- A-Z Animals
Eels are bony fish, easily recognizable because of their snake-like appearance. They can live in both salt water and fresh water, and certain species migrate between the two, though the first and final stages of their lives take place in the sea. Some fish like the electric eel and deep-sea spiny eels are often mistaken for eels, which are not true eels though. Eeels are also well known for having one of the most unique reproductive cycles amongst all sea life.
Over 800 species of true eels are distributed worldwide, divided into 19 families and about 111 genera.
Some common freshwater eels: American Eel, European Eel, Japanese Eel
Some common saltwater eels: Conger Eels, Moray Eels
Size: They are elongated, ranging from 2 in (5 cm) in length for the one-jawed eel to 157.5 inch (400 cm) for the Slender Giant Moray eel.
One of the longest eel -the American eel- is about 19.7 inches (50 cm), while they are recorded to grow up to 59.8 inches (152 cm)
Weight: An adult eel is between 1 oz (30 g) and 55 lb (25 kg) on average though some can weigh much more. The European conger is the world’s heaviest eel, weighing 240 lb (110 kg).
Color: They appear in a wide variety of colors. Some are monochrome, while others are a mixture of different hues with various patterns like spots and stripes. For instance, the snowflake eel has a white or cream body with black blotches. On the other hand, the zebra moray appears deep brown with yellow or white stripes like the zebra.
Fins: Eels do not possess pelvic fins, while in some species the pectoral fins remain absent too. Their dorsal, anal and caudal fin fuse together to form a thin ribbon around most of its body.
These species can be found in oceans and seas worldwide.
Most eels live in shallow water, though a few can be found in deeper waters, almost up to 13000 ft (4000 m). They may in freshwater habitats like lakes, rivers, and ponds in the beginning, eventually migrating to saltwater locations like seas and oceans when ready to reproduce. However, some, like most Moray eels, live in saltwater throughout their life.
On average, their lifespan ranges from 15 to 30 years, though some can live for almost 85 years. The longest living eel, the Brantevik Eel, a European Eel species, survived up to 155 years in captivity.
They include small fish, crabs, shrimps, sea urchins, and even other eels. Those living in freshwater even eat larvae of worms and mosquitos.
The reproduction of the eel has remained an enigma, with details about their breeding staying unknown to this day. What scientists have uncovered so far indicates that they mate at the last phase of their lives by forgoing eating altogether and perhaps developing reproductive organs during this period.
Eels worldwide appear to have specific breeding sites, those from both America and Europe migrating to the Sargasso Sea, Japanese eels to the Suruga seamount, South African eels towards the north of Madagascar in the depths of the Indian Ocean, and New Zealand longfin eels near the nation of Tonga. All of them reproduce, give birth, and finally die.
They have a unique life cycle, going through four distinct stages, from an embryo to an adult. The larval stage of the eel, known as leptocephali, is transparent and flat. They drift about in the sea, eating marine snow for nourishment until they mature into glass eels. This stage travels from saltwater to freshwater, though some remain in the ocean for their entire lives. They then reach their 3rd stage, the elver as young eels are called, and begin moving further upstream. After becoming fully mature, they stay in their freshwater habitats until they return to the seas to breed.
Due to being a high-demand delicacy in Europe and Asia, the population has fallen drastically since the 19th century. The Japanese consume over 70% of the global catches. This has led to conservation efforts to prevent their numbers from declining further. Greenpeace International added the American eel, the European eel, and the Japanese eel to its red list of seafood species in 2010.
Scientists have been confused about the origin of the eel for a long time. Danish biologist Johannes Schmidt sailed the Atlantic ocean for 18 years trying to find the eel’s spawning grounds. After discovering some larvae, he speculated that they come from the Sargasso Sea
Some eels are considered threatening to humans, Moray eels being one of them, that attack if disturbed. Their bite could result in severe bleeding and can even cause human flesh to come out.
Despite the common misconception, electric eels are not real eels. They are closer to catfish. True eels are not known to generate electricity, though they may sense electric fields to navigate.
As mentioned previously, they have a single long backbone. Other than that, there are no major bones present in its body.
Eels look similar to snakes due to their long, narrow body stature.
No, all eels are fish and cannot survive out of the water, unlike most reptiles.
They are called leptocephali.
Most don’t, but some have scales embedded deep in their skin, giving them a slimy appearance.
Yes, they do, though scientists are yet to find the eggs of eels.
Larger fish, sharks, birds like herons and storks, and raccoons. Humans eat some species of the eel as well.
Yes, the blood of eels is toxic, discouraging predators.