7 Types of Electric Fish and How They Generate Their Shocking Power
October 27, 2026
Of the more than 30,000 fish species swimming in the world’s oceans and rivers, only around 350 can generate their own electric fields. ScienceDirect’s overview of electric fish biology notes that strongly electric fish use electricity to stun their prey, while weakly electric fish use electricity for sensing and communication. That single distinction explains almost everything odd and wonderful about the many types of electric fish alive today.
Some of these fish can drop a horse with a single jolt. Others produce a current so faint you would never feel it, yet it lets them “see” in pitch-black water using nothing but their own bioelectric field. This rundown of electric fish species covers seven of the most remarkable examples, from South American river giants to African elephantfish, and explains what each one does with its built-in power supply.
1. Electric Eel
The electric eel is the poster child for strongly electric fish, and for good reason. Despite the name, the electric eel is not a true eel at all. Despite their name, electric eels are not closely related to the true eels (Anguilliformes) but are members of the electroreceptive knifefish order, Gymnotiformes, an order more closely related to catfish. Its scientific genus, Electrophorus electricus, was believed to be monotypic for more than two centuries before researchers split it into three species in 2019.
Electric eels live in the muddy, shaded river bottoms of the Orinoco and Amazon basins, and inhabit muddy river bottoms with dense vegetation and plenty of shade in South America, particularly the Orinoco River basin and parts of the Amazon. They are also unusual among fish in how they breathe: unlike other fish, the electric eel gets most of its oxygen by breathing in air from the surface.
What makes the electric eel special is that it produces two entirely different signals from the same body. A weak, low-voltage discharge handles everyday electrolocation, while a separate high-voltage system is reserved for hunting and defense. The low-voltage output comes at a low rate in a resting eel but may be emitted at 10-20 Hz when the eel is excited and hunting, while the high-voltage EOD is far stronger and is emitted at rates of up to 500 Hz. That high-voltage volley can be devastating: an approaching eel elicits a C-start escape response in a goldfish, but the goldfish is immobilized by a volley of high-voltage pulses and captured within 200 ms.
Just how strong is that shock? Reports on the genus put the maximum at delivering shocks at up to 860 volts, which is why researchers who study electric organs and how they evolved describe eels as an extreme case among electrogenic fish. For a closer look at the mechanics behind this, the explainer on how electric fish generate electricity breaks down the electrocyte structures responsible.
Pro Tip: Researchers studying electric eels typically avoid direct contact entirely rather than relying on gloves, since a startled eel can fire repeated high-voltage volleys strong enough to injure a person standing in shallow water.
Scientists have also traced the genetic switch behind this ability. A National Science Foundation-funded study found that all fish have duplicate versions of the sodium channel gene that produces tiny muscle switches, and to evolve electric organs, electric fish turned off one duplicate of the gene in muscles and turned it on in other cells. That small genetic tweak is what separates an electric eel from an ordinary knifefish cousin.
2. Electric Ray (Torpedo Fish)
Move from freshwater to the open ocean and the electric ray, or torpedo fish, takes over as the marine equivalent of the electric eel. These rays belong to the Torpedo genus, and the marine electric ray, genus Torpedo, is capable of generating powerful electrical discharges that can be measured in the water surrounding it.
The Common Torpedo is one well-documented species within this group. Its coloration ranges from grayish-brown to reddish-brown, and it often has darker spots or scars on its body. According to one voltage comparison of electric species, a Torpedo Ray can generate about 220 volts, a discharge strong enough to stun fish many times its own size.
Torpedo rays use a wave-type discharge rather than a series of short pulses. Electric organ discharges need to vary with time for electrolocation, whether with pulses, as in the Mormyridae, or with waves, as in the Torpediniformes and Gymnarchus, the African knifefish. That wave-based system, combined with the ray’s size, is what makes it dangerous to handle carelessly. Divers who encounter one accidentally sometimes describe a defensive reaction not unlike brushing against a stinging jellyfish species, except the electric ray’s response is a deliberate discharge rather than a passive sting.
3. Electric Catfish
Africa’s contribution to the strongly electric fish club is the electric catfish, genus Malapterurus. This freshwater fish, found in African habitats, is one of the classic examples of a strongly electric species alongside the South American electric eel. Unlike the eel’s tail-based organ, the catfish’s electric tissue wraps around most of its body. An electric catfish’s electric organ forms a sheath around much of the body, which is why a single contact can deliver a shock over a large surface area rather than from one localized point.
People have known about this fish’s power for a very long time. Detailed descriptions of the powerful shocks that the electric catfish could give were written in ancient Egypt, making it one of the earliest documented electric animals in human history, long before anyone understood electricity as a physical force.
Like other strongly electric species, the catfish’s discharge sits well above the faint signals used by weakly electric fish. Discharge pulses among strongly electric fish typically range from 10-150 volts, although some fish and eels are significantly stronger. Electric catfish are also opportunistic hunters of weaker electric species. The electric catfish preys specifically on smaller and weaker electric fish species, turning off its own electrical field to keep its presence unknown to prey, then suddenly releasing a large killing discharge once a target comes close. Anyone curious about how this species compares to its non-electric relatives can browse the broader catfish species guide for context.
4. Stargazer
Stargazers are one of the stranger entries on this list because they break the usual electric fish rulebook. Most electric fish are also electroreceptive, meaning they can sense electric fields, but the stargazer family, Uranoscopidae, is the only exception. In other words, stargazers can zap but cannot “feel” electricity the way an electric eel or knifefish can.
These flat-bodied ambush predators live buried in sand along ocean floors, with only their upturned eyes exposed. Stargazers bury themselves in the sand to ambush passing prey. Their electric organ sits just behind the eyes, in the genus Astroscopus, which is one of the strongly electric fish found in the oceans, alongside certain skates and rays such as the torpedo ray.
Curiously, the stargazer’s shock is not primarily a hunting tool. Stargazers do not use the electrical organ behind their eyes to stun prey; their shock is around 50 volts, but it is primarily used for defending against predators, and it should deter most threats, though they have also been known to bite swimmers and divers that stray too close. That makes the stargazer more of a self-defense specialist than a stunning predator, closer in role to other ocean fish that rely on avoidance and camouflage rather than active hunting electricity, much like how open-water species such as tuna species rely on speed instead of any electrical defense at all.
Key Insight: The stargazer’s inability to sense electric fields shows that electrogenesis and electroreception, while usually paired in nature, are not automatically linked. A fish can generate a shock purely as a weapon without ever being able to detect one.
5. Knifefish (e.g., Amazon Knifefish)
Knifefish represent the weakly electric side of the spectrum, and South America’s Gymnotiformes are the largest group within it. The Gymnotiformes, or South American knifefishes, are one of the two major groups of weakly electric fish, alongside the African Mormyridae and Gymnarchus, and the two groups evolved convergently with similar behavior but different electroreceptors and electric organ placement.
Two well-studied examples illustrate the wave-type discharge typical of this group. The brown ghost knifefish, Apteronotus leptorhynchus, and the knifefish genus Eigenmannia both produce wavelike electric organ discharges that stay on almost continuously rather than firing in short bursts.
Ghost knifefish, a related group in the family Apteronotidae, have become popular in the aquarium hobby. Black ghost knifefish are popular aquarium fish due to their peaceful natures, and as weakly electric fish in the genus Apteronotus, they belong to the family Apteronotidae, characterized by long, slender bodies and long anal fins, with 96 recognized species in the family. They also swim in ways most fish cannot: these fish typically reach between 7-20 inches long depending on the species and are excellent swimmers, using their ribbon-like anal fins to undulate forward, backward, vertically, and to hover in place.
In the wild, ghost knifefish favor rough water rather than calm pools. Ghost knifefish are found in subtropical and tropical freshwater rivers in South America, preferring turbulent, fast-moving waters in complex habitats such as those found in the Amazon River. A closely related glass knifefish shows the same lifestyle in a different body shape: the Glass Knifefish, also known as the ghost knifefish, is commonly found in South America and can grow up to 20 inches long, with a flattened body and long tail that gives it a translucent, ghostly appearance. Its electrolocation works the same way as its relatives: it uses electrolocation to navigate and hunt in dark waters, emitting electric signals from an organ in its tail and sensing the environment through the electric fields created by objects around it.
Because several knifefish species are common in the home aquarium trade, hobbyists researching tank mates often cross paths with guides covering popular aquarium fish types, or community-tank staples like tetra fish varieties and angelfish species, since knifefish are generally kept alongside calmer, similarly peaceful tankmates.
6. Mormyrid (Elephantfish)
Mormyrids, commonly called elephantfish for their elongated, trunk-like snouts, form the other major branch of Africa’s weakly electric fish. The Mormyridae, or elephantfishes, belong to the order Osteoglossiformes and are one of the major groups of weakly electric fish. Unlike the continuous wave signal of a knifefish, mormyrids fire discrete pulses. In African mormyrids, pulse-EODs are constant all-or-nothing events, emitted in an irregular train of pulses depending on behavioral context.
Each mormyrid species tends to produce a distinctive, recognizable pulse shape, almost like a signature. That signature is not always perfectly stable, though. Researchers studying wild specimens of Brienomyrus niger found that certain mormyrid specimens very rarely showed electric organ discharge waveforms that appeared totally deviant compared with all other specimens ever seen before, possibly due to an ontogenetic anomaly or imperfect regeneration after a predator’s attack. In other words, an injury to the tail can scramble a fish’s electric “voice.”
Mormyrids rely on these pulses for more than just navigation. Weakly electric fish use their electric organ discharges for navigation, electrolocation with electroreceptors in their skin, and electrocommunication with other electric fish. That last function matters most in social species, where individuals appear to recognize relatives, rivals, and potential mates partly through pulse pattern alone. Aquarists who keep elephantfish alongside other African or community species sometimes reference broader stocking guides, including those covering oscar fish varieties and goldfish types, when planning tank compatibility, since mormyrids can be territorial toward similarly sized tankmates.
7. Gymnarchus
The last entry on this list is a genuine oddity: a single species that carries an entire family on its own. The aba aba, or African knifefish, is the sole species in the genus Gymnarchus and the family Gymnarchidae. Despite the common nickname “African knifefish,” it is not part of the South American Gymnotiformes group at all, it evolved its electric ability entirely separately.
Its scientific name, Gymnarchus niloticus, holds a special place in the history of electric fish research. Modern study of electroreception and electrogenesis effectively began with Hans Lissmann’s 1951 study of Gymnarchus niloticus. That early work laid the groundwork for nearly everything scientists now understand about how weakly electric fish sense their world.
Gymnarchus produces a continuous wave discharge rather than distinct pulses, placing it closer to knifefish than to its pulse-firing mormyrid neighbors, even though it lives in the same African rivers. Electric organ discharges need to vary with time for electrolocation, whether with pulses, as in the Mormyridae, or with waves, as in the Torpediniformes and Gymnarchus. This steady signal helps it hunt effectively in murky water, and it is not above targeting other electric species along the way. Its role among Africa’s smaller electric fish mirrors that of its South American strongly electric counterparts: electroreceptive predators of weakly electric fish are common in both South America, including the electric eel, and Africa, including several non-electrogenic catfish species, the mormyriform Gymnarchus niloticus, and the electric catfish.
Important Note: Voltage figures reported for electric fish species vary between sources depending on specimen size, water conductivity, and measurement method. The ranges cited throughout this article reflect commonly reported figures from the sources linked, rather than fixed values that apply to every individual fish.
To summarize how these seven species stack up against one another, the table below compares their discharge type, general power level, and primary use of electricity.
| Species | Electric Organ Discharge Type | Relative Power | Primary Use |
|---|---|---|---|
| Electric Eel | Pulse (dual weak/strong systems) | Very high (up to hundreds of volts) | Hunting and defense |
| Electric Ray (Torpedo Fish) | Wave | High (around 220 volts) | Stunning prey and defense |
| Electric Catfish | Pulse | High | Hunting and defense |
| Stargazer | Pulse | Moderate (around 50 volts) | Defense against predators |
| Knifefish | Wave | Very low (under 1 volt) | Navigation and communication |
| Mormyrid (Elephantfish) | Pulse | Very low (under 1 volt) | Navigation and communication |
| Gymnarchus | Wave | Very low (under 1 volt) | Navigation and electrolocation |
Taken together, these seven types of electric fish show that “electric” does not mean one single thing in biology. A stargazer’s defensive jolt, a mormyrid’s pulse-based social code, and an electric eel’s predatory volley all trace back to the same basic evolutionary trick, a repurposed sodium channel gene, deployed for entirely different jobs. Whether the goal is stunning a meal, warding off a predator, or simply finding a way through dark water, each species has turned the same raw biological material into its own specialized toolkit.