European eel - Anguilla anguilla is a snakelike fish. They spawn in the Sargasso Sea and the larvae (Leptocephalus) migrate towards Europa in a three years migration. They enter freshwater, where they spent their lives. In the USA the American Eel Anguilla rostrata reaches the rivers in one to two years.
The life history of the eels is one of the most fascinating stories in oceanography, still enigmatic: Eel story