Sardine Run

The sardine run is the annual northward migration of billions of Southern African pilchards (Sardinops sagax) that spawn on the cool Agulhas Bank and, in the southern-hemisphere winter, ride a narrow band of cold (roughly 14–20 °C) coastal counter-current up the Eastern Cape and into KwaZulu-Natal, a movement made possible when the warm Agulhas Current slackens and Natal Pulses and break-away eddies open a cooler inshore corridor. Sardine shoals have been reported up to 15 km long, 4 km wide and 40 m deep, large enough to be visible from the air and from space. The run is most accessible off the Wild Coast around Port St Johns, Mboyti and Coffee Bay between roughly late May and July, where the continental shelf runs unusually close to shore. Rather than diving a reef, expeditions launch small rigid-inflatable boats through the surf and follow gannet activity, then drop snorkellers or (on a stationary, dolphin-herded bait ball) divers into the open ocean to watch up to thousands of long-beaked common dolphins, copper and dusky sharks, plunge-diving Cape gannets, Cape fur seals and the occasional Bryde's or humpback whale tear a bait ball apart in minutes. Conditions are demanding and unpredictable: open swell, surf launches, water from 14–22 °C, and visibility anywhere from 2 to 30 m. Some years the shoals run late, thin out, or stay too far offshore to reach, so no operator can guarantee a bait-ball encounter.

• The run is driven by billions of Southern African pilchards (Sardinops sagax) migrating north from their Agulhas Bank spawning grounds along the Eastern Cape and KwaZulu-Natal coast, typically from May through July; shoals have been recorded up to roughly 7 km long, 1.5 km wide and 30 m deep, with larger estimates of 15 km by 4 km reported and the migration visible from space.
• Up to an estimated 18,000 common dolphins, mostly the long-beaked common dolphin, herd sardines into tight bait balls that other predators exploit, with the Cape gannet (Morus capensis) being the predator species most closely associated with sardine presence and Bryde's whales lunging through the balls from below.
• Sardines migrate inside a narrow band of cool water (preferring roughly 14–20 °C and avoiding water above about 21 °C): in winter the warm Agulhas Current slackens and a cold counter-current, aided by Natal Pulses and break-away eddies, opens an inshore corridor up the Wild Coast that the shoals follow toward KwaZulu-Natal.