South Africa’s sardine run might just be the greatest wildlife spectacle you’ve never heard of. So large is this annual fishy movement that in biomass terms alone it has been estimated to rival the epic wildebeest migration across the East African plains. But, as it mostly occurs underwater, it only receives a fraction of the publicity.
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What is the sardine run?
South African sardines, also known as Pacific pilchards, are small, silver, torpedo-shaped members of the herring family, which reach up to 25cm long. As the southern winter approaches around June, huge shoals migrate between the coastal waters of Cape Town and Durban. This, of course, is only a part of the attraction – as waiting in the wings to cash in on this vast, moveable feast is a huge array of marine predators, including sharks, dolphins, birds and whales.
Where does the sardine run take place?
The sardines’ journey begins in the shallow, cool waters of the Agulhas Bank, just off South Africa’s southern tip. The fish congregate, possibly in their billions, to spawn in February and March, with the eggs and larvae then transported by currents to nursery grounds primarily located in the nutrient-rich waters along South Africa’s western coast. Here, they take two years to reach sexual maturity, while their parents undergo a migration in precisely the opposite direction. Following the cold, coastal currents, the mature sardines will initially move eastwards, before heading up South Africa’s eastern shoreline.
Why do sardines migrate?
With no immediately obvious benefits, the exact reasons for the sardine mass migration are still not clearly understood, and for the sardines it appears little more than a one-way ticket. Preferring the colder waters found along the coast, the sardines are effectively penned in by warmer waters from the offshore Agulhas Current, which flows in the opposite (southerly) direction.
How big are the sardine mass migrations?
While the numbers of fish are simply impossible to estimate, in good years mega-shoals can be more than 7km long, 1.5km wide and 30m deep.
What are the predators of the sardine run?
In the early stages of migration, a few attendant Cape gannets appear to be the first sign the predators are closing in, but the game-changer is when the common dolphins arrive, any time between late May and early July. The only weapon the sardines possess is to dazzle the predators by well-coordinated and constant changes of direction. When all the sardines align their bodies with their immediate neighbours, the dense shoals alternate between light and dark with each synchronised twist and turn.
The dolphins counter this behaviour by rounding up pockets of sardines with streams of bubbles, before forcing them closer to the surface to form ‘baitballs’. With the dolphins trapping the sardines between the surface and the deep, blue sea, other predators then start piling in, with up to 18,000 common dolphins and thousands of copper sharks and Cape fur seals recorded in some years.
The sardines are not safe from above, either, as tens of thousands of Cape gannets plunge into the baitball from heights of up to 20m. During this period of no more than 20 minutes, the surface of the water appears to bubble, as the spectacle turns into a feeding frenzy. The pièce de résistance comes when a Bryde’s whale lunges through the baitball with its mouth agape, gulping down water and possibly thousands of fish.
For any sardines who survive these onslaughts, the future appears no brighter. With Durban representing the end of the cold-water upwelling, the fish then seem to vanish. While some researchers have suggested a few may return south via deeper and colder water, it’s believed most become trapped in subtropical and suboptimal temperatures and die.
The sardine run should never be taken for granted, as a whole food web depends on this seasonal bounty.
Where can you see the sardine run?
There are several places where you can witness the sardine across South Africa, including:
Coffee Bay, Eastern Cape
Located along the Wild Coast, boats looking for the sardine run launch from the mouth of the nearby Mdumbi River.
Gqeberha (formerly Port Elizabeth), Eastern Cape
This port city often represents the starting point for the sardine run.
Port St Johns, Eastern Cape
The coastal waters off this town are considered one of the places to catch the sardine run at its busiest and most frenetic, with late June and early July considered the best time.
Mbotyi, Eastern Cape
This is one of the most northerly spots to catch the sardine run before it breaks up. Boats launch from the Mbotyi River Beach in June and July.
East London, Eastern Cape
A busy and thriving port that also allows access to the run in its earlier stages, with early June thought to be best.
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Top image: a copper shark swimming through a baitball of sardines off the coast of South Africa. Credit: Getty
