Most eels prefer to dwell in shallow waters or hide at the bottom layer of the ocean, sometimes in holes. These holes are called eel pits. Only the Anguillidae family comes to fresh water to dwell there (not to breed). Some eels dwell in deep water (in case of family Synaphobranchidae, this comes to a depth of , or are active swimmers (the family Nemichthyidae - to the depth of ).
This classification follows FishBase in dividing the eels into fifteen families. Additional families that are included in other classifications (notably ITIS and Systema Naturae 2000) are noted below the family with which they are synomized in the FishBase system.
Freshwater eels (unagi) and marine eels (conger eel, anago) are commonly used in Japanese cuisine - foods such as Unadon and Unajuu are popular but expensive. Eels are also very popular as food in Chinese cuisine, particularly Cantonese and Shanghai cuisine. Eel prices in Hong Kong often reached ¥1000 per kilogram, and even exceeded ¥5000 per kilogram at one time. Eel is also popular in Korean cuisine and is seen as a source of "stamina" for men. The European eel and other freshwater eels are eaten in Europe, the United States, and other places around the world. A traditional East London food is jellied eels. The Basque delicacy angulas consists of deep-fried elver (young eels). New Zealand longfin eel is a traditional food for Maori in New Zealand. In Italian cuisine eels from the Comacchio area (a swampy zone along the Adriatic coast) are specially prized along with the freshwater ones of the Bolsena Lake. In northern Germany and in The Netherlands, smoked eel is prized as a delicacy.
Fishing for eels is best done at night with either a gaff or a strong line with a small and square bloody piece of red meat.
Elvers were once eaten by fishermen as a cheap dish, but environmental changes have led to increased rarity of the fish. They are now considered a delicacy and are priced at up to £700 per kg in the United Kingdom.
Young eels are known as elver(s).
An urban legend states that wallets made out of electric eels (which, despite their name, are not eels) can demagnetize credit cards. This was proven to be untrue in an episode of the MythBusters TV show. As pointed out in the Straight Dope, eel-skin wallets are made from hagfish which are unrelated to electric eels. Furthermore, it seems that magnetic clasps, not eel leather, are to blame for demagnetization.
Eel blood is toxic, but the toxic protein it contains is destroyed by cooking. The toxin derived from eel blood serum was used by Charles Robert Richet in his Nobel winning research which discovered anaphylaxis (by injecting it into dogs and observing the effect).
On January 31, 1930, the Danish research ship "The Dana" captured what researchers believed to be a six-feet long eel larva near South Africa's Cape of Good Hope. This would have meant there were very long eels in the sea, since the typical eel larva is three inches (76 mm) long, while the adults can grow from about to long. In 1970, Dr. David G. Smith of the University of Miami identified the larva found as that of the spiny eel, an eel-like fish whose larval length is equal to its adult length, while the larval length of the true eel is much shorter than its adult length.
One of the famous attractions of the Pacific island of Huahine (part of the Society Islands in French Polynesia), is the bridge that crosses over a stream with 3- to long eels. These eels are deemed sacred by the locals, by local mythology.