The Sardine Run, dubbed the "Greatest Shoal on Earth", is a fascinating natural phenomenon that occurs each year from May through to July. A cold northerly ocean current causes millions of sardines to gather in shoals and migrate north. Travelling a distance of over 1,000km along the rugged coastline from the Agulhas Bank towards Mozambique, the shoals form a swarming mass measuring up to 15km long, 3,5km wide, and 30m deep – a phenomenon visible by satellite. As the sardine run occurs so close to the shore, it is an event that everyone can experience – be it beneath or above the waves.
It remains an inexplicable phenomenon as to why the fish leave their nutrient-rich feeding and main spawning grounds of the Southern Cape coast for the emptier, sub-tropical Indian Ocean waters. To make matters worse, because of their appetite for plankton and the cold currents along the northern Eastern Cape and southern KwaZulu-Natal coastlines, the silvery swarm converges close to the shoreline and to the surface, making an ideal target for hungry predators higher up the food chain.
Once the shoals are located by predators both beneath and above the water’s surface, a feeding frenzy ensues, spawning one of the greatest wildlife events on earth. Snorkellers and scuba divers can witness one of the most fascinating hunting games where as many as 23,000 bottlenose and common dolphins employ a “bait ballâ€ technique; expertly herding the sardines towards shallow waters where the little fish form massive, heaving balls measuring up to 20m in diameter. Tens of thousands of voracious Cape gannets can be seen plummeting like fighter planes from the sky, while super-pods of dolphins, seals, whales, sharks, and game fish pillage the swarm from below. Once the predators have gorged themselves on this rare feast, the sea becomes calm and seemingly lifeless once again.