Life cycle of the European Eel

Eels are a catadromous freshwater fish meaning they live in freshwater and spawn the sea. Spawning takes place in the Sargasso Sea, but the exact location has never been found.

Eel arrive en masse somewhere under the dense sargassum weed that floats above them and after this 4000-mile migration from Europe they spawn and die. Fertile eggs float on oceanic current before eventually becoming leptocephali. These transparent willow shaped larva continue using currents on a long journey back to Europe. This can take up to two years and over this period a transformation takes place to the body of the young eel.

The willow shape flattens dorsally, creating a cylindrical body that is known as the glass eel stage. Upon arriving at the coastline, the glass eels use tides to carry themselves upstream. Upon entering fresh/brackish waters the glass eels start to pigment and become elvers. At around 8cm these young eels migrate upstream looking for habitat to grow and thrive in.

The freshwater stage of the eel, known as the yellow eel, is the longest period of an eel’s life and ranges from 5-20 years dependent on sex, resources and temperature. Upon reaching adequate size and adequate fat stores the yellow eel transforms once again for the final stage of its life.

This final stage is known as the silver eel. This impressive metamorphosis sees the animal change colour, pectoral fins widen, digestive tract shut down, eyes grow up to 10 times their original size and muscle mass increase. All these changes aid the eel on its journey back to the Sargasso Sea to start the cycle again.