Diving in South Africa/Sardine run
The sardine run occurs most years between May and July when billions of sardines (Southern African pilchard Sardinops sagax) spawn in the cool waters of the Agulhas Bank then and move along the southern coast of South Africa, eastward at first, then northward as they follow the coastline. This migration is followed by large numbers of predators, which provide the main attraction for divers.
The run, containing millions of individual sardines, occurs when a current of cold water heads north from the Agulhas Bank up to Mozambique where it then leaves the coastline and goes further east into the Indian Ocean.
The shoals may be more than 7 km long, 1.5 km wide and 30 meters deep and are clearly visible from spotter planes or from the surface.
Sardines group more closely together when they are threatened. This instinctual behaviour is a defense mechanism, as lone individuals are more likely to be eaten than large groups, but this behaviour also encourages large numbers of predators to follow the shoals.
Thousands of dolphins are largely responsible for rounding up the sardines into bait balls. These bait balls are densely packed masses of fish and can be 10–20 metres in diameter and extend to a depth of 10 metres and may last for up to about 10 minutes. Once the sardines are rounded up, sharks , game fish birds and the occasional whale take advantage of the opportunity. This is the most desirable time for a diver to join the action.
The Cape Fur Seal follows the shoals as far as Port St Johns.