The Sardine Run is an annual phenomenon sparked by the entry of large shoals of sardines into the waters of southern KwaZulu-Natal during the winter months.
The KZN Sharks Board explains that although the great bulk of South Africa's sardine stock is to be found in the cooler Cape waters, each winter a small number of the shoal moves eastwards up the Wild Coast.
These shoals take advantage of cool water on the continental shelf of the east coast that occurs seasonally as a narrow band between the coast and the warm, southward flowing Agulhas Current.
KZN gear up for the annual sardine run as they are making their way to the warm waters of KZN. Sardines arrive in SA annually between May & July. We encourage visitors to start making early bookings for the chance to view this spectacular natural phenomenon. Video: @VisitSA_UK pic.twitter.com/zV7NJG6q3A
— Tourism KZN (@TourismKZN) May 14, 2019
It is not clear what advantage the sardines gain by entering KwaZulu-Natal waters.
On the contrary, in fact, local waters are less food-rich than are Cape waters, the favourable cooler conditions are only temporary and, to make matters worse for the sardines, they are accompanied by many predators which prey on them heavily.
Because the fish become concentrated near the surface in a narrow inshore band of water, the shoals are quickly located by schools of marauding predators that are whipped into a frenzy by this brief period of plenty in these otherwise less productive waters.
Sharks join gamefish such as shad, garrick and geelbek, and marine mammals like Cape fur seals and dolphins in hot pursuit of the shimmering mass of sardines, or each other.
As the shoals are driven to the surface, birds plummet out of the sky to pillage from above.
The appearance of common dolphins along the KwaZulu-Natal south coast is closely associated with the arrival of the Sardine Run and it has even been suggested that the female dolphins use the plentiful food supply to wean their calves and replenish their depleted fat stores.
The progress of the Sardine Run is closely monitored by anglers, who flock to the beaches and rocks to participate in excellent game-fishing.
Wind and current conditions may force the sardines very close to the beach, where they are easily caught using baskets, hand nets or even skirts! In fact, when sardines are beaching anything goes, and it is not uncommon to see grandmothers competing with teenagers for 'their' share of the feast in a social occasion that draws crowds into the surf and even larger crowds of awed and amused spectators.