The Mystery of the Migrating Eel

Japanese eels spend their lives in rivers but travel thousands of miles to the deep ocean to spawn. After hatching, the tiny larvae drift back to freshwater, yet scientists still struggle to map their exact breeding grounds.

These remarkable fish are catadromous, meaning they perform a massive migration from freshwater streams to the open sea just to reproduce. Despite their status as a beloved culinary staple known as unagi, they are now critically endangered. Their complex life cycle makes them incredibly difficult to breed in captivity, leaving wild populations at the mercy of environmental changes. Their secret journey remains one of nature's most elusive puzzles.