European Eel Migration

A single, one-way spawning migration undertaken once in a European eel's life, in which adults leave the rivers, lakes and estuaries of Europe and North Africa where they have lived for up to twenty years and swim roughly 5,000 kilometers across the Atlantic to spawn and die in the Sargasso Sea. The resulting larvae then drift back across the ocean on currents over one to three years before metamorphosing into glass eels and entering European coastal waters and rivers, completing a life cycle that remained one of biology's enduring mysteries until the spawning grounds were finally located in the early twentieth century.