Eel

Eels are special kinds of fish. They are long and slender and live in rivers, lakes, and oceans all over the world. They belong to a group called ray-finned fish and are part of the order Anguilliformes, which includes many different species.

Eels have interesting life cycles. They start as tiny larvae and grow into the adults we recognize as eels.

Many eels live in the sea, but some, like the genus Anguilla, spend most of their lives in freshwater. These fish are usually predators, meaning they hunt and eat other smaller creatures.

While most eels are true members of their fish family, some other eel-shaped fish, like electric eels, evolved their similar shape separately and are not closely related to true eels.

Description

Eels are long, thin fish that come in many sizes. Some are as small as 5 cm (2 in), like the one-jawed eel (Monognathus ahlstromi), while others grow up to 4 m (13 ft) long, like the slender giant moray. Most eels do not have pelvic or pectoral fins, and their dorsal, anal, and caudal fins join together to form a single ribbon along their bodies. They move by creating waves that travel along their bodies, and they can even swim backward by changing the direction of the wave.

Many eels are active at night and live in shallow ocean waters, often hiding in sand, mud, or rocks. Some eels live together in groups in special holes called "eel pits." A few types of eels live in deeper water, sometimes as deep as 4,000 m (13,000 ft). Only eels from the Anguilla group live in fresh water, but they return to the sea to lay eggs.

The heaviest true eel is the European conger, which can grow up to 3 m (10 ft) long and weigh as much as 110 kg (240 lb). Other eels, like the slender giant moray, can be longer but are not as heavy.

Life cycle

Eels begin as flat, clear baby fish called larvae. They float in the ocean and eat tiny bits of food. These baby eels change shape and become glass eels. Then they move to rivers and streams. They travel upstream, sometimes over small walls or waterfalls.

Most of these eels grow in freshwater, but some stay near the coast. When they are older, they return to the ocean to find a mate.

Classification

Different groups sort eels in many ways. For example, FishBase puts eels into 20 families. Other systems, like ITIS and Systema Naturae 2000, add more families.

Studies using genes show that a special group of eels came from deep-sea eels.

Taxonomy

The earliest fossils of eels are from the Late Cretaceous period in Lebanon. These early eels had simple features and are not closely related to modern eels. Modern eel fossils appear later, showing that eels were already diverse before a big event changed Earth long ago.

Eels belong to the order Anguilliformes. This group includes many families and types of eels, like moray eels and freshwater eels. Some fish that look like eels, such as the electric eel, are not true eels but belong to different groups.

Commercial species

Use by humans

See also: Eel as food

Eels are eaten in many parts of the world. In Japan, both freshwater eels called unagi and marine eels like the conger eel called anago are popular. Dishes such as unadon and unajū are tasty but can cost a lot. China also enjoys eels cooked in many ways. In India, especially in the Northeast, eels are a common meal. In Europe and the United States, freshwater eels are eaten too, though some kinds are in danger of disappearing.

In places like Hong Kong, eel can be very expensive, sometimes costing over 5000 HKD per kilogram! In Spain, young eels called elvers are cooked in olive oil with garlic and are a special treat. New Zealand has a long history of eating eels, especially among the Māori people. In countries such as Germany, the Netherlands, and Sweden, smoked eel is a favorite snack.

Eels are also popular with people who keep fish in tanks, especially types like the moray eel. It's important to know that eel blood can be harmful to humans, but cooking makes it safe. Because so many people enjoy eating eels, some eel species are now in trouble and need protection.

Sustainable consumption

In 2010, an environmental group called Greenpeace added the European eel, Japanese eel, and American eel to a list of seafood that should be used less to help protect these fish. Japan eats most of the eels caught around the world.

Etymology

The word "eel" in English comes from Old English ǣl. It is related to words in other languages. For example, in West Frisian it is iel, in Dutch it is aal, in German it is Aal, and in Icelandic it is áll.

The Latin word for eels is anguilla, and the Greek word is ἔγχελυς enkhelys. These words all share common roots meaning "snake."

The name Bellerophon might also be connected, meaning "the slayer of the serpent." This idea likely traveled to Greece from Anatolia. Because words for snakes and similar animals often have special rules in many languages, it is hard to know the exact original word for "eel."

Timeline of genera

Eels are fish that look like snakes. They belong to a group called Anguilliformes. This group has many types of eels, with about 1000 species. The word "eel" is also used for other fish that look similar, like electric eels, swamp eels, slime eels, and deep-sea spiny eels. These fish grow and change a lot from when they are tiny babies to when they become adults. They usually eat other animals.

In culture

The city of Ely in England is named after the eel. Long ago, people there caught eels from nearby waters.

In the early days of the Netherlands, there was a large lake called Almere full of eels. Its name means "eel lake." Today, a new city named Almere is where that lake once was.

In spring, young eels called elvers would travel up the Thames river.

On the island of Huahine in French Polynesia, there is a bridge over a stream with very large eels. These eels are important and sacred to the local people.

The book The Tin Drum by Günter Grass uses eels to show a difficult time in history.

The 2019 book The Gospel of the Eels looks at where eels come from and their place in culture.