While the Sardine Run is renowned for its vast shoals of sardines, another remarkable player often steals the show beneath the surface. Shimmering schools of silver-blue mackerel, accented with flashes of yellow, frequently accompany the migration along South Africa’s Wild Coast. Although they receive far less attention than sardines, these fast-moving fish create some of the most breathtaking underwater spectacles of the season.
Images supplied by Tomer Shor.
Mackerel often travel alongside sardines or form mixed schools that can stretch for kilometres beneath the ocean’s surface. When predators begin to gather and the conditions are right, these enormous schools compress into dense bait balls, much like sardines. From below, the sight is mesmerizing – a pulsating metallic sphere of hundreds of fish turning in perfect synchrony, each movement coordinated with incredible precision.
A mackerel bait ball off Port St. Johns attracts an extraordinary lineup of predators. Cape gannets plunge from the sky, Bryde’s whales surge through the water, and several species of sharks converge to take advantage of the feeding opportunity. Because mackerel are larger and contain more oil than sardines, they provide a richer energy source, often resulting in particularly intense feeding activity. Dusky sharks, copper sharks, blacktip sharks, and bull sharks are among the species commonly seen hunting these bait balls along South Africa’s coastline.
But perhaps the most skilled hunters are common dolphins. Unlike some predators that smash directly into the ball, dolphins employ a far more precise strategy when feeding on mackerel. Working in pods, they corral the fish and maintain the bait ball’s shape, then pick off fish from the outer ball, just a few at a time. This restraint prevents the bait ball from scattering too soon, giving the dolphins repeated opportunities to feed.
In the accompanying video, the dolphins can be seen skillfully removing individual mackerel from the outer edges of the bait ball while simultaneously blowing streams of bubbles to keep the fish tightly compressed. It is an extraordinary display of communication, teamwork, and one of nature’s most sophisticated hunting strategies.
The presence of large mackerel bait balls during the Sardine Run highlights the incredible diversity and complexity of South Africa’s pelagic ecosystem. Far from being merely supporting players, mackerel are a vital food source for apex predators and an essential link in the marine food web. For divers, photographers, and wildlife enthusiasts, witnessing a mackerel bait ball under attack can be every bit as thrilling – and often just as dramatic – as experiencing the iconic sardine bait balls that have made the Sardine Run world-famous.
