The Greatest Shoal on Earth as Sardine Migration Begins
Published: July 01, 2009
Billions of fish take part in thousand-mile journeyFrom Fred Bridgland in Johannesberg
They call it the Greatest Shoal on Earth, the ocean counterpart of the annual wildebeest migration across the Mara and Grumeti Rivers on Tanzania's Serengeti plains
Billions of sardines in shoals up to ten miles long, two miles wide and 130 feet deep are gathering this weekend off South Africa's Transkei coast to begin the great sardine migration a thousand miles eastwards towards Zululand and Mozambique.
Already predators have gathered and begun to feed on the swirling "sardine bait balls," herded to the surface by fast-moving, bubble-blowing dolphins. Within the next few days some 25,000 dolphins, thousands of ravenous sharks, great pods of killer whales and Bryde's whales, a profusion of marlin, tuna and other game fish, gangs of Cape fur seals and hundreds of thousands of Cape Gannets, storm petrels and albatrosses will follow the sardine run.
The run begins each year as cold winter water from the Antarctic sluices around Cape Point and Cape Agulhas and infiltrates the warm Indian Ocean seas off Zululand. The sardines, for reasons not fully understood, follow the cold water as it hugs tight to the coastline.
"I believe the sardine run is one of the greatest wildlife spectacles anywhere on earth," said Vic Peddemors, Professor of Marine Biology at the University of KwaZulu-Natal, who has extensively researched the run. "You are out there on a boat and the entire sea is just dolphins. You can see 2500 bottle-nosed dolphins swimming past. You might see up to 300 sharks on just one sardine bait ball 100 feet across."
John McIntyre, an underwater cameraman and scuba diver, who has positioned himself under the sardine shoals to film what he describes as "the marine equivalent of the Charge of the Light Brigade", said: "No camera can do it justice. I have witnessed dolphins fill the ocean as far as the horizon, humpback whales in all their majestic 40-tonnes glory, and, to cap it all, killer whales taking common dolphins as they devoured sardines."
Some 400,000 tourists, sports fishermen and extreme scuba divers have begun arriving in KwaZulu-Natal for the province's annual sardine festival, featuring concerts, gourmet feasts and wildlife and birding expeditions. The fish run so close inshore that they can be scooped up in buckets and hand-thrown nets. Women plunge into the surf and hoist out fish in billowing skirts, ignoring the sharks gorging on the sardines. The fish enrich the local mid-winter diet.
No one yet understands why the sardines suddenly migrate, pursued relentlessly by dolphins surfing through waves at 15 miles per hour. "It really is quite bizarre that there is this major biological event that we know so little about," said Peddemors, who is currently heading a shark research project for the New South Wales government in Australia. "It is not part of the breeding cycle."
Peddemors and other scientists are beginning to believe the sardine run is a vain attempt by the fish to extend their territory. They begin moving at some critical point during the short but sharp southern African winter as the cold water slick moves along the coast. But the sardine juggernaut always disappears mysteriously - to some unknown place deep in the ocean - when water temperatures begin heating up again in late July.