes The Gymnotiformes are a group of teleost bony fishes commonly known as the Neotropical or South American knifefishes. They have long bodies and swim using undulations of their elongated anal fin...
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 Orthosternarchus tamandua Orthosternarchus tamandua is a species of weakly electric knifefish in the family Apteronotidae, native to the deep river channels of the Amazon River system. It is the only species in its genus. This species is characterized by its long tubular snout, long dorsal appendage, and tiny, bilaterally... , Parapteronotus hasemani, Platyurosternarchus macrostomus, Porotergus gimbeli, Porotergus gymnotus, Sternarchella curvioperculata, Sternarchella orthos, Sternarchella schotti Sternarchella schotti Sternarchella schotti is a species of weakly electric knifefish in the family Apteronotidae. This species is found in the Amazon River basin, and is sometimes kept in aquaria. The species grows to approximately 20 cm in length, and has a pale pink color in life with brown speckling along the... , Sternarchella sima, Sternarchella terminalis, Sternarchogiton nattereri Sternarchogiton nattereri Sternarchogiton nattereri is a species of weakly electric knifefish in the family Apteronotidae. It is native to the Amazon River system and feeds on sponges. Unlike other members of the genus Sternarchogiton, there is pronounced sexual dimorphism in S. nattereri, with reproductively mature males... , Sternarchogiton porcinum Sternarchogiton porcinum Sternarchogiton porcinum is a species of weakly electric knifefish in the family Apteronotidae. It is native to deep river channels in the Río Huallaga, Río Napo, and Río Amazonas in Peru, and in the Río Orinoco in Venezuela. Many specimens once identified as S. porcinum from the Brazilian Amazon... , 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 Hypopomidae Hypopomidae is a family of fishes in the order Gymnotiformes known as the bluntnose knifefish. They may also be called grass or leaf knifefishes... (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 Rhamphichthyidae Sand knifefishes are freshwater fishes of the Rhamphichthyidae family, from South America. There are only 3 genera and around 15 species in this group.... (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 Osteoglossiformes Osteoglossiformes is a relatively primitive order of ray-finned fish that contains two sub-orders, the Osteoglossoidei and the Notopteroidei. All of the living species inhabit freshwater...
Gymnarchidae (1 species in 1 genus)	Gymnarchus niloticus Gymnarchus niloticus Gymnarchus niloticus – commonly known as the aba, aba aba, frankfish, freshwater rat-tail or African knifefish – is an electric fish, and the only species in the genus Gymnarchus and the family Gymnarchidae within the order Osteoglossiformes...
Mormyridae Mormyridae The family Mormyridae, sometimes called "elephantfish" , are freshwater fish in the order Osteoglossiformes native to Africa. It is by far the largest family in the order with around 200 species. Members of the family are popular, if challenging, aquarium species... (203 species in 18 genera)	Boulengeromyrus knoepffleri Boulengeromyrus knoepffleri Boulengeromyrus knoepffleri is a species of elephantfish in the family Mormyridae being the only member of its genus. It occurs only in the Ivindo River and the Ntem River basins of Gabon and Cameroon in Africa. It reaches a length of about 41 cm.... , 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 Genyomyrus donnyi Genyomyrus donnyi is a species of elephantfish in the family Mormyridae being the only member of its genus. It occurs only in the central Congo River basin in Africa. It reaches a length of about 45 cm.... , Gnathonemus barbatus, Gnathonemus echidnorhynchus, Gnathonemus longibarbis, Gnathonemus petersii, Heteromormyrus pauciradiatus Heteromormyrus pauciradiatus Heteromormyrus pauciradiatus is a species of elephantfish in the family Mormyridae being the only member of its genus. It is found only in the coastal river basins in Angola in Africa. It reaches a length of about 10 cm.... , 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 Isichthys henryi Isichthys henryi is a species of elephantfish in the family Mormyridae being the only member of its genus. It occurs in river basins along the central-western coast of Africa. It reaches a length of about 29 cm.... , Ivindomyrus opdenboschi Ivindomyrus opdenboschi Ivindomyrus opdenboschi is a species of elephantfish in the family Mormyridae being the only member of its genus. It is only found in the Ivindo River in Gabon, Africa. It reaches a length of about 27 cm.... , 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 livingstonii Marcusenius livingstonii is a species of fish in the Mormyridae family. It is found in Malawi, Mozambique, and Tanzania. Its natural habitats are rivers, intermittent rivers, and freshwater lakes. It is threatened by habitat loss.-References:... , 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 caschive Mormyrus caschive is a species of fish in the Mormyridae family. It is endemic to Uganda. Its natural habitat is freshwater lakes.-References:* Twongo, T.K. 2005. . Downloaded on 4 August 2007.... , Mormyrus cyaneus, Mormyrus felixi, Mormyrus goheeni, Mormyrus hasselquistii, Mormyrus iriodes, Mormyrus kannume, Mormyrus lacerda, Mormyrus longirostris, Mormyrus macrocephalus Mormyrus macrocephalus Mormyrus macrocephalus is a species of fish in the Mormyridae family. It is endemic to Uganda. Its natural habitats are rivers and freshwater lakes.-References:* Twongo, T.K. 2005. . Downloaded on 4 August 2007.... , 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 beninensis Malapterurus beninensis is a species of catfish of the family Malapteruridae.... , Malapterurus cavalliensis Malapterurus cavalliensis Malapterurus cavalliensis is a species of catfish of the family Malapteruridae.... , Malapterurus electricus, Malapterurus leonensis Malapterurus leonensis Malapterurus leonensis is a species of catfish of the family Malapteruridae.... , Malapterurus microstoma, Malapterurus minjiriya, Malapterurus monsembeensis Malapterurus monsembeensis Malapterurus monsembeensis is a species of catfish of the family Malapteruridae.... , Malapterurus oguensis Malapterurus oguensis Malapterurus oguensis is a species of catfish of the family Malapteruridae.... , Malapterurus shirensis Malapterurus shirensis Malapterurus shirensis is a species of catfish of the family Malapteruridae.... , Malapterurus tanganyikaensis Malapterurus tanganyikaensis Malapterurus tanganyikaensis is a species of catfish of the family Malapteruridae.... , Malapterurus tanoensis Malapterurus tanoensis Malapterurus tanoensis is a species of catfish of the family Malapteruridae....
Perciformes Perciformes The Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments...
Uranoscopidae (50 species in 8 genera)	Astroscopus guttatus, Astroscopus y-graecum, Astroscopus zephyreus, Gnathagnus egregius, Kathetostoma albigutta, Kathetostoma averruncus

External links

• Electric Fish, Mark E. Nelson, Beckman Institute Neuroscience Program, University of Illinois at Urbana-Champaign
  University of Illinois at Urbana-Champaign
  The University of Illinois at Urbana–Champaign is a large public research-intensive university in the state of Illinois, United States. It is the flagship campus of the University of Illinois system...
  
  , Accessed 11/2006, http://nelson.beckman.uiuc.edu/electric_fish.html
• Article at CWRU
• Electric Fish Advertise Their Bodies - Male fish can amp up their electric fields to woo females and intimidate rivals, LiveScience.com, 29 February 2008