Annual Sardine Run

During spring and early summer the sardines spawn in the cool waters of the Agulhas Bank. Most of the fish stay in the cooler waters of the Atlantic Ocean and end up along the west coast of Africa. Thousands travel up the east coast of South Africa in search of warmer waters.

It is thought that the sardine run, containing millions of individual sardines, occurs when a current of cold water heads north from the Agulhas Bank up to Mozambique. There it leaves the coastline and goes out into the Indian Ocean.

In terms of biomass, researchers estimate the sardine run could rival East Africa’s great wildebeest migration. However, little is known of the phenomenon. It is believed that the water temperature has to drop below 21°C in order for the migration to take place.

The shoals are often more than 7 km long, 1.5 km wide and 30 meters deep and are clearly visible from spotter planes or from the surface.

Sardines group together when they are threatened. This instinctual behavior is a defense mechanism as individuals are more likely to be eaten than large groups. This creates large bait balls, which can be 10-20 meters in diameter and extend to a depth of 10 meters. The bait balls are short lived and seldom last longer than 10 minutes.

It is thought that dolphins (estimated up to 18,000 in number) are largely responsible for rounding up the sardines into bait balls. Mostly the common dolphin but also the bottlenose dolphin. Once the sardines are rounded up, sharks (primarily the Bronze Whaler, but also Dusky Shark, Blacktip Shark, Spinner Shark and Zambezi Shark), game fish (like shad or elf, king mackerel, various kingfish species, garrick, geelbek and eastern little tuna) and birds (like the Cape gannet, cormorants, terns and gulls) take advantage of the opportunity.

The Cape Fur Seal follows the shoals up the Eastern Cape coastline as far as Port St Johns.

Some Sardine Facts:

  • Sardines live short lives, and grow quite quickly. They can reach a length of about 23cm in two years.
  • Sardines are filter feeders, sieving plankton from the water as it passes between their gills.
  • Sardines mature at about 19cm and reproduce during a prolonged breeding season from September to February.
  • Most breeding takes place on the Agulhas Bank in the Southern Cape, but some sardines do breed in KwaZulu-Natal.
  • KwaZulu-Natal waters are not particularly rich in plankton to provide a sufficient food source for the sardines.
  • Sardines, also recognized in South Africa as pilchards, occur in numerous cold water areas of the world.
  • Only a small percentage of the sardine schools go through KwaZulu-Natal waters, where about 700 tons are caught annually, while 4000 tons are caught in the Eastern Cape.
  • All the cans of pilchards in tomato sauce originate from the Cape. Some sardines are processed into fish meal.
  • The majority of South Africa’s sardines occur off the Western and Southern Cape, where about 100 000 tons are caught annually by purse seine vessels operating from harbours.
  • Cape gannets move up from their huge colonies in the Cape, the closest being at Bird Island, Algoa Bay.
  • Gannets operate in huge flocks, plunging out of the sky into the sardine shoals.
  • After gorging themselves, the gannets float overnight on the water in huge “rafts”.
  • Sardines are prey to a wide assortment of game fish such as geelbek, garrick and shad.
  • An adult dusky shark was found with 621 sardines in its stomach.
  • About 20 000 common dolphins pursue the sardine run up the coast from the Eastern Cape.
  • Cape fur seals and penguins also feed on sardines but are not often seen in KwaZulu-Natal waters.

Last Updated (Wednesday, 09 April 2008 12:32)

 
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