The entire area surrounding a sardine shoal erupts with life. Some shoals have been estimated as being seven kilometres long, two kilometres wide and 10 metres deep and as they progress along the coast, usually quite close to the shore, the predators swirl around, through and over the shoals as they feed on the tens of millions of small silvery fish. Sharks and dolphins can be regularly seen as they power through the shoals, sometimes spinning metres into the air. Cape gannets, each with a wingspan of over a metre and a half wide, dive-bomb directly into the shoals, often plunging 10 metres below the surface to catch their prey. Watching these large birds plummet into the sea at high speed is a spectacular site in itself as gannet after gannet hit the water in a plume of spray.
Most of the action can be seen from tourist boats and sometimes even from the shore. Divers have the opportunity of seeing the frenzy from beneath the surface. Sharks and dolphins sometimes “herd” thousands of sardines into “bait balls and devour their hapless victims while the main shoals, adopting for a “safety in numbers” policy rush northwards along the coast.
The sardine run usually takes place sometime between mid June and early August as the movement of the fish is highly dependent on the presence of cold water, usually below 20 C which is only present during the southern hemisphere winter.
In their attempts to escape predators the fish sometimes strand themselves in shallow water