We don't know how freshwater eels know exactly when to return to the ocean.

As a female eel,Elaine will be quite solitary for most of her life in the stream,eating whatever falls in the water:grasshoppers, crickets, small fish,insect larvae, frogs, baby birds,almost anything she can get her mouth around.And she will grow quite big,up to four feet long and weighing as much as thirteen pounds.We don't know exactly how fresh water eels know when it's time to return to the ocean,but something calls to them.And their fall migration is one of the largest unseen migrations on the planet.