True eels
European eel, Anguilla anguilla
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Suborders

Anguilloidei
Nemichthyoidei
Congroidei
Synaphobranchoidei

True eels are teleost fish. They have long and narrow bodies like snake. Adult eels can be as short as 10 cm or as long as 3 m. It depends on their species. The large eels can weigh up to 65 kg.

Eels have fewer fins than other fish. They do not have all the belly and chest fins. The back and anal fins are long and usually connected to the tail fin. The fins do not have spines.

The shoulder bones are separate from the skull. The scales have smooth edges or are absent.

Eels hatch from eggs. Baby (larval) eels are flat and transparent (clear). They are called leptocephalus (Greek for "thin head"). A young eel is called an elver. For a long time people did not know where eels came from, because baby eels look very different from adults. They thought the babies were a different species.

Most eels prefer to live in the shallowest parts of the ocean. They live at the bottom of the ocean, sometimes in holes. Eels in the Anguillidae family come to fresh water to live there. Eels in the Nemichthyidae family swim about 500 m below the ocean surface. Eels in the Synaphobranchidae family live as deep as 4000 m below the surface.

Hand netting (catching with nets) is the only legal way of catching eels in England. It has been done for thousands of years on the River Parrett and River Severn.

Most eels are predators. They hunt their prey.

Classification

True eels belong to the order (group) Anguilliformes (Latin for "eel-shaped").

This order has 4 suborders (smaller groups) called Anguilloidei, Nemichthyoidei, Congroidei, and Synaphobranchoidei.

The suborders are separated into 19 families. The families are divided into 110 genera. The genera are then divided into species.

There are 400 species of eels in all.

Description

Eels are elongated fish, ranging in length from 5 cm (2.0 in) in the one-jawed eel (Monognathus ahlstromi) to 4 m (13 ft) in the slender giant moray. Adults range in weight from 30 g (1.1 oz) to well over 25 kg (55 lb). They possess no pelvic fins, and many species also lack pectoral fins. The dorsal and anal fins are fused with the caudal fin, forming a single ribbon running along much of the length of the animal. Eels swim by generating body waves which travel the length of their bodies. They can swim backwards by reversing the direction of the wave.

Most eels live in the shallow waters of the ocean and burrow into sand, mud, or amongst rocks. A majority of eel species are nocturnal, thus are rarely seen. Sometimes, they are seen living together in holes, or "eel pits". Some species of eels also live in deeper water on the continental shelves and over the slopes deep as 4,000 m (13,000 ft). Only members of the Anguilla regularly inhabit fresh water, but they, too, return to the sea to breed.

The heaviest true eel is the European conger. The maximum size of this species has been reported as reaching a length of 3 m (10 ft) and a weight of 110 kg (240 lb). Other eels are longer, but do not weigh as much, such as the slender giant moray which reaches 4 m (13 ft).

Life cycle

Eels begin life as flat and transparent larvae, called leptocephali. Eel larvae drift in the surface waters of the sea, feeding on marine snow, small particles that float in the water. Eel larvae then metamorphose into glass eels and then become elvers before finally seeking out their juvenile and adult habitats. Freshwater elvers travel upstream and are forced to climb up obstructions, such as weirs, dam walls, and natural waterfalls.

Eel-life-circle1
Lifecycle of a typical (catadromous) eel

Lady Colin Campbell found, at Ballisodare, the eel fisheries were greatly improved by the hanging of loosely plaited grass ladders over barriers, enabling the elvers to ascend.

Commercial species

Freshwater eels (unagi) and marine eels (conger eel, anago) are commonly used in Japanese cuisine; foods such as unadon and unajū are popular, but expensive. Eels are also very popular in Chinese cuisine, and are prepared in many different ways. Hong Kong eel prices have often reached 1000 HKD (128.86 US Dollars) per kg, and once exceeded 5000 HKD per kg. The European eel and other freshwater eels are eaten in Europe, the United States, and other places. A traditional east London food is jellied eels, although the demand has significantly declined since World War II. The Northern Spanish delicacy angulas consists of elver (young eels) sautéed in olive oil with garlic; elvers usually reach prices of up to 1000 euro per kg. New Zealand longfin eel is a traditional Māori food in New Zealand. In Italian cuisine, eels from the Valli di Comacchio, a swampy zone along the Adriatic coast, are especially prized, along with freshwater eels of Bolsena Lake and pond eels from Cabras, Sardinia. In northern Germany, the Netherlands, the Czech Republic, Poland, Denmark, and Sweden, smoked eel is considered a delicacy.

Elvers, often fried, used to be a cheap dish in the United Kingdom; but, during the 1990s, their numbers collapsed across Europe. They are now not just a delicacy, but the UK's most expensive species.

Eels, particularly the moray eel, are popular among marine aquarists.

Eel blood is toxic to humans and other mammals, but both cooking and the digestive process destroy the toxic protein. The toxin derived from eel blood serum was used by Charles Robert Richet in his Nobel Prize-winning research which discovered anaphylaxis (by injecting it into dogs and observing the effect). The poison used by Richet was actually obtained from sea anemones.

Eelskin leather is highly prized. It is very smooth and exceptionally strong. However, it does not come from eels. It comes from the Pacific hagfish, a jawless fish which is also known as the slime eel.

In human culture

The large lake of Almere, which existed in the early Medieval Netherlands, got its names from the eels which lived in its water (the Dutch word for eel is aal or ael, so: "ael mere" = "eel lake"). The name is preserved in the new town of Almere in Flevoland, given in 1984 in memory of this body of water on whose site the town is located.

The daylight passage in the spring of Elvers upstream along the Thames was at one time called "eel fare". The word 'elver' is thought to be a corruption of "eel fare."

A famous attraction on the French Polynesian island of Huahine (part of the Society Islands) is the bridge across a stream hosting 3- to 6-ft-long eels, deemed sacred by local culture.

Eel fishing in Nazi-time Danzig plays an important role in Günter Grass' novel The Tin Drum. The cruelty of humans to eels is used as a metaphor for Nazi atrocities, and the sight of eels being killed by a fisherman triggers the madness of the protagonist's mother.

Sinister implications of eels fishing are also referenced in Jo Nesbø's The Cockroaches, second book of the Harry Hole detective series. The book's background includes a Norwegian village where eels in the nearby sea are rumored to feed on the corpses of drowned humans - making the eating of these eels verge on cannibalism.

Sustainable consumption

In 2010, Greenpeace International has added the European eel, Japanese eel, and American eel to its seafood red list. Japan consumes more than 70% of the global eel catch.


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