The sardine run along the coast of Southern Africa is one of the largest marine life migrations on earth. Masses of sardines travel northwards forming large shoals, resulting in a feeding frenzy for predators and a captivating show for diver. Here are a few facts about the sardine run in South Africa.
- Where and when?
Every year between May and August billions of sardines (spawned in the cool waters of the Agulhas Bank) travel north along the east coast of South Africa. They follow a cool current heading from Agulhas Bank to Mozambique.
- It’s huuuuge!
Researchers believe that the sardine run could easily rival the great wildebeest migration in East Africa in terms of biomass. Some shoals span 7km long with a width of around 1.5km and a depth of around 30 meters!
- More than just sardines
The mass migration of sardines attract a large diversity of marine predators. Common dolphins, Cape gannet, cape fur seals and Bryde’s whales can be seen along with Blacktip and Dusky sharks to name but a few.
- Travel buddies
Humpback whales traveling from Antarctica to Mozambique accompany the sardines on their run. Instead of joining in the run, the whales join the sardines on their way to their summer breeding grounds in the warmer waters of Mozambique.
- Why are the sardines running?
The honest answer here is: No-one knows. There are a number of hypotheses (some of them contradictory) that try to explain this phenomenon. While some researchers believe that a sub population of sardines might be participating in a reproductive migration others believe that it isn’t a migration at all and that the sardines are pulled northward by currents, winds and upwellings.
- They like it cold
Sardines prefer cooler water (between 14 and 20° C) and it is believed that the water temperature needs to drop below 21° C for the migration to take place. Water along the south eastern coast of South Africa drops down to these temperatures during the Country’s winter months. The warm Argulas current relaxes between May and August, enabling cooler water to move northward from Agulhas banks towards South Africa’s Wild Coast and KwaZulu Natal.
- Scuba diver run
There is an old joke saying: “If you want to experience the sardine run, you will be the one running”. As any diver knows there is never a guarantee to see a particular marine animal on a dive – you can schedule your dives to certain sites and certain times but seeing what you came to see is never a sure thing. It is the same for the sardine run. Dive centres in the area often work along with aviation companies, fishing boats and land based observation centres in order to track and find the shoals. Some days divers can spend upwards of 8 hours out on the water with the hopes of finding a bait ball of sardines.
- The time the sardines didn’t run
The amount of sardines taking part in the sardine run dwindled drastically around 2013 with sardines arriving later than usual. There were concerns that the annual run might be a thing of the past but still the sardines persisted and 2018 saw one of the best runs in years.
- Age old tradition
The earliest written recording of the sardine run in Durban is from 1853. The newspaper The Natal Mercury reported sightings of a large shoal of mackerel seen close to shore and noted that it has never been seen before. Luckily for divers they have decided to make the trip an annual one!
- The bait ball phenomenon
If you are really lucky you can witness a bait ball while on a dive with the sardines on the run. Sardines are extremely sensitive to even the slightest change in water pressure. This means when one fish in a shoal moves the rest react. Predators use this to their advantage to move some of the fish into concentrated balls. Dolphins sometimes blow bubbles towards the ball to concentrate the fish even more before launching an attack. Sharks and cape gannets join in the feast and the fish become lethargic as the oxygen in the surrounding water decreases, making them easy prey.
The sardine run is as unpredictable as its on land counterpart- the great wildebeest migration between Kenya and Tanzania. It is also arguably even more spectacular to witness, because – let’s be honest- everything is just that much more spectacular under water.
*A version of this article first appeared at www.scubadiverlife.com