Eel

Eels are small, ray-finned fish best known for their elongated, worm-like bodies. They belong to the order Anguilliformes, which comprises approximately 800 species, 19 families, and 111 genera.

Some of the most common types of eels are the European eel, American eel, and Japanese eel. Greenpeace International added them to its red list of seafood in 2010. Remember, statistics show that Japan consumes over 70% of the total number of eels captured globally. The high demand is the reason we should adopt sustainable fishing methods.

Another important thing you shouldn’t forget to note is that many people use the term ‘eel’ for some eel-shaped fishes that aren’t true eels. In other words, before concluding that a fish referred to as an eel is a true eel, be sure it belongs to the order Anguilliformes.

Since eels are unique and play a critical role in the aquatic ecosystem, we’ve conducted in-depth research to help you understand them better. This article provides detailed information that suits experts and everyone interested in learning better ways to conserve the ocean ecosystem.

Appearance

Eels differ in size depending on their ages and species, ranging from two inches (5 cm) in the one-jawed eel to about 13 feet (4m) in species such as the slender giant moray. Their weight varies depending on these factors, ranging from one ounce (30 g) to over 55 pounds (25 kg).  

From research, we’ve discovered that the European conger is the heaviest eel species, reportedly weighing 110 kg and measuring up to 3 m (10 feet). These are great features. However, the eel’s wormlike bodies set them apart from the crowd.

Another important fact that can help you distinguish eel from other fish is that they don’t have pelvic and pectoral fins. Instead, each has a dorsal, anal, and caudal fin around the tail tip.

What about their body color? These fishes’ body color range from black or drab grey to colorful and patterned.

Diet

Eels are primarily carnivores, meaning most eat other animals. Studies show they depend on sea urchins, fish, shrimp, and other sea animals for food. Some of them eat the larvae of different insects and sea animals.

Some eel species are cannibalistic. They consume other animals of the same species.

Also, note that most eels are nocturnal, meaning they feed at night when they feel safest. During the day, they hide under logs, rocks, and mud.

Habitat

Eel spends most of their adulthood swimming in fresh and salty waters. As we’ve seen, they are also bottom dwellers that can hide in different types of shelters like snags, tubes, and burrows.

Importantly, you can find eels in streams, rivers, silt-bottom lakes, and others during their freshwater stage. However, since they occasionally migrate between brackish, salt, and freshwater habitats, you can also find them in coastal wetlands and oceanic waters.

Note that some eels are catadromous. What does that mean? Scientists use it to mean that eel fishes spend most of their adult life in freshwater but return to the ocean, where they are reproduced to spawn.

Reproduction

Much remains unknown about the reproduction of eels. However, they begin their life as leptocephali, flat and transparent larvae. The larvae are plankton that spends much of their time drifting along water currents and feeding on phytoplankton and other small particles and organisms.

After a while, the larvae metamorphose and turn into elvers or juvenile eels as they transition to fresh water, where they mature and spend most of their adult life.

Credit: Uwe Kils via Wikimedia Commons

Threats

Like other freshwater and marine animals, eels face overfishing, global warming, and pollution threats. Hydroelectric dams constructed in different parts of the world also threaten to wipe away their habitats and migration corridors.

However, since we have over 800 species of eel, we can’t make a general statement regarding their conservation status. A few of these fish are in high demand in our markets and are the most endangered. For example, the European eel is’ Critically Endangered’ due to parasites, overfishing, and other human activities.

The American eel is another good example. At one time, they were highly abundant in rivers and oceans. However, due to the construction of dams, the species is ‘Endangered’ as of now.

Facts About Eel

1. Eels’ lives begin as zooplankton, known as leptocephali, which then metamorphose into glass eels and turn into elvers before becoming adults.
2. The elongated body of eel fishes, sometimes laterally compressed, is the main external feature that distinguishes eels from most other fishes.
3. Many eel species feed under the cover of the dark at night and hide under logs, mud, and rocks during the day.
4. American eels typically live for five years but can reach between 15 and 20 years. Some reports indicate that a captive European eel can live for over 80 years.
5. Eel species with high economic value, like the American, European, and Japanese, are endangered.

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