European eel
The European eel (Anguilla anguilla) is a notable species recognized for its remarkable migratory life cycle, characterized by a long journey across the Atlantic Ocean. Beginning as larvae in the warm waters of the Sargasso Sea, these eels undergo a transformation from tiny, leaf-like leptocephali to glass eels, before migrating to freshwater habitats such as rivers and lakes. They can live in freshwater for several years, where they are commonly referred to as yellow eels due to their distinct coloration. The adult eels, which average 18 to 26 inches in length, eventually return to the Sargasso Sea to spawn, completing a round trip of nearly 3,000 miles (4,800 kilometers) each way.
This species is nocturnal and feeds on a variety of prey, including small invertebrates and fish, adapting their diet based on their physical characteristics. The European eel has been valued as a food source across Europe, both in wild catches and aquaculture. Unfortunately, the species is critically endangered, facing threats from overfishing, climate change, and parasites, leading to a significant decline in population. Eels can live for decades, with lifespans ranging from 7 to 85 years, and average around 55 years in captivity. The complex life cycle and critical conservation status of the European eel make it a fascinating subject of study and concern.
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European eel
The European eel is one of the most common and familiar eels in the family of freshwater eels and among eels in general. Its life cycle begins with swimming across the Atlantic as a baby eel. It then lives in freshwater for several years and migrates across the Atlantic again to reproduce and die. This is nearly 3,000 miles (4,800 kilometers) each way.
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Genus: Anguilla
Species: Anguilla
The common European eel performs an amazing feat of migration among the members of the animal kingdom. If nothing interferes or disturbs the natural life cycle patterns, a European eel swims across nearly the entire Atlantic Ocean twice in its lifetime. This is a distance of 3,000 to 5,000 miles (4,800 to 8,000 kilometers) each way.
The life cycle begins when adult eels spawn, or lay and fertilize eggs, in the warm waters of the Sargasso Sea in the western Atlantic Ocean. It is unknown how many eggs a female lays. The adults die shortly after spawning, and the baby eels hatch a short time later. They are born as leptocephali, or leaf-like larvae. In this larval stage, each is only 1/4 of an inch (1/2 centimeter) long. The leptocephali begin drifting on the North Atlantic and Gulf Stream currents toward Europe. Their journey to the coast may last up to three years.
Before they reach the coast, they metamorphose, or change, into a more eel-like adult form called “glass eels” which are around 2 3/4 inches (seven centimeters) long. After this stage, they are called elvers and have dark skin. Their bodies shorten and become thin and round like worms or snakes. Some elvers remain in the river mouths where the water is brackish, or slightly salty. Others migrate upstream to lakes, rivers, and ponds to live on the muddy bottoms. These are sometimes called yellow eels because of their yellow bellies. Some have pointed snouts and eat small invertebrates, or creatures without backbones, such as worms, mollusks, shrimp, and aquatic insects. Others have broader snouts and eat crabs, crayfish, small fish, and frogs. Both groups of eels are nocturnal, which means they feed mainly at night.
This pattern of spawning in saltwater and living in freshwater is called catadromous, and the opposite pattern is called anadromous.
These eels are a popular food in Europe. They are wild-caught and raised on eel farms. Natural predators include birds and mammals.
Adult European eels average 18 to 26 inches (45 to 65 centimeters) long. In the fall, many 7- to 12-year-old eels begin the journey downstream to the ocean and may even slither across the damp ground at night to get there more quickly. Their skin takes in oxygen but prevents the loss of moisture. Because of this, they can survive out of water for long periods. They stop eating and survive on fat in their bodies during the trip. They arrive in the Sargasso Sea in spring and then spawn.
The European eel is critically endangered. Overfishing for human consumption, climate change, and parasite infections have contributed to the species' population decline. The life span of a European eel is between 7 and 85 years. In captivity, they live an average of 55 years.
Bibliography
"European Eel." National Geographic, www.nationalgeographic.com/animals/fish/facts/european-eel. Accessed 15 Apr. 2024.
"Status Assessment 2022 - European Eel." OSPAR Assessment, oap.ospar.org/en/versions/2226-en-1-0-0-european-eel. Accessed 15 Apr. 2024.