Head to head
Eel vs Electric Eel
The electric eel has a misleading name. True eels are an order of fish that mostly live in the sea and breed there, while the electric eel is a freshwater knifefish from South America that just happens to have a long, eel-like body. The shared shape hides completely different animals.
| Eel | Electric Eel | |
|---|---|---|
| Is it an eel | Yes | No, a knifefish |
| Order | Anguilliformes | Gymnotiformes (near catfish) |
| Where it lives | Mostly marine; some in fresh water | Fresh water of northern South America |
| Electricity | None (a few distant relatives sense it weakly) | Up to about 860 volts |
| Breathing | Gills | Gulps air at the surface |
| Life cycle | Freshwater eels spawn once at sea, then die | Breeds in fresh water; male guards a nest |
| Larvae | Transparent, leaf-shaped, drifting | Ordinary larval fish |
| Body length | Up to about 1.5 m (some marine species longer) | Up to about 2.5 m |
Eel vs Electric Eel: common questions
Why is the electric eel called an eel if it is not one?
Because early European naturalists named it for its appearance. It has a long, cylindrical, tapering body with no obvious separate fins along most of its length, which looks eel-like, and it lives in water, so the name stuck long before anyone understood fish relationships. By the time it was clear that the animal is a knifefish related to catfish, and not a member of the true eel order at all, the common name was fixed in every language. The same thing happened with the electric catfish, the wolf eel, and the spiny eel, none of which are true eels.
How does an electric eel generate 800 volts?
About four fifths of its body is given over to three electric organs made of thousands of flat, disc-shaped cells called electrocytes, which are modified muscle cells that have lost the ability to contract. Each electrocyte produces only about 150 millivolts, like a tiny battery, but they are stacked in long columns and wired so that the nervous system can fire them all at once. Stacked in series the voltages add up, reaching around 600 to 860 volts in a big eel, and the columns in parallel supply the current. The eel fires rapid high-voltage volleys to stun prey or repel a threat, and separate low-voltage pulses for sensing its surroundings in murky water.
Can an electric eel kill a person?
Directly, it is rare but not impossible. A full discharge from a large electric eel is painful and can cause muscle spasms, and the real danger is that the shock makes a person lose muscle control and drown in shallow water, or that repeated shocks from a large eel cause heart rhythm problems in someone vulnerable. Documented human deaths attributed to electric eels are very few. Farm animals and people wading in eel country are occasionally shocked. A true eel, by contrast, poses no electrical risk at all, though the large morays among the marine eels can give a serious bite.