The sardine run happens in the winter months from May to August, when millions of sardines, Sardinops sagax, leave the southern Cape waters of the Agulhas bank, to follow the cold, nutrient-rich body of water up the African coast to Kwazulu Natal. This belt of cold water in which the sardines travel is formed by the winter storms of the Cape, pushing the cold water north, while the warm Agulhas current that runs from the north to the south traps this cold water against the coast.

Along the Transkei coast, the continental shelf pushes this cold water into its narrowest strip, concentrating the sardines and the predator load at its highest, creating  the conditions for some high-octane action. Film crews, amateur photographers, and ocean enthusiasts all flock to Port St. Johns, Mbotyi and the surrounding areas to get a space on the charter boats that provide the best opportunity for witnessing this event.

Port St. Johns is a small, rustic town on the Wild Coast, a 250-kilometre stretch of coastline which gained its name from its inaccessibility and treacherous shoreline. Although this makes for risky surf launches on the semi rigid inflatables, and hair-raising adventures at the crack of dawn with high-end camera equipment, it makes it all worthwhile when your skipper drops you right in the middle of a feeding frenzy. From the skies to the depths below, predators line up to feast on the protein-rich baitfish.

SCHOOLING TO SURVIVE
These bait balls form when common dolphins separate a small pocket of fish from the main shoal, and push it up to the surface. The dolphins circle the bait ball for a while, blowing bubbles from below, herding the little fish into a tight swirling mass. They then dart through together in a group to grab as many fish as they can. They will repeat this pattern over and over, until the last sardine is gone. These sardines know, if they lose the group, they are an easy target.

A large pod of bottlenose dolphins having fun in the large breaking waves, as they make their way northwards up the coast Image © Mark Van Coller

The sharks on the other hand, have no such skilled and organised feeding plan in place. Their strategy is to simply swim through the bait ball, mouth agape, consuming as many mouthfuls of fish as they can. That is why we, as divers, never hang around inside the bait ball! Sometimes that proves difficult, as the sardines often try to use divers as protection.

BATTERED FROM ABOVE
Once the bait ball is visible to the birds in the air, Cape gannets bombard it from every angle, raining down like bullets. When each gannet hits the water, it’s like an explosion below the surface, and one of my favourite moments of the sardine run. These gannets, with their wings folded back, tight as torpedoes, can easily dive to a depth of 15 metres to reach the bait ball, and sometimes grab up to three fish, before returning to the surface. Gannets have been recorded hitting the water at more than 85 kilometres an hour, which has often made me wonder: should I be diving with a helmet…?

For the rest of this article (Scuba Diver Issue 4/2015 OP No.4) and other stories, check out our past issues here or download digital copy here.

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