Eel, snakelike fish of class Actinopterygii, order Anguilliformes (or Apodes). There are about 15 families, 130 genera and 730 species, including moray, conger, snake and snipe eels. Except for the freshwater family Anguillidae, they are marine, abounding in shallow waters of tropical and subtropical seas. Some inhabit deep seas. Ten families and over 35 species are reported in Canada. The American eel (Anguilla rostrata) occurs widely in eastern Canadian fresh waters.
Eels, typically, are elongated, round in cross-section at the front and laterally compressed toward the back. They lack pelvic fins; the dorsal and anal fins are usually continuous with the tail fin. Most species lack scales. Eels are predaceous and tend to be nocturnal.
The American and European eels are catadromous, that is, they spend their lives in fresh water, returning to the ocean (the Atlantic, near the West Indies) to spawn and die. Larvae take 1 year to reach the N American coast and probably 3 years to reach the European coast. Spawning behaviour and exact place and time of spawning are subjects of continuing research. These eels are highly regarded as food, especially when smoked.