Is Eel a fish?

In this post, we will answer the question “Is Eel a fish?”. We will also outline the Eel general biology and ecology.  

Is Eel a fish?

Yes, Eels may look like snakes, but they are fish. There are over 800 different species of eels.

The eels are part of a fish family that live in rivers and seas and are spread across temperate and tropical waters of the Indian, Pacific, and Atlantic.

In addition to their strange appearance, their origin is also jaw-dropping, these specimens are considered to be one of the oldest animals in the world. Such proof came from Eel fossils found dating back to 20 million years ago.

These animals are easily recognized in the water, mainly due to their body, which is elongated and can measure from 70 centimetres to two metres. These physical characteristics can vary according to your species. Females are usually largest in length than males.

Their heads are dotted and many have wide mouths with very sharp fang-like teeth. Their skin is covered with a kind of mucous secretion, which makes it easier for the fish to slide through structures and also to escape from its predators. Eels also have scales, but they are microscopic.

The body is usually coloured with a greenish-brown tone, tending to black. Their bellies vary between yellow and white. Two small fins are located on the back of their head.

Locomotion

Eels tend to undulate when they are moving and they use a fin on their back that is directly linked to the anal fin. Finally, these both fins turn into one and help with movement.

Reproduction 

To spawn their eggs, the eel travels up to four thousand kilometres. When they reach the laying site, usually a region of up to 15 degrees Celsius and 500 metres deep, they mate and, after copulating and laying the eggs, in the end, they die.

The eggs hatch a few weeks later and move according to the water current. But it is not an as easy process as you may think, the hatchlings can take up to 4 years to get to their new home.

At birth, they have a smooth and transparent appearance, but after a period of growth, they adopt a look very similar to miniature adult eels. Soon after the hatchlings reach adulthood, they are ready for mating.

Feeding

The Eels can have an omnivorous diet if in need. However, they are classified as carnivore fish. They feed on crustaceans, small fish, molluscs, insects, and worms.

Eels Evolution

The oldest fossils of Eels came from prehistoric periods and pass the 100-million-year mark. These relics were found in southern France and Lebanon, but their origin is linked to the Mediterranean Sea.

There are two groups of these fish that derive from an ancestral species called Anguilla ancestralis. One of these groups is composed of seventeen species from the Indian and Pacific oceans and the other group is composed of two species of Atlantic eels. The life cycle of these animals is the same: they are born in warmer waters.

The ancestors of today’s eels reached the coasts of North America and Europe and also arose to the eels that live on these two continents. The only difference between them is in their number of vertebrae (there are 115 for European eels, while North American eels have only 107).

Electric Eels: High Voltage

Some Eels can produce electricity because of special cells they contain in their muscles called electrocytes. These electrocytes are responsible for creating the animal’s electrical defence and hunting system. The electricity is generated by conversion.

All the energy not spent by the animal is transformed into electricity by electrocytic cells. This electricity discharge covers all the eel, and in addition to protection and helping to get food, the animal uses this electric field for locomotion.

A characteristic of the electric eel is its similarity to the batteries we know and use in day-to-day life. The body of the electric eel is a stack with two different poles separated. From the head to the middle of their body, the positive pole dominates and everything else is the negative pole.

When adult, the electric eels have approximately 160,000 electrolytes. These cells are all over their bodies, making the animals a real superconducting natural living battery.

All this electrical energy travels through their bodies and the most impressive thing is that electricity does not travel through water. Since, if that happened, there would be no other fish swimming in the same water as the electric eel.

The ability of Eels to shock

Electric eels are a type of fish that can produce electrical currents to shoot down their prey. Thus, these animals have modified muscle cells that produce a small voltage. 

Since each electric eel can have thousands of these cells, an adult electric eel can deliver a shock of 860 volts. However, researchers were able to observe that eels can herd and hunt in groups. This causes a discharge from a flock of electric eels to exceed 8000 volts, the equivalent of a stun gun.

Hunting groups can have up to 100 electric eels. They form a ring around the school of prey and lead them into shallower waters. Once the fish are trapped, a number between 2 and 10 of the electric fish go to the centre of the enclosure and simultaneously discharge their energy. This gigantic current causes several tetras (common prey of electric eels) to fly out of the water and fall immobilized. Thus, the hunt ends and the hunters feed on fish that are still immobile or downed in the water.

Can you eat an eel?

Recently, a message suggesting that some fish should not be eaten by humans won the internet. Among these animals was the group of eels, which were indicated to contain high levels of mercury in their body. 

According to the message, eels retain a lot of mercury because they have high levels of fat. However, the truth is that you can eat eels without any major problem. There is no scientific proof that eels have higher amounts of mercury in their bodies than other fish, such as sardines and tilapia. It can even be possible that an eel has a high content of mercury in its body, but it would happen only with animals inhabiting toxic environments.

Ways to eat Eels

Eels can be consumed in many different manners. As a very common recipe in Asia, the eel is a dish that has won the world over the years. A good example of preparing eel is grilling, with the fish fillets without bones. Furthermore, in this case, the eel needs to be buttered, in addition to receiving a dose of other spices. This style is called Unagi no Kabayaki. 

Another way to make this fish is to grill it in its entirety, without making any division cuts. Then, after it is ready, the cuts take place.

Eels Ecological Characteristics

The eel is an animal that is at critical risk of extinction, as overfishing has become increasingly common. Thus, eels suffer a lot from this problem in many parts of the world. Most of the deaths happen when the adult eel is in the reproduction stage when the animal migrates from one place to another. 

Concerning their eating habits, you can say that the eel is a living carnivore. The animal usually consumes fish and crustaceans. In reality, even due to its anatomy, the eel is very dangerous and can have a very strong attack ability. This fish likes to hunt in darker hours when the prey is more vulnerable due to poor visibility.

Conclusion 

In this post, we answered the question “Is Eel a fish?”. We also discussed the eel general biology and ecology. 

If you have any thoughts or doubts, feel free to drop us in a comment below!

Frequently Asked Questions (FAQs): Is Eel a fish?

Where does the eel live?

Many species of eels live in warm oceans. Moray eels and congers are two well-known types of marine eels. Freshwater eels live in rivers and lakes, large and small, on almost every continent. They also travel to saltwater to reproduce.

Are Eels harmful to humans?

Yes, eels can be harmful to humans. They are one of the most dangerous fish in the ocean. Although they feed mostly on fish and crustaceans, they can become very aggressive and attack humans if they feel threatened. When threatened, it produces an electrical discharge that can reach 500 volts, enough to kill a full-grown male. The shock is terrible, the muscles are contracting so intensely that it is impossible to control the movements.

How many types of eels are there?

There are about 800 known species of eels known to science.

What causes eel to shock?

Electric eels use electricity discharges as a hunting strategy. They immobilise their prey with electricity. However, when threatened, electric eels can also discharge electricity, avoiding predators. The reason why has modified cells capable of generating electricity, the electrocytes. 

What is the voltage of an electric fish?

One of the three species of electric eel emits discharges of up to around 600 volts. However, some researchers have recently discovered two new species of electric fish in the Amazon. One of them is capable of releasing discharges of up to 860 volts, the highest voltage ever recorded by an animal.

What is the electric eel scientific name?

Electrophorus is the genus of the freshwater fish known as electric eels.

Can you eat eels?

Eels are not a very common dish in the Occident, but they are quite popular in many Asian cultures for their health benefits. Their meat is rich in vitamins and can be prepared in many different ways.

References 

Tsukamoto, K., & Nakai, I. (1998). Do all freshwater eels migrate?. Nature, 396(6712), 635-636.

Durif, C., Elie, P., Gosset, C., Rives, J., & Travade, F. (2003). Behavioural study of downstream migrating eels by radiotelemetry at a small hydroelectric power plant. Biology, management, and protection of catadromous eels, 343.

Arai, T. (Ed.). (2016). Biology and ecology of anguillid eels. CRC Press.

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