How Strong Is an Electric Eel Shock? Volts and Real Risks

How many volts can an electric eel produce?

For many years, books gave about 600–650 volts as the electric eel’s maximum. Then, in 2019, a study that split the electric eel into three species also measured the discharges of each one:

The 860-volt reading is the highest voltage known from any animal. These figures come from only a few fish, so larger individuals may produce more. Voltage rises with size, because a longer eel has more electrocytes, the battery-like cells explained in how do electric eels make electricity?, stacked in a row. In the same study, a young Vari’s electric eel just 20 cm (8 in) long produced 151 volts.

The researchers measured each fish for less than a minute on an insulating plastic sheet out of the water, which shows the full voltage the electric organs can generate. In water, some of that voltage is lost as current spreads out around the eel.

Volts, amps and why both matter

Voltage is the electrical “push”, and current, measured in amperes (amps), is how much electricity actually flows. A shock’s effect on the body depends mostly on the current that passes through it and for how long, which in turn depends on the voltage and on the resistance of skin, water and air.

An electric eel’s discharge is high voltage but brief. Each pulse lasts about 2 milliseconds, and the current in water peaks at roughly 1 ampere at around 500 volts. The eel fires these pulses in volleys of up to several hundred per second. A household outlet runs at a lower voltage, 120 volts in the US and 230 volts in Europe, but it can deliver a large current without stopping, which is why it can be more dangerous than a single eel pulse.

How electric eels deliver their shocks

Electric eels use strong shocks mainly to hunt fish and to defend themselves. The high-voltage pulses act directly on the nerves that control muscles. A full volley makes every muscle in a nearby fish contract at once, freezing it for a moment while the eel sucks it in. Two or three quick pulses, instead, make hidden prey twitch so the eel can locate it.

Fresh water carries electricity poorly, so most of the current from an eel spreads out and weakens with distance. To deliver more of it, an eel can curl its body around prey so that its head and tail, the two ends of its battery, sit on opposite sides of the victim.

The leaping attack

When an electric eel feels threatened by a large animal partly in the water, it can lunge upward, press its chin against the threat and discharge while rising out of the water. In 2016, biologist Kenneth Catania filmed this behavior in the laboratory. Out of the water, the current cannot leak away through the surroundings, so the higher the eel rises, the more of its power passes through the target.

In a follow-up experiment published in 2017, Catania let a small electric eel leap at his own arm and measured the current. It peaked at 40–50 milliamperes, far above the level that triggers pain, although the painful sensation stayed in the arm that was touched. Extending his measurements to bigger fish, he calculated that large adult eels could deliver considerably more. The study concluded that the leap’s main purpose is to drive off predators with brief, intense pain.

Humboldt’s battle with the horses

The leaping attack explained a famous story. In March 1800, the German explorer Alexander von Humboldt watched local fishers on the plains of Venezuela drive about 30 horses into a muddy pool full of electric eels. The eels, some up to about 1.5 m (5 ft) long, rose from the water and pressed against the horses while shocking them. Humboldt saw two horses stunned and drowned before the eels, exhausted, could be caught safely.

For two centuries many scientists doubted the account, because no one had seen electric eels behave this way again. Catania’s experiments showed that the behavior is real.

Can an electric eel kill a person?

It is possible but rare. A single shock from a large eel causes sharp pain, muscle spasms and sometimes temporary numbness or loss of control of a limb. The greatest danger is in the water: someone who is knocked over or briefly unable to move after repeated shocks could fall and drown. Reliable reports of deaths are scarce, and many old stories are hard to verify.

Electric eels are not aggressive and do not attack people unprovoked. Most shocks happen when someone touches, steps on, handles or corners an eel in shallow, muddy water where it cannot be seen. Fishers in South America treat them with great respect, and the Tupi name for the electric eel, puraké, means “the one that numbs”.

The safest approach is simple: never touch or provoke an electric eel, keep hands and feet away from murky water where they live, and watch them only from a distance or behind aquarium glass. If someone is shocked, move away from the eel and seek emergency medical help immediately: call 911 in the US, 112 in the EU or 999 in the UK.

How do eels compare with other electric animals?

Electric eels hold the voltage record because they live in fresh water, which resists electricity. Marine torpedo rays produce less voltage, but because salt water conducts well, they can deliver higher current.