New Zealand longfin eel is a traditional food for Maori in New Zealand.
The toxin derived from eel blood serum was used by Charles Robert Richet in his Nobel winning research that discovered anaphylaxis (by injecting it into dogs and observing the effect).
Eels generally are found in marine environments or, as in the case of the freshwater eels (family Anguillidae), catadromous, spawning in marine environments and with the young eels traveling back into freshwater.
Eels, members of Anguilliformes, lack pelvic fins and the associated skeletal structures.
The life cycle of the eel was a mystery for a very long time, because larval eels look very different from adult eels, and were thought to be a separate species.
Japanese cuisine commonly uses both freshwater eels (unagi) and marine eels (conger eel, anago).
The European conger, Conger conger, is the largest of the eel family, reaching three meters in length, and perhaps weighing up to 110 kilograms.
The so-called "electric eel" of South America is not a true eel, but is more closely related to the carp.
The European eel and other freshwater eels are eaten in Europe, the United States, and other places around the world.
Ecologically, eels are important in food chains, acting as predators of fish and such invertebrates as crustaceans and mollusks, and being consumed in its various stages by fish, mammals, birds, and various invertebrates.
Some eels dwell in deep water (in case of family Synaphobranchidae, this comes to a depth of 4,000 m), or are active swimmers (the family Nemichthyidae—to the depth of 500 m).
Freshwater eels are a food fish, particularly popular in Asia and Europe, where their sweet, rich, firm meat is considered a delicacy (Herbst 2001).
Most eels prefer to dwell in shallow waters or hide at the bottom layer of the ocean, sometimes in holes.
Eels also are popular among marine aquarists in the United States, particularly the moray eel, which is commonly kept in tropical saltwater aquariums.