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Why are young freshwater eels called glass eels?
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eel
The American eel (Anguilla rostrata) is found in habitats along the coast of eastern North America.
Young freshwater eels are referred to as "glass eels" because of their physical appearance during their early developmental stage. At this point in their life cycle, these juvenile eels are entirely transparent, which gives them a glass-like quality.123
After hatching in the ocean as leaflike larvae known as leptocephali, these fish undergo a metamorphosis before reaching coastal waters. As they arrive in these shallow areas to begin their migration upstream into freshwater habitats, they retain this transparent, colorless body form. Once they begin to settle and grow, they eventually develop pigment and transition into the stage commonly known as elvers.421