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The Difference Between Electric Eels and True Eels

What’s long and slimy and not that closely related?

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Psst...do you know the difference between true eels and electric eels? © Gregory Piper / Coral Reef Image Bank

You may not think about eels very much. And that’s OK, we can’t blame you—they’re not exactly the more charismatic critters in the ocean. It’s hard to compete with a fluffy otter or majestic whale when you are literally the villain in a Disney movie—I’m looking at you Flotsam and Jetsam. But today, we’re here to give these fanged-toothed, long-bodied creatures the attention they deserve by debunking a common eel myth.

Believe it or not, all eels are not created equal. Not all animals we call “eels” are even technically eels. They may look similar, but electric eels and true eels are in completely different families.

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An American eel, which is a true eel. © Erickson Smith

So, what is a true eel?

A true eel is an elongated finned-fish belonging to the order Anguilliformes. There are more than 800 species of eel ranging in about 2 in (5 cm) to 13 ft (4 m) in length. The longest eel ever recorded was a slender giant moray eel captured in 1927—it measured 12.9 ft (3.9 m) long, or about the height of an elephant!

Although most eel species primarily live in salt water, some eels travel between salt and freshwater environments to breed. For example, the European eel travels over 3,000 mi (4,800 km) from rivers in Europe to the Sargasso Sea to mate. Afterwards, the adults die, while the young baby eels drift on Atlantic currents back to Europe—a journey that can take two to three years. Baby eels, called glass eels, are transparent and are sometimes harvested for food.

Eels have strong jaws and a series of small, sharp teeth (trust us, you do not want to be bitten by a big eel—check out this story of a run-in with a moray eel). Don’t worry, though, your odds of being attacked by an eel are low, they’re mostly nocturnal and prefer to stay hidden in the sand and rocks.

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Electric eel © Karl Roby / Flickr

Ok. Then what is an electric eel?

Despite its name, the electric eel is a knifefish, not an eel. It is a member of the order Gymnotiformes and is more related to carp and catfish. It got its name from its eel-shaped body, which can grow to 9 ft (2.75 m) long and weigh almost 50 lbs (22.7 kg). Unlike true eels, who mostly live in salt water, electric eels are found in fresh waters in South America. Electric eels are also air-breathers, meaning they need to surface about every ten minutes to breathe (as opposed to true eels, who can breathe underwater with gills).

What makes electric eels stand out is (no surprise) their…electricity. They have three electric organs that contain cells called electrocytes. When the electric eel senses prey or feels threatened by a predator, electrocytes create an electrical current that can release up to 600 volts (if you are unlucky enough to be shocked by 600 volts, it won’t kill you on its own, but it will hurt).

What do I do with all this eel knowledge? 

Impress your friends! If you run into an eel swimming in a place that is not a river in South America, you’ve probably run into a true eel. If you feel an electric shock, you’ve run into an electric eel!

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