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glass eel
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Illustration showing the metamorphosis of the American eel (Anguilla rostrata), with seven stages labeled A to G. The top three show increasingly larger transparent larvae, followed by three transitional forms, and ending with a more developed, elongated glass eel.
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glass eel

eel life cycle
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Illustration showing the metamorphosis of the American eel (Anguilla rostrata), with seven stages labeled A to G. The top three show increasingly larger transparent larvae, followed by three transitional forms, and ending with a more developed, elongated glass eel.
eel metamorphosis Metamorphosis of the American eel (Anguilla rostrata). (Aā€“C) Larvae, or leptocephali, of various sizes. (Dā€“F) Larvae in the process of metamorphosis. (G) The glass eel stage.

Glass eels are the transparent, juvenile stage of catadromous fish, most notably the eel of the genus Anguilla. These eels spend most of their lives in freshwater but migrate to the sea to breed.1

The life cycle begins when eels spawn in warm, saline waters like the Sargasso Sea. Their eggs hatch into transparent, leaf-like larvae called leptocephali. These larvae drift on ocean currents, such as the Gulf Stream, for about two and a half years. Upon reaching approximately eight centimeters, they undergo metamorphosis into elvers, then glass eels. These glass eels migrate to coastal areas and then swim upstream into freshwater streams, where they grow into yellow eels. After 10 to 15 years, they transform into silver eels, with enlarged eyes, and migrate back to the sea to spawn and die.1

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  2. migration - Catadromous fish

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