Popularly known as the “greatest shoal on Earth”, the KwaZulu-Natal sardine run involves tens to hundreds of millions of Pacific sardines packed into high density shoals to make the annual trip from the coast of South Africa to spend the winter in the Indian Ocean.

For sheer size and spectacle, this marine migration is no less impressive than the wildebeests on terra firma. But unlike the Serengeti herds, which migrate in search of food, the underlying reason for the sardine run is much less clear.