Chasing the Greatest Shoal on Earth: The Sardine Run, Through My Eyes and the Science

Every winter, when the aloes start to bloom on the hills of the Wild Coast, Transkei, and the air carries the first bite of cold, I feel the shift. The grass is heavy with dew, the mornings thick with humidity, and the smell of incoming storms lingers. For me, this moment always signals one thing: the sardines are coming.

I’ve spent over 16 seasons chasing this phenomenon—launching our RIB through cold surf, scanning the horizon for birds, listening to fishermen’s reports, and feeling, deep in my bones, when it’s time to move. But every year, as I float offshore—wind in my face, wetsuit dripping—I find myself thinking not just about the chaos around me, but about the deeper story. The science. The why.

Here’s what I’ve learned from years at sea—and what the latest research reveals about South Africa’s sardine run, one of the most spectacular and mysterious migrations on Earth.

The Sardine Run: What We See

Between May and July, massive shoals of Sardinops sagax surge up the coast from the Agulhas Bank, hugging the shallows off the Eastern Cape and into KwaZulu-Natal. From the boat, the first sign is often aerial—Cape gannets spiraling overhead, scanning the water, before diving like missiles into the ocean. Then the surface erupts—common dolphins herding sardines into tight bait balls, sharks slashing through the chaos, and Bryde’s whales lunging from below.

To most people, it looks like wild, coordinated madness. But under the surface, the story is far more complex—and fragile.

The Sardine Run: What We Know

For decades, the big question was: why do sardines leave their productive, temperate home on the Agulhas Bank and head into warm, predator-rich waters?

Recent genomic research by Teske et al. (2021) changed everything. They confirmed that the sardines involved in the run aren't a unique subtropical population, but rather part of the cool-water Atlantic stock. These fish are adapted to colder temperatures—and that’s exactly what they’re following.

Sometimes, narrow tongues of cold upwelled water, created by wind and eddy activity, creep up along the Wild Coast. Sardines follow these ephemeral corridors northward. But when the cold water disappears—when the wind drops or the Agulhas Current pushes inshore—they become trapped in warm, low-nutrient waters full of predators. Scientists now describe the sardine run as an ecological trap: the sardines swim into what looks like opportunity, but it's a corridor into danger.

I’ve seen it firsthand. Some years the run lasts for weeks. Other years, we chase the dream and it never quite arrives. But since 2020, we’ve been lucky—the sardines have returned in abundance, and the spectacle has been breathtaking. All of it depends on what’s happening beneath the surface.

The Agulhas Current: The Ocean’s Powerline

The Agulhas Current is the strongest western boundary current in the Southern Hemisphere. It flows down the east coast of South Africa like a liquid freight train—warm, fast, and unrelenting. Along the Wild Coast, where the continental shelf is narrow and steep, this current sometimes causes upwellings: cold, nutrient-rich water rising from the deep.

It’s during these brief moments—when conditions align just right—that the sardines move.

According to Lutjeharms et al., the Agulhas Current can exceed 2 m/s, with eddies and meanders forming near Port Alfred and East London. These spin off temporary cold-water patches, often just 10–15 km wide. If the sardines find them, the run ignites.

This is why the sardine run is so unpredictable. Every morning at sea, we’re not just hoping—we’re reading the ocean. The wind. The swell. The temperature. It's a system in motion, and we’re trying to stay one step ahead of it.

Cape Gannets: Living Missiles

If there’s one creature that defines the sardine run for me, it’s the Cape gannet (Morus capensis). I’ve watched thousands drop from the sky, folding their wings at the last second and exploding into the water to snatch a sardine—then swimming after others through the chaos. Their energy is electric. Their timing, razor-sharp.

But few people know their full story.

According to Crawford et al., Cape gannet populations are in decline. Colonies like Bird Island and Lambert’s Bay have shrunk as their main prey—sardines and anchovies—shift away from traditional feeding grounds. Today, gannets must fly farther and forage harder. The sardine run offers them a critical, albeit temporary, feast. Without it, chick survival drops, breeding fails, and colonies weaken.

The gannets aren’t just a signal for where the bait balls are—they’re a sentinel species, revealing the health of the entire marine ecosystem.

Fragile Magic

Despite its power and scale, this entire phenomenon is incredibly fragile.

Climate change is warming the oceans. If the Agulhas Current intensifies—as projections suggest—it could disrupt upwelling, erase cold-water corridors, and make the east coast increasingly hostile for sardines. Teske et al. warn that by 2055, the sardine run may no longer occur at all.

When you spend your life at sea, this isn’t theory—it’s real. You feel it in the temperature. You notice when the birds don’t show up. You launch in hope, but come home thinking.

Final Thoughts

For me, the sardine run is never just about the spectacle. It’s about a connection to a living, shifting system—one that ties wind to water, seabirds to deep eddies, and all of us to something bigger.

This run is a story written in ocean currents, told by predators, and chased by those of us lucky enough to be there. Science can explain some of it. But to feel it? You’ve got to be out there. Wet, cold, scanning the horizon—waiting for the birds to show you the way.

References Teske et al. 2021 – Teske, P. R. et al. The sardine run in southeastern Africa is a mass migration into an ecological trap. Science Advances, 7:eabf4514. https://doi.org/10.1126/sciadv.abf4514

van der Lingen et al. 2010 – van der Lingen, C. D., Coetzee, J. C., & Hutchings, L. Overview of the KwaZulu-Natal sardine run. African Journal of Marine Science, 32(2), 271–277. https://doi.org/10.2989/1814232X.2010.501581

Beal & Elipot 2016 – Beal, L. M., & Elipot, S. The Agulhas Current System as a Key Driver of Climate and Marine Ecosystems. Journal of Geophysical Research: Oceans, 121(8), 5337–5356. https://doi.org/10.1002/2016JC011889

Crawford et al. 2007 – Crawford, R. J. M. et al. Collapse of South Africa’s Cape gannet population reflects distributional and demographic shifts in prey populations. African Journal of Marine Science, 29(3), 493–508. https://doi.org/10.2989/AJMS.2007.29.3.8.337