Eels are small, ray-finned fishes best known for their elongated, worm-like bodies. They belong to the order Anguilliformes, which comprises approximately 800 species, 19 families, and 111 genera.
These enigmatic creatures, with their serpentine bodies and enigmatic life cycles, have captivated the human imagination for centuries with their diverse life stages and feeding habits. Their ability to thrive in both fresh and saltwater environments hints at a remarkable resilience.
They occupy a crucial niche in the food web as both predators and prey, contributing to the delicate balance of marine and freshwater environments. Unfortunately, however, Greenpeace International added them to its red list of seafood in 2010, with Japan consuming over 70% of the total number of eels captured globally.
Appearance
The eel’s wormlike bodies set them apart from the crowd. 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. They have sharp teeth. Their weight varies depending on these factors, ranging from one ounce (30 g) to over 55 pounds (25 kg).
These fishes’ body color range from black or drab grey to colorful and patterned. European conger is the heaviest eel species, reportedly weighing 110 kg and measuring up to 3 m (10 feet).
Another important feature is that they don’t possess pelvic and pectoral fins. Instead, each has a dorsal, anal, and caudal fin around the tail tip.
Their long, slender bodies allow them to navigate currents and crevices with ease. Their ability to breathe through their skin in addition to gills grants them remarkable adaptability.
Eel Species
Some of the more famous species of eel include:
- American Eel (Anguilla rostrata): Found along the Atlantic coast of North America, these eels undertake incredible migrations between freshwater rivers and the Sargasso Sea to spawn. They are a vital part of the food web in their ecosystems.
- European Eel (Anguilla anguilla): Similar to the American eel in life cycle and ecological role, the European eel inhabits rivers and coastal waters across Europe and parts of North Africa. They face conservation challenges due to habitat loss and overfishing.
- Snake Eels (Ophichthidae): These eels possess long, slender bodies and pointed snouts, resembling snakes. They burrow in sandy or muddy bottoms in shallow coastal waters, feeding on small invertebrates and fish.
- Garden Eels (Heterocongrinae): These fascinating eels live in colonies, protruding from sandy bottoms like a field of swaying stalks. They feed on plankton drifting in the currents.
Habitat
Eels spend most of their adulthood swimming in fresh and salty waters. They are also bottom dwellers who can hide in different shelters like snags, murky waters, tubes, and burrows.
Eels are found in streams, rivers, silt-bottom lakes, and others during their freshwater stage.
However, since they occasionally migrate between brackish, salt, and freshwater habitats, they can also be found in coastal wetlands, river systems, and oceanic waters.
A slightly more unusual migration pattern can be seen for the European eels. They are “born” in the Sargasso Sea in the Western Atlantic Ocean, but then migrate to the coasts and rivers of Europe and North Africa where they grow and mature for a period of several years to several decades, before migrating back to the Sargasso Sea to spawn and start a new generation.
Eels spend most of their adult life in freshwater but return to the ocean, where they are reproduced to spawn.
The Japanese eel, a highly sought-after traditional food in Japan, is widely distributed in East Asia and constitutes a significant portion of the country’s aquaculture production.
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.
Most eels are nocturnal, meaning they feed at night when they feel safest. During the day, they hide under logs, rocks, and mud.
Reproduction
Their life cycle consists of development and early growth in the open ocean with free-floating eggs and larval stages.
In this species, both sexes pass through successive phases of neutrality, precocious feminization, and juvenile hermaphroditism before becoming definitively male or female, the sex being determined mainly by environmental factors.
They begin their life as leptocephali, flat and transparent larvae. The larvae are plankton that spend 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 juvenile eels as they transition to fresh water, where they mature and spend most of their life as adult eels.
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.
5 Amazing Facts About Eels
- Eels’ lives begin as zooplankton, known as leptocephali, which then metamorphose into glass eels and turn into elvers before becoming adults.
- The elongated body of eel fishes, sometimes laterally compressed, is the main external feature that distinguishes eels from most other fishes.
- Many eel species feed under the cover of the dark at night and hide under logs, mud, and rocks during the day.
- 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.
- Eel species with high economic value, like the American, European, and Japanese, are endangered.
FAQs
Is eel a fish or a snake?
Eels have all the characteristics of fish, though both are in the phylum of chordates. According to scientists, eels are classified under the Anguilliformes, consisting of over 800 species, 19 families, and 111 genera. So, the external features of eels and snakes may be the same since they belong to the same phylum or have a common origin.
Can an eel bite you?
Yes, some eels can bite you and cause serious injuries. For example, the leaf-nosed moray eels’ bites are typically painful and can cause much bleeding. These fish can cause great harm because their teeth are adapted to hold their prey tight and prevent them from escaping. Besides, they have another set of jaws that can help them hold their prey. So, the impact of the bite can range from minor to severe.
Can you eat an eel?
Yes, you can eat eels without any problem. Despite their snake-like appearance, these animals are some of the safest to eat. That’s why they are popular in Korean cuisine. Men with stamina issues also cherish their medicinal value. Many people enjoy eating European eels in Europe, the US, and other places. Besides, jellied eels are some of the traditional east London foods, though their demand began to drop after World War II.
Can eels change their gender?
Yes, some eels can change their gender. For example, the blue ribbon eel can undergo an immense transformation during its lifetime and switch its gender to a different one. It can begin life as male but switch to female as it matures. While this is somewhat common in the fish world, it occurs in the eel world more frequently than you would naturally expect.
Are eels electric?
Yes, but only one species! The electric eel (Electrophorus electricus) is not a true eel but a type of knifefish. It possesses specialized organs that generate powerful electric shocks to stun prey and defend itself.
