Anguillidae is a family of fishes that contains many of the freshwater eels. There are 16 to 20 species in this family, all in genus Anguilla. They are catadromous, meaning they spend their lives in freshwater rivers and return to the ocean to spawn. The young eel larvae, called leptocephali, consume plankton close to shore. They grow larger in size, and in their next growth stage are called glass eels. At this stage they live in tidal estuaries until they reach one year of age, at which they are known as elvers. Elvers travel upstream in freshwater rivers where they grow to adulthood. Some details of eel reproduction are as yet unknown, and the discovery of major eel spawning grounds in the Sargasso Sea is one of the more famous anecdotes in the history of Ichthyology. See Eel life history.
Freshwater eels are elongate with tubelike, snake-shaped bodies. They have large, pointed heads and their dorsal fins are usually continuous with their caudal fins and anal fins, to form a fringe lining the posterior end of the body. They have small pectoral fins to help them navigate along river bottoms. Their scales are thin and soft.
Anguillid eels are important food fish. Eel aquaculture is a fast-growing industry. Important food eel species include longfin eel, Australian long-finned eel, short-finned eel, and Japanese eel.