How strong can an electric eel's shock be? As of November 2026, sources give different top voltages for electric eels: 600, 650, 800 and 860 volts. Scientists measured a shock of 860 volts from one Volta's electric eel, the strongest discharge known from any living animal, and that is higher than the 650 volts that had been cited before. They also measured a shock of 480 volts from an Electrophorus electricus 760 millimeters long. In a 2019 study, shocks from E. varii eels ranged from 151 volts for a 200 mm eel to 572 volts for a 609 mm eel, and the bigger an electric eel is, the stronger its discharge. Most of the time, however, an electric eel makes only a weak charge, about 10 volts or less, to find its way and to find prey, and at rest it gives off very little electricity.

An electric eel makes electricity with special cells called electrocytes, and it has thousands of them, and the electrocytes work like a stack of batteries. In an electrocyte, a nerve signal opens channels so sodium ions flow in and potassium ions flow out, which changes the voltage across the cell membrane. At rest, the two ends of an electrocyte cancel each other out, but when the cell fires, the back membrane switches and the cell makes about 150 millivolts. Large electric eels stack thousands of electrocytes in series, so the small voltages add up to over 600 volts, and the stacks run along the rear 80 percent of the eel's body. An electric eel has three electric organs: the two larger organs, called the Main and Hunter's organs, make the strong shock, and the small Sachs organ makes the weak pulses.

In a burst of shocks, an electric eel can send out as many as 400 pulses a second, and the shock is high in voltage but low in current, about one amp. The shock works on the nerves of the eel's food, which makes the muscles tighten. Scientist Kenneth Catania found that two or three quick pulses make hidden prey twitch, and the eel senses the twitch. Catania tested the nerve idea with fish that had been treated with a drug called curare, which blocks nerves from reaching muscles, and these fish did not twitch when the eel sent out pulses. After the shock, the eel opens its mouth to make suction and takes in its food. Scientists are not sure why an electric eel is not hurt by its own shocks, and the ideas include its large size and a layer of fat around the electric organ.

Electric eels are the only electric fish in South America that use their electricity to hunt and to defend themselves. In experiments, electric eels used their high-voltage pulses to find and track moving objects, as well as to stun. To test how eels track prey, scientists put a small metal conductor on a spinning disk, and the eels followed it and struck at it while giving off high-voltage pulses. When an electric eel is cornered by a large object sticking out of the water, it can leap up and press its chin against it while giving off a series of shocks. When an eel leaps, its voltage and current rise as it goes higher, and the current goes from the eel's chin straight into the target, instead of spreading out through the water.

Electric eels hunt at night, and for a long time scientists thought electric eels hunted alone. Then, in a small lake in northern Brazil, they found more than 100 adult electric eels together, and the eels were seen herding small fish into a tight ball before smaller groups of up to 10 eels sent out shocks together. At dawn and dusk, one group hunt in Brazil lasted about an hour and included five to seven high-voltage bursts, and the hunting eels rested almost still in deeper water the rest of the day. As of November 2026, hunting in groups is rare among fishes, and only nine other fish species were known to do it in 2021. Researchers think group hunting may happen only in places with plenty of prey and enough shelter for many adult eels.

For about 250 years scientists counted only one kind of electric eel, and as of November 2026 they know of at least three species. The electric eel was first described by the scientist Carl Linnaeus in 1766. One of the new species is named Electrophorus varii for the late Smithsonian fish scientist Richard Vari, and another is named E. voltai for Alessandro Volta, and the three kinds look much alike, so a scientist used their DNA to tell them apart. E. electricus lives only on the Guiana Shield highlands, E. voltai mostly on the Brazilian Shield, and E. varii in the lowland Amazon basin. By DNA, the lowland species split from the other two about 7.1 million years ago, and the two highland species split about 3.6 million years ago, at about the time the Amazon River took its modern path across the continent.

Electric eels live in rivers and ponds in South America, and many live in quiet, slow-moving, muddy water in the Amazon and Orinoco river basins. An electric eel has gills like other fish, but it cannot live without air, and it gets about 80 percent of its oxygen by gulping air at the surface. The water where electric eels live can be muddy and low in oxygen, and an eel has to come to the surface for a breath at least every ten minutes. In the dry season the water in the rivers drops, and electric eels can be left in small pools. When the rainy season comes and the rivers swell, young electric eels spread out into new areas.

Words to know

• electrocytes: power cells
• shelter: hiding place
• conductor: metal object
• curare: nerve-blocking drug