FWS Focus

Overview

Characteristics
Overview

The American eel is the only species of freshwater eel found in North America. It once made up over a quarter of the total fish found in many Atlantic coastal streams. Indeed, the eel is a valuable food source for larger fish and fish-eating birds, as well as people. Eels are catadromous, meaning they primarily live in rivers and estuaries, but migrate out to the ocean - the Sargasso Sea, to spawn. American eels are an elongated fish, with fairly small fins. They use their whole body to swim in undulating motions.

They are covered with a mucous layer, making them very slick. Scientists believe this mucous layer reduces friction as they swim in the ocean currents and protects them from pathogens that might enter the skin. 

Scientific Name

Anguilla rostrata
Common Name
American eel
FWS Category
Fishes
Kingdom

Location in Taxonomic Tree

Genus

Identification Numbers

TSN:

Characteristics

Characteristic category

Physical Characteristics

Characteristics
Color & Pattern

Female American eels are lighter in color, with smaller eyes and higher fins than males.

Size & Shape

Female American eels can grow up to 4 feet in length. Males only reach 1.5 feet in length.

Physical Characteristics

Eels are catadromous meaning they primarily live in rivers and estuaries but migrate out to the ocean - the Sargasso Sea, to spawn. After the young eel hatch in the Sargasso Sea they are carried on ocean currents for up to a year until they reach the coastlines of Greenland, Canada, the United States, and south to Venezuela. From there they swim upstream to their estuarine or freshwater destinations. In the United States, American eels migrate up the Atlantic and Gulf Coast rivers, including the Mississippi River and tributaries. They are also found inland in some lakes such as Lake Champlain and Lake Ontario. Others will remain in marine and brackish waters of coastal rivers and estuaries. The young eels will stay there until they reach maturity, then return to the Sargasso Sea to spawn and die. 

Weight

American eel can weigh up to nine pounds.

Characteristic category

Life Cycle

Characteristics
Reproduction

Each winter, mature American eels leave their riverine and estuarine environments to return to the Sargasso Sea to breed in the 2 million square miles of warm water located in the North Atlantic between the West Indies and the Azores. Millions of American eels gather here from across their range, and breed with others from any part of its range. This mating behavior perpetuates a single breeding population.  

Lifespan

Their lifespan varies from five to more than 40 years, depending on whether they lived or remained in brackish or freshwater environments during their life; eels mature and grow more quickly in estuarine waters than in freshwater. 

 

Lifecycle

During its lifetime, the American eel undergoes several metamorphoses from the fertilized egg stage, Leptochephali, to an adult. By the time they reach their coastal destinations, eels transparent larvae have developed into glass eels, and are about 2 to 3 inches long, with fins. They swim and feed at night on crustaceans, aquatic insects and small insects. During the day, they hide in burrows, tree snags, masses of plants and other types of shelters they can find close to shore.  

Characteristic category

Habitat

Characteristics
Habitat

During the day, eels hide among tree snags, plants and other types of shelters found close to shore. 

River or Stream
Characteristic category

Food

Characteristics
Food

Eels hunt at night, feeding on crustaceans, small insects, worms and other fish. 

Characteristic category

Behavior

Characteristics
Behavior

Eels are catadromous, meaning they primarily live in rivers and estuaries, but migrate out to the ocean - the Sargasso Sea, to spawn. After the young eel hatch in the Sargasso Sea they are carried on ocean currents for up to a year until they reach the coastlines of Greenland, Canada, the United States and south to Venezuela. From there, they swim upstream to their estuarine or freshwater destinations. In the United States, American eels migrate up the Atlantic and Gulf Coast rivers, including the Mississippi River and tributaries. They are also found inland in some lakes such as Lake Champlain and Lake Ontario. Others will remain in marine and brackish waters of coastal rivers and estuaries. The young eels will stay there until they reach maturity, then return to the Sargasso Sea to spawn and die. 

Geography

Characteristics
Range

American eels live in rivers and estuaries along the Atlantic coastline from Venezuela to Greenland and Iceland. They also are found along the Gulf Coast and Mississippi River. 

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