The sardine run

This amazing annual event on the marine wildlife calendar, dubbed ‘the greatest shoal on Earth’, usually starts between mid-May and early June, as mid-winter approaches in South Africa.

The sardines (Sardinops sagax) don’t always arrive on schedule, and sometimes they fail to arrive at all. Both 2006 and 2007 are examples of this, with no-shows by the little silver fish.

If and when they do run, the sardines swim close inshore to make use of the cold current that forms off Cape Agulhas (at the southern tip of Africa) and sweeps up the coast of KwaZulu-Natal.

Riding this current, they travel in huge silvery shoals many kilometres long and several kilometres wide. As they make their way north, there’s guaranteed to be an amazing show of predatory sea life, from birds to seals, sharks and dolphins, which turn out in great numbers for the feast.

According to A Guide to the Common Sea Fishes of Southern Africa (Struik, 1993), the sardines breed in the cold water off the Western Cape and Namibian coasts. The Natal Sharks Board and biologists at the University of KwaZulu-Natal say there is still a lot we do not know about the movement along the warmer east coast. Recent research, however, suggests that it is more of a range extension than a migration, as only about 2% of the total sardine population forms the big shoal, and does so only when a band of nutrient-rich water forms along the coast.