Crustacea Mass Migrations
Spectacular animal mass migrations are by no means limited to the vertebrates of the world. It is a universal phenomenon found in all major animal groups including birds, mammals, fish, reptiles, amphibians, insects and crustaceans. Although often small in body size, the epic journeys that many crustaceans undertake to feed or complete lifecycles are no less impressive. Well known examples are the daily movement of shoals of krill across the Southern Ocean, rising hundreds of metres to surface waters in the evening to feed and descending at daybreak to ocean depths to avoid predators.
The Sardine Run
Each winter the KZN South Coast is gripped by sardine fever. Huge shoals comprising millions of the silvery little fish enter KZN waters providing a feeding frenzy for predators and a spectacle not to be missed! Although the sardine Sardinops sagax also occurs in Australia, Japan, Chile, Peru and California, the grand scale of this annual sardine migration from the southern Cape waters to KZN appears to be unique.
The St Lucia Mullet Run
Historically, Lake St Lucia in northern KZN experienced a unique annual phenomenon known as the “mullet run”. During the months of April/May each year, large shoals (measuring up to 10 km in length) of adult flathead mullet would migrate southwards from North Lake and False Bay through South Lake and the Narrows to the mouth of the estuary and out to sea to spawn. Unfortunately due to gradual degradation of the St Lucia system, mullet populations have dwindled over the years and no evidence of the famous mullet run has been observed for nearly two decades. Fortunately relatively healthy flathead mullet populations still exist in the coastal marine environment and other KZN estuaries.
Game Fish Migrations
The coast of KZN is situated in a unique sub-tropical environment falling between the tropical Delagoa bioregion to the north of Cape Vidal and the warm temperate Agulhas bioregion to the south in the Eastern Cape. In summer, migratory or nomadic game fish species arrive from the tropical waters in the north, and in winter warm temperate species move up from the cooler Cape waters in the south. Coastal communities eagerly await the arrival of these migrant species and benefit through tourism and the associated sale of fishing related goods and services.
Whale Shark Migration
The whale shark is the largest fish in the ocean, reportedly attaining lengths of 17 m, although individuals longer than 14 m are now rarely encountered. It occurs in all tropical and most subtemperate waters and is capable of enormous movements across ocean basins. The whale shark is one of the few sharks protected by the Marine Living Resources Act (No. 18 of 1998) in South Africa.
They may appear to be out of sight, but careful scanning of the horizon will often yield spectacles of whales blowing or breaching. In any year several hundred whales migrate along the coast of KZN. Most are one of seven species of filter feeding baleen whales: the blue, sei, fin, Bryde’s, southern minke, humpback and southern right whales. Only one species of large toothed whale, the sperm whale, is known to migrate through the coastal waters of KZN.
ORI - KZN Sharks Board - University of Cape Town
EDTEA • ORI
Fiona MacKay • Sean Fennessy • Bruce Mann • Jade Maggs • Geremy Cliff • Ken Findlay