Sardines (pilchards) migrate every winter from the cold Atlantic Ocean, up the east coast (Indian Ocean) and into the warmer water off KwaZulu-Natal. During the summer and early autumn, warm water from the Agulhas Current with its associated sub-tropical fauna is present on the Transkei / KwaZulu-Natal coastline. At this time the water temperature can reach 25 degrees centigrade, and is too warm for temperate species such as the sardine. Towards winter this warm water recedes offshore and northwards and is replaced by a narrow band of cooler water suitable for the sardines, anchovy and herring that then move into this area. Due to the concentration of the shoals, they are quickly located by predators.
Some fish are driven inshore and netted by fishermen, others are trapped in the breakers and washed onto the beach. The Natal Sardine Run is a fascinating event with sharks, whales, dolphins, game fish, sea birds and man coming to the feast. People wade into the water to collect fish in buckets and bags while copper sharks, bloated by overindulgence, beach themselves in the quest for more. The Natal Sharks Board works hard to lift their shark nets, deployed to protect bathers from shark attack, ahead of the shoals to prevent damage.
The bait ball is probably the most exciting aspect of the Natal Sardine Run as it concentrates the many aspects of this phenomenon into a small area. This phenomenon normally starts with the common dolphins working together to herd a pocket of sardines into a small, tightly packet shoal called a bait ball. These fish can be driven from deeper, cooler water beneath the thermocline to the warm surface water, not normally associated with sardines. A bait ball can materialize from nowhere and disperse as quickly and is, therefore, an elusive event to film.
The pilot shoals had moved northwards and I had been working in dirty water off Port Edward on the KwaZulu-Natal coast for three days in scattered pockets of sardines. They moved in long narrow lines directly into the current. This is where I was expecting the main shoals to pass. In spite of the lack of concentrated sardine shoals, my time had not been wasted. During the three days I had dived with common and bottlenose dolphins, manta rays, copper sharks and humpback whales.
The boat dropped me off in front of an approaching shoal, easily identified on the echo sounder and by the surface activity. I drifted in the powerful Agulhas Current with Steve, my support diver, at about 6 metres in a cocoon of brown / green murk. This is the plankton-rich water that brings the sardines so far from their normal feeding grounds. A few scattered sardines raced past as we waited expectantly. I saw a sudden flash of grey as a small group of bottlenose dolphins came into view at incredible speed. They circled me for a while as I spun furiously around trying to keep them in my camera’s frame. Probably bored by my clumsy antics, they left as quickly as they had arrived.
Steve punched my arm and pointed down. The unmistakable shape of a shark cruised past, hardly visible in the murky water. Within the next few minutes I had seen about 10 sharks. In desperation to get a better shot I swam towards one as it swam away. The shark unexpectedly turned around and shot straight into my camera like a missile, nearly knocking it from my grasp, before speeding off. At this stage I was relieved when Steve suggested that we surface. The myth that you don’t get dolphins and sharks in the same area at the same time had been erased from my mind forever.
Back in the safety of the boat we spotted birds diving about 2 kilometres away. As we sped to the spot, I was pleased to note that the water was becoming much cleaner. Common dolphins, fast and agile, raced our boat towards the action. We arrived at the diving birds to find a scene of apparent chaos. There were dolphins everywhere, apparently swimming around without purpose but I was sure there was a game plan somewhere. The visibility here was about 15 metres. We jumped into the water with my camera already rolling expecting an exciting dive. However, what I saw took me totally by surprise. There were so many sharks in the water that, for an instant, I mistook them for dolphins. They darted around obviously excited. Steve pointed upwards and I saw a dark shape that I, at first, mistook for a humpback whale. Then I realized that we were beneath an elusive bait ball.
While these days it is not uncommon to see baitball footage taken in KwaZulu-Natal on television, but this was in the early days before such footage was available, thereby making the experience all the more incredible.
It is difficult to describe the spectacle. There were about 30 copper and blacktip sharks
visible at any one time but, I am sure, many more in the area. I was like a child in a sweet shop: I did not know what to grab (on tape) first. Some sharks would race into the ball and the sardines would scatter, only to regroup seconds later. Dolphins
circled the ball creating a bubble curtain, thereby giving the illusion that a large group of scuba divers were swimming below. The water was alive with the sound of dolphin communication. Suddenly, as one, the dolphins would charge the ball with a speed that amazed me. While the sharks sometimes bumped into us, I believe by mistake, in their feeding frenzy, rather than by an act of aggression, the dolphins thankfully missed us due to their sophisticated acoustic navigation. Once, unbeknown to me, a large copper swam between my legs. I was jolted and looked around, thinking it was Steve. However, he was too busy with his own problems as he fended one shark off with his speargun while screaming at another speeding past, centimetres from his mask. Periodically the frenzied activity would suddenly cease for a few minutes and an eerie calm would settle around the ball. The dolphins would continue to circle and then charge again. There was no doubt that they were working together as a highly efficient team.
What amazed me was that I saw no aggression between the sharks and the dolphins. The ball seemed to stay with us, whichever way we swam, as if it was sticking to us for protection and sometimes enveloping us in a dark mantle, making us feel most uncomfortable. Fish scales and half dead fish, stunned by the dolphin's explosive entry, sunk slowly down to be taken by the awaiting sharks. Previously I was concerned that scuba bubbles would deter dolphins and copper sharks while filming but on this occasion they seemed oblivious to our presence.
The resulting footage was used in the BBC's "The Blue Planet" series.