American eel

What it is

The American eel is a slender, supple fish with a snake-like body covered in a mucus layer that makes it appear naked. Minute scales are embedded beneath the skin, arranged irregularly rather than in overlapping rows. A long dorsal fin runs along the back and meets a similar ventral fin, while pelvic fins are absent. Coloration varies from olive green or brown on top to light gray or white on the belly, depending on water clarity. Females are typically larger and lighter than males. The head is conical with small eyes, a terminal mouth, and well-separated gill openings.

Where it lives

This species inhabits accessible freshwater streams, lakes, estuaries, and coastal marine waters across a wide latitudinal range. Its natural distribution spans the western North Atlantic coastline from Venezuela to Greenland, including Iceland. Inland, it extends into the Great Lakes and the Mississippi River system as far north as Minnesota and Wisconsin. Nonindigenous occurrences have been recorded in places like Lake Mead and California bays, though these populations often do not survive long-term.

How it lives

Eels are bottom dwellers that hide in burrows, tubes, or vegetation during the day and hunt at night. They possess a keen sense of smell to locate prey, which includes crustaceans, insects, small fish, mollusks, and worms. Diet varies by size, with smaller eels eating insect larvae and larger ones consuming fish and crayfish. Feeding activity decreases in winter as they enter torpor under mud. They are highly mobile, capable of climbing over vertical barriers, and may migrate between fresh, salt, and brackish waters seasonally.

Breeding and life cycle

Reproduction occurs in the Sargasso Sea, where females release millions of buoyant eggs. The eggs hatch into transparent, leaf-shaped larvae called leptocephali, which drift westward on ocean currents for seven to twelve months. Upon reaching the continental shelf, they metamorphose into glass eels, then elvers as they gain pigment. These young eels enter freshwater systems, where they grow as yellow eels for ten to twenty-five years before transforming into silver eels for the return migration to spawn.

Fish and people

American eels have historically been an important food source for indigenous peoples and supported commercial fisheries. In the 1980s, they were a top species by value in Ontario, but catches have declined significantly due to overfishing and habitat barriers. The primary market for US landings is the European Union. Conservation efforts include improving dam passage and using LED lights to guide eels away from turbines. Sport fishing has been closed in some areas, and commercial quotas have been cancelled in parts of Canada.

Status and threats

The American eel faces very high risk of extinction in the wild. Hydroelectric dams block migration routes, causing local extirpation, while pollutants like heavy metals bioaccumulate in their fat tissues. Sensitivity to low dissolved oxygen below dams further threatens populations. Although the US Fish and Wildlife Service did not list it under the Endangered Species Act in 2007 and 2015, Canada considered it threatened. As of late 2025, the Canadian government chose not to list it under the Species at Risk Act, citing stable abundance over two decades.

Relatives and look-alikes

The American eel belongs to the genus Anguilla, which includes other eel species. It is distinguished by specific morphological traits such as vertebral count and fin origin distance. Other anguillid eels share similar life cycles but inhabit different regions. Predators include largemouth bass, striped bass, bald eagles, and rainbow snakes, which sometimes eat only eels.

Questions people ask about American eel

Good reading and sources

• Closing In on Where Eels Go to Connect (Published 2015)The New York Times, Article

• American eel on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data