Eel Fish: What Eels Are, Life Cycle, Eating and Dangers

An eel is a long, snake-shaped fish in the order Anguilliformes, a group Wikipedia puts at about 1,000 species in 20 families and 164 genera. True eels include freshwater eels, conger eels and moray eels.

The body plan is what gives them away. Wikipedia describes eels as having no pelvic fins, and many species have no pectoral fins either. The dorsal and anal fins run into the tail fin as one continuous ribbon along much of the body. The US Fish and Wildlife Service notes that the American eel is covered in a mucous layer that cuts friction and protects against pathogens, which is why a live eel is so hard to hold.

Sizes vary more than most people expect. The smallest, the one-jawed eel, is about 5 cm (2 in) long, while the slender giant moray reaches about 4 m (13 ft). The heaviest is the European conger at up to 3 m (10 ft) and 110 kg (240 lb) (Wikipedia).

An eel is a fish. It lives its whole life in water, and the US Fish and Wildlife Service classes the American eel as a fish that moves by undulating its long body. The snake connection is only in the look and in the name: Wikipedia notes that the Latin word for eel is built on anguis, which means snake.

Two quick checks separate an eel from a snake in a photo. An eel has a fin ribbon running along its back and belly into the tail, and it has gill openings behind the head. A snake has neither.

Plenty of long fish carry the name eel without belonging to Anguilliformes. Wikipedia names electric eels, swamp eels and slime eels as examples.

• Electric eel: a South American knifefish in the order Gymnotiformes, not closely related to true eels (Wikipedia). See our electric eel page.
• Wolf eel: a wolffish with large pectoral fins behind the head, which true eels lack. See our wolf eel page.
• Moray eel: a true eel, with no pectoral or pelvic fins at all. See our moray eel page.

The fastest field test is the pectoral fin. A clear, paddle-like fin just behind the head points away from a true eel.

Freshwater eels change shape and name several times. Wikipedia lists the stages as:

• Leptocephalus: a flat, transparent larva that drifts in the ocean
• Glass eel: the see-through young eel arriving at the coast; the US Fish and Wildlife Service gives 2 to 3 inches for American glass eels
• Elver: a young eel moving upstream
• Yellow eel and silver eel: the growing adult, then the mature eel ready to return to sea

American eels migrate to breed in the Sargasso Sea, which the US Fish and Wildlife Service describes as a 2-million-square-mile area of the North Atlantic between the West Indies and the Azores. European eels spawn there too, and Wikipedia describes a drift of about 300 days before the larvae reach Europe.

They can live a long time. The US Fish and Wildlife Service gives five to more than 40 years for the American eel, depending on whether it lived in brackish or fresh water. Wikipedia gives 15 to 20 years for European eels in the wild, and records one captive European eel, the Brantevik Eel, at 155 years.

True eels do not produce electricity. The fish that does is the electric eel, which is a knifefish, not an eel (Wikipedia).

Wikipedia explains that its electric organs are built from electrocytes, cells modified from muscle. When the fish fires, sodium floods into these cells and briefly reverses their charge. Some 6,000 electrocytes are stacked in series in the main organ, with about 35 such stacks side by side, which is how the discharge adds up to at least 600 volts. One species, Electrophorus voltai, has been measured at 860 volts. Our electric eel page covers the three species and the risk to people.

Eel is a traditional food in several countries, but it comes with specific cautions. Wikipedia notes that freshwater eel (unagi) and conger eel (anago) are common in Japanese cooking, and that jellied eels are a traditional east London dish.

• Raw blood: Wikipedia states that eel blood is toxic to humans and other mammals, and that cooking and digestion destroy the toxic protein. Do not eat eel raw.
• Moray eels: Wikipedia reports that giant and yellow-edged morays can build up high levels of ciguatoxins, that 57 people in the Northern Mariana Islands were poisoned after eating part of one cooked yellow-edged moray, and that morays are not recommended for eating. Some morays also carry a toxin in their skin mucus.
• Venom: none of the sources we checked describes true eels as venomous. The documented hazards are bites, raw blood and ciguatera from some morays.

If anyone feels unwell after eating eel or any fish, get medical help. In the US, Poison Control is 1-800-222-1222 (poison.org). There is also a conservation reason to think before buying: the eels most often eaten are among the most threatened, as the next section explains.

Wikipedia lists the European eel as Critically Endangered and the American and Japanese eels as Endangered. For the European eel, Wikipedia reports that the number of young eels reaching Europe has fallen by around 90%, possibly 98%, since the 1970s, and that the species is listed in Appendix II of CITES, which controls international trade.

Demand is large. Wikipedia's European eel article says the United States imports 11 million pounds of eel a year for its sushi industry. Breeding them is still unsolved: Danish researchers at DTU Aqua first bred European eels in captivity in 2006, and by 2022 larvae survived up to about 140 days, but the full life cycle has not been completed in captivity (Wikipedia).

Photograph the whole fish side-on, then take close-ups of these points:

• Behind the head: a small pectoral fin (freshwater and conger eels), no pectoral fin (morays), or a large paddle fin (not a true eel, for example the wolf eel)
• Belly: true eels have no pelvic fins (Wikipedia)
• Back and tail: one continuous fin ribbon joining the tail suggests a true eel
• Colour and size: American eel females reach 4 ft and 9 lb, males only about 1.5 ft (USFWS)

FishLens can suggest a match from a photo. Check the result against these marks before you keep, cook or release the fish, and see our guide to identifying a fish from a photo.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices are given with the date we checked them (25 September 2026); they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.