The Agulhas Bank (/əˈɡʌləs/, from Portuguese for Cape Agulhas, Cabo das Agulhas, "Cape of Needles") is a broad, shallow part of the southern African continental shelf which extends up to 250 km (160 mi) south of Cape Agulhas before falling steeply to the abyssal plain.
It is the ocean region where the warm Indian Ocean and the cold Atlantic Ocean meet. This convergence leads to treacherous sailing conditions, accounting for numerous wrecked ships in the area over the years. However the meeting of the oceans here also fuels the nutrient cycle for marine life, making it one of the best fishing grounds in South Africa.
Map of the Agulhas Bank centred on the Outeniqua Basin
|Realm||Temperate Southern Africa|
|Area||116,000 km2 (45,000 sq mi)|
|Elevation||-50 to -200 m|
|Oceans or seas||Atlantic Ocean, Indian Ocean|
The Agulhas Bank stretches approximately 800 km (500 mi) along the African coast, from off Cape Peninsula (18°E) to Port Alfred (26°E), and up to 250 km (160 mi) from it. The bank is 50 m (160 ft) deep near the coast and reaches 200 m (660 ft) before dropping steeply to 1,000 m (3,300 ft) on its southern edge. The shelf spans an area of 116,000 km2 (45,000 sq mi) with a mean depth slightly over 100 m (330 ft).
The National Spatial Biodiversity Assessment 2004 recognised 34 biozones nested within 9 bioregions (of which four were offshore). The National Biodiversity Assessment 2011 replaced these ecozones and biozones with the terms ecoregions and ecozones. In 2011, the Agulhas Ecoregion was divided into four distinct ecozones: Agulhas inshore, Agulhas inner shelf, Agulhas outer shelf, and Agulhas shelf edge. 33 different benthic habitats types were identified on the Agulhas Bank.
There are dozens of warm temperate reefs along the coast of the Agulhas Ecoregion spanning from 5–30 m (16–98 ft) below sea level. Many rocky sub-tidal reefs are of aeolianite or sandstone origin, but granite, quartzite and siltstone reefs are also present. The Agulhas reefs are very heterogeneous and include several possible different sub-types. Some of the reefs are within protected areas, but only a few of those protected areas include protection from fishing.
The Agulhas Current flows south along the African east-coast and along the south-eastern edge of the bank. It then retroflects back into the Indian Ocean south-west of the bank. This retroflection results in intense eddy activities such as meanders, eddies, and filaments. In upper layer water, the Agulhas rings and eddies move warm and salty water into the large South Atlantic gyre, which exports it to the tropics. In the lower ocean layers water is transported in the opposite direction.
Cyclonic eddies is another source of edge upwelling west of Port Elisabeth. Plumes of warm surface water migrate onto the bank along its eastern edge, providing subtropical surface water from the Indian Ocean. In summer, easterly winds can intermittently drive coastal upwelling along the South African south coast. The Agulhas Bank is dominated by westerly winds and most of the upwelling on the bank is related to the interaction of the Agulhas Current on the eastern edge, but easterly winds do occur, especially in summer and fall, and can generate local upwelling cells.
As the current is diverged away from the coast, dynamic processes draws an onshore Ekman layer of cold water from below the warm shelf-edge flow. In spring and summer, at a depth of 100 m (330 ft), a semi-permanent ridge of cold water is present on the eastern and central shelf.
In summer, there is mixture of subtropical water separated by thermoclines from cool waters, but there is a considerable seasonal variation. On the shelf, bottom waters exhibit characteristics of the central Indian Ocean in the east and central Atlantic Ocean waters in the west.
As the Agulhas Current flows south along the African east coast, it tends to bulge inshore frequently, a deviation from the current's normal path known as Agulhas Current meanders (ACM). These bulges are occasionally (1-7 times per year) followed by a much larger offshore bulge, known as Natal pulses (NP). Natal pulses move along the coast at 20 km (12 mi) per day. An ACM can bulge up to 20 km (12 mi) and a NP up to 120 km (75 mi) from the current's mean position. The AC passes 34 km (21 mi) offshore and an ACM can reach 123 km (76 mi) offshore. When the AC meanders, its width broadens from 88 km (55 mi) to 125 km (78 mi) and its velocity weakens from 208 cm/s (82 in/s) to 136 cm/s (54 in/s). An ACM induces a strong inshore counter-current.
Large-scale cyclonic meanders known as Natal pulses are formed as the Agulhas Current reaches the continental shelf on the South African east-coast (i.e. the eastern Agulhas Bank off Natal). As these pulses moves along the coast on the Agulhas Bank, they tend to pinch off Agulhas rings from the Agulhas Current. Such a ring shedding can be triggered by a Natal pulse alone, but sometimes meanders on the Agulhas Return Current merge to contribute to the shedding of an Agulhas ring.
Agulhas rings are large anticyclonic eddies or warm core rings of ocean water that are pinched off the Agulhas Current along the eastern edge of the Agulhas Bank from where they move into the South Atlantic. As the Agulhas Current reaches the east coast of South Africa, large solitary meanders known as Natal pulses form at irregular intervals. 165 days after the appearance of a Natal pulse, an Agulhas ring is formed off Durban. The Agulhas rings are among the largest eddies in the world and play an important role in the Agulhas Leakage, the transport of warm water from the Indian Ocean to the Atlantic Ocean, which affects the global climate.
The average diameter of the Agulhas rings is 320 km (200 mi), but they can reach 500 km. They extend down to the ocean floor; circulate at 0.3–1.5 m/s (0.98–4.92 ft/s); and move into the South Atlantic at 4–8 km (2.5–5.0 mi)/day. Only half of the Agulhas eddies that leave the Cape Basin manage to cross the Walvis Ridge and those that do tend to lose half their energy before reaching the ridge within six months. The Agulhas rings transport an estimated 1-5 Sv (millions m²/s) of water from the Indian Ocean to the South Atlantic.
The Agulhas rings are thought to be of global climatic importance. Their delivery of warm water from the Indian to the Atlantic Ocean can control the rate of thermohaline overturning of the entire Atlantic. Other factors contribute to various degrees to the inter-ocean exchanges in the region, including filaments from the Agulhas Current and intrusions of water from Antarctica. Cold, cyclonic eddies have been observed in the southwestern Atlantic. Based on model simulations, researchers have found that the interaction of the Agulhas Current and the eastern edge of the bank can result in the Agulhas rings.
The provenance of ocean sediments can be determined by analysing terrigenous strontium isotope ratios in deep ocean cores. Sediments underlying the Agulhas Current and Return Current have significantly higher ratios than surrounding sediments. Analyses of cores in the South Atlantic deposited during the Last Glacial Maximum (LGM, 20 000 years ago), show that the Agulhas leakage (shedding of Agulhas rings) was significantly reduced. It has been hypothesised that the reason for this was that the Agulhas Current was stronger which resulted in a more eastward retroflection and therefore less leakage. However, analyses of such cores south of Africa show that the trajectory of the current was the same during the LGM and that the reduced leakage must be explained by a weaker current. Consequently, it can be predicted that a stronger Agulhas Current will result in its retroflection occurring more eastward and an increased Agulhas leakage.
Compared to the Agulhas Current, the Benguela Current on the west and south-west coast of Africa is more intense and steadier. Its dynamic southern upwelling system is driven by the prevailing northward winds that produce an intense off-shore Ekman transport. Most of this upwelling is concentrated to a few upwelling cells in the southern region: Namaqua (30°S), Cape Columbine (32.5°S), and Cape Peninsula (34°S). The wind is most intense from October to February, and the contrast in sea surface temperature between the open sea and the shelf is most prominent during summer.
Coastal upwelling s also common on the western bank, but the more stable atmospheric condition results in larger cold water plumes that sometimes merge to form a continuous upwelling regime along the South African south-west coast. This upwelling zone is the southernmost extension of the Benguela Current Large Maritime Ecosystem. The Agulhas Current regularly flows around the southern tip of the bank and brings warm water to the western bank along the bank's western edge. Regularly, the mesoscale eddies from the east interact with the Benguela upwelling system on the African west coast.
Floating south along the South American continental slope, the Deep Western Boundary Current (DWBC) carries North Atlantic Deep Water (NADW) into the South Atlantic. At about 8°S and at a depth of 2,200–3,500 m (7,200–11,500 ft), the DWBC breaks into anticyclonic eddies during periods of strong meridional overturning circulation. One such NADW eddy was observed in 2003 and the researchers speculated that a deeply penetrating Agulhas ring pinched it off the NADW slope current. Spinning at 20 cm/s (7.9 in/s), these deep-water eddies move around the southern tip of the Agulhas Bank and into the Indian Ocean. Most of the NADW flow (more than 7 Sv) meanders east around the Agulhas Plateau together with the surface Agulhas Return Current, but a smaller portion (3 Sv) continue north along the African east-coast as the Agulhas Undercurrent. Of 89.5 Sv released from the North Atlantic, 3.6 Sv leaves the South Atlantic south of the Agulhas Bank. However, 0.9 Sv recirculate in the basin north of the Walvis Ridge for centuries, of which 50-90% end up flowing south of the Agulhas Bank within 300 years, increasing the net inter-oceanic exchange with 4.1-4.5 Sv.
The oldest rock found along the coastline of the Agulhas Bank are eugeosynclinal sediments of the up to 3 km (1.9 mi) thick Kaaimans Group deposited during continental rifting some 900 million years ago (Mya). The proto-South Atlantic closed during the Saldanian orogeny to form part of the supercontinent Gondwana (700-600 Mya). The Cape granites were emplaced and the Kaaimans Group rocks were folded and thermally metamorphosed during this period. The formation of the main basin in the Cape Province commenced 570 Mya and lasted for 200 My. The Table Mountain Group is 4 km (2.5 mi) thick and an erosional unconformity marking its base is composed of both terrestrial and marine sediments. Synclines along the coast of the southern Cape contains sediments from the Bokkveld Group.
The Cape Fold Belt (CFB) rocks and the Karoo Basin were deposited 450 Mya; the Cape Supergroup 450-300 Mya during a series of transgression-regression cycles. Pan-African thrusts were reactivated 270-215 Mya to form the CFB which was then part of a continuous fold belt that developed during the Gondwanide orogeny together with Sierra de la Ventana (Argentina), Pensacola Mountains (East Antarctica), and Ellsworth Mountains (West Antarctica). In the late Carboniferous and early Jurassic, the Karoo Supergroup was deposited in the Karoo Basin north of where the CFB is located today, and covering nearly two-thirds of present-day South Africa.
Basaltic lavas were extruded 183 Mya to form the Karoo large igneous province; a volcanism caused by the Bouvet hotspot which is linked to the Gondwana break-up. The Bouvet hotspot was located in or near present-day South Africa from the late Triassic 220 mya and until the Africa-Antarctica breakup 120 mya. The Bouvet hotspot track stretches south-east from the African continent, near the South Africa-Mozambique border, and east of the AFFZ down to Bouvet Island/Bouvet Triple Junction in the South Atlantic. 100 Mya, the region where the triple junction was located passed over the hotspot, resulting in a continuous eruption that lasted to about 94 Mya and the seafloor spreading that still separates Antarctica, Africa, and South America.
The Agulhas-Falkland Fracture Zone (AFFZ) stretches 1,200 kilometres (750 mi) across the South Atlantic. It is one of the largest and most spectacular fracture zones on Earth. It developed during the Early Cretaceous as West Gondwana (=South America) broke up from Africa. The AFFZ is characterized by a pronounced topographic anomaly, the Agulhas Ridge (41°S,16°E-43°S,9°E) which rises more than 2 km above the surrounding sea floor. The only equivalent in size are the neighbouring Diaz Ridge and the Falkland Escarpment. The Agulhas Ridge is unique because it was not formed during the continental breakup during the Cretaceous and because it separates oceanic crusts of different age, and not oceanic crust (~14 km thick) from continental crust (25 km thick).
North of the (AFFZ) is the Outeniqua Basin which is a complex system of sub-basins separated from each other by faults and basement arches; there are several smaller fault-bounded sub-basins in the north (Bredasdorp, Infanta, Pletmos, Gamtoos, and Algoa) and a distinctively deeper sub-basin in the south (the South Outeniqua Basin.) The sedimentary fill of these basins developed as the northern edge of the Falkland Plateau separated from the South African southern margin during the early Cretaceous.
The Diaz Marginal Ridge (DMR) separates these basins from the AFFZ. The DMR is buried under 200–250 m (660–820 ft) of sediments and sedimentary rocks and 150–200 m (490–660 ft) of this sedimentary material is undisturbed Cretaceous sediments younger than the oldest Cretaceous sedimentary rocks in the Southern Outeniqua Basin. The DMR must therefore have formed after the initial West Gondwana breakup 130-90 Mya. The DMR probably formed when new, hot oceanic crust slid past old, cold continental crust and the contrast in temperatures induced a thermal uplift.
As West Gondwana drifted away from Africa roughly 125 Myr, the South Atlantic seafloor formed between them and magnetic anomalies north of the AFFZ reflects phase of the seafloor spreading. South of the AFFZ traces can be found of how the Falkland Plateau and the Agulhas Bank moved relative to each other. On a modern map, the Falkland Plateau can still be rotated and fitted into the Natal Valley in the Indian Ocean east of South Africa. The Agulhas Plateau is located southeast of the shelf, separated from it by the Agulhas Passage (through which the Agulhas Current flows.)
One of the largest known slumps occurred on the south-eastern edge of the Agulhas Bank in the Pliocene or more recently. Stretching from a depth of 190–700 m (620–2,300 ft), the so-called Agulhas slump is 750 km (470 mi) long, 106 km (66 mi) wide, and has a volume of 20,000 km3 (4,800 cu mi). It is a composite slump with proximal and distal allochthonous sediment masses separated by a large glide plane scar. In the western part, the sediments are dammed by basement ridges, but, in the eastern part, they have spread into the Transkei Basin. A series of slump scarps along the western edge of the shelf are 18–2 Mya, but covered by younger sediments brought there by the Benguela upwelling.
Anatomically modern humans evolved around 200 kya. The genetic diversity in the human lineage is relatively low, which indicate one or several population bottlenecks late in our lineage. It has been estimated that the population was limited to maybe 600 individuals during the MIS 6 glacial stage (195-125 kya), one of the longest cold periods in the Quaternary of Africa. A technological and behavioural revolution that occurred globally about 50 kya led to a cultural complexity which happened in South Africa around 120-70 kya.
The Cape Floral Region is a thin coastal strip and a botanic hotspot which developed at the confluence of the Benguela Upwelling and Agulhas Current. According to what professor Curtis Marean calls the "Cape Floral Region – South Coast Model" for the origins of modern humans, the early hunter-gatherers survived on shellfish, as well as geophytes, fur seal, fish, seabirds, and wash-ups found on the exposed Agulhas Bank. The bank slopes into the sea and a reconstruction of how the coastline has changed over 440 kya shows that the coast during the Pleistocene was located as far as 90 km (56 mi) from the present coast.
The present South African southern coastal plain (SCP) is still separated from the rest of Africa by the Cape Fold Belt. During glacial maxima the sea-level dropped 120 metres (390 ft). This not only left large parts of the Agulhas Bank exposed, which greatly expanded the area of the SCP, but it also reconnected the SCP to the rest of Africa by the shallow water shelves, which broke the isolation of the SCP. Modern humans evolved on the SCP and the fluctuation in sea-levels would have resulted in a significant variation in selective pressure. No fossil records are known from the now submerged shelf, but a series of key fossil sites along the coastal margin of the present SCP provide earliest traces of anatomically modern humans and the use of marine resources.
South Africa began oil exploration on the Agulhas Bank in the 1980s. Of more than 200 offshore wells in South Africa, most are found on Bredasdorp Basin on the Agulhas Bank.
The Agulhas Bank is also significant for fisheries who use demersal trawling, demersal longline fishing, and midwater trawl fishing on the bank. Squid and small pelagic fishes are also caught. Before the introduction of the EEZ, foreign fisheries used roch-hopper gear trawling on the bank.
Most of the catches are short-lived shelf-zone pelagic species and more long-lived deep-water species. The large populations of sardine and anchovy also present on the shelf follow an annual cycle. Anchovy spawn on the western Agulhas Bank in early summer while the sardines span over a broader season and area — eggs are transported by currents to the nursery area in the St Helena Bay on the South African west coast from where juvenile then migrate back to the Agulhas Bank to spawn.
South Africa has a relatively large fishing industry mostly catching pelagic pilchard and anchovy and demersal Hake on the south and western coasts. Though the east coast has fewer commercial fisheries, the large human population along there has resulted in overexploitation of coastal fish and invertebrate stocks by recreational and subsistence fishers. A small aquaculture industry produces mussels and oysters offshore.
Several pelagic species are heavily harvested by the commercial fleet: purse-seine fishery is used to catch sardines, anchovies, and round herring; mid-water trawl fishery to catch horse mackerel and chub mackerel; pelagic longline and pole fishery to catch tunas and swordfish; while hook and line are used inshore to catch squid and teleost species, including snoek and geelbek. All these species are relatively common and are considered having an important role in the ecosystem.
There are at least 12,914 marine species in South Africa, but small bodied species are poorly documented and the abyssal zone is almost completely unexplored. Almost a quarter of South Africa's coast line is protected, excluding deeper water. A third of the marine species are endemic to South Africa (though poor levels of taxonomic research in adjoining countries probably affects the apparent endemism.) The degree of endemism varies considerably among taxa: Bryozoa 64%, Mollusca 56%, Echinodermata 3.6%, Porifera 8.8%, Amphipoda 33%, Isopoda 85%, or Cumacea 71%. Fisheries are one of the major threats to the biodiversity of the Agulhas Bank.
Copepods comprise 90% of the zooplankton carbon on the Agulhas Bank, and are thus an important source of food for pelagic fish and juvenile squids. The population of Calanus agulhensis, a large species that dominates the copepod community in terms of biomass, has a center of distribution on the central Agulhas Bank. Since 1997 the copepod biomass on the central Agulhas Bank has declined significantly while the biomass of pelagic fish has increased significantly. While it is likely that predation has played an important role in the copepod decline, global warming (sea surface temperature and Cholorphyll A abundance) is believed to have contributed to a smaller population.
The shelf edge along the bank's southern tip is subject to sporadic upwelling. This slope and its surrounding seamounts are the spawning ground for sardine, anchovy, and horse mackerel. Eddies help transport water inshore and link the spawning habitat with important nursery areas. Eggs and larvae laid by the anchovy are transported via the Good Hope Jet to Africa's southwestern coast where they mature. Young anchovies then return to the Agulhas Bank to spawn. Young sardine and anchovy congregate along the west coast between March and September before they migrate to their spawning grounds on the Agulhas Bank. Sardines of intermediate age are present on the western Agulhas Bank between January and April before migrating to KwaZulu-Natal for winter. The spawning on the Agulhas Bank takes place 30–130 km (19–81 mi) offshore from September to February.
The bank is the spawning area of deep reef fish species, including the threatened endemic red steenbras (Petrus rupestris). Other species have been overexploited, including daggerhead seabream or dageraad (Chrysoblephus cristiceps), black musselcracker (Cymatoceps nasutus), and silver kob (Argyrosomus inodorus).
The main food source for African penguins (Spheniscus demersus) is anchovy and sardine which they forage between Cape Columbine and the central Agulhas Bank. The birds have colonies on Dassen Island, on the South African west coast, and Bird Island, on the south coast. African penguins breed opportunistically, following the anchovy and sardine: from February to September on the Western Cape but from January to July on St Croix Island off Eastern Cape. After breeding, the birds forage further offshore: 10–15 km (6.2–9.3 mi) off the western coast and up to 40 km (25 mi) from their colonies off Eastern Cape.
In 2005, when Korean and Philippine vessels started longline fishing along the edges of the Agulhas Bank, seabird bycatch became a huge problem. Large numbers of albatrosses and petrels were killed — in average 0.6 birds per 1000 hooks, but up to 18 birds per 1000 hooks were reported. Since 2007, however, more restrictive permit conditions for foreign-flagged fleets and the use of birds scaring lines have decreased the number of killed birds by 85%.
Cape fur seals are present along the South African coast. Fur seals are protected in South Africa since 1893 although a small number are occasionally culled to protect sea birds. Many seals are caught in fishery nets and boat propellers, but the seals are also regularly accused of stealing fish from the fisheries. Sharks are known to prey on them, but in 2012 a cape fur seal was observed preying on and consuming a mid-sized blue shark.
51 species, or more than 50%, of the recognized species of cetaceans are present in the southern African subregion (between the equator and the Antarctic ice edge), of which 36 have been sighted in South African and Namibian waters.
A vulnerable population of fish-eating killer whales are present offshore on the Agulhas Bank. Observations peak in January while few are sighted in April and May. The killer whales move in pods of 1-4 individuals and are mostly sited over the shelf edge off the south-east coast. An analysis of killer whale mtDNA has shown that there was a peak inter-oceanic migration events during the Eemian interglacial period, 131-114 kya. This peak coincides with a period of maximal Agulhas leakage which promoted a rapid and episodic interchange of killer whale lineages. During this period killer whales and other marine top predators, such as the great white shark, colonised the North Atlantic and Mediterranean by following their prey — bluefin tuna and swordfish.
A vagrant Commerson's dolphin — a species with two isolated populations, one along the southern coast of Argentina and the other around the Kerguelen Islands — was sighted on the Agulhas Bank in 2004. It is not known from which population the sighted individual stems. The Kerguelen Islands are located 4,200 km (2,600 mi) and South America 6,300 km (3,900 mi) from the Agulhas Bank, but the west-ward direction of the Antarctic Circumpolar Current would force the dolphin to swim against the current from the Kerguelen Islands.
The Agulhas Bank Complex Marine Protected Area is an offshore marine protected area on the continental shelf lying approximately 39 nautical miles southeast of Cape Agulhas off the Western Cape in the Exclusive Economic Zone of South Africa.Agulhas Current
The Agulhas Current is the western boundary current of the southwest Indian Ocean. It flows down the east coast of Africa from 27°S to 40°S. It is narrow, swift and strong. It is suggested that it is the largest western boundary current in the world ocean, with an estimated net transport of 70 Sverdrups (Sv, millions m3/s), as western boundary currents at comparable latitudes transport less — Brazil Current (16.2 Sv), Gulf Stream (34 Sv), Kuroshio (42 Sv).Agulhas Passage
The Agulhas Passage is an abyssal channel located south of South Africa between the Agulhas Bank and Agulhas Plateau. About 50 km (31 mi) wide, it connects the Natal Valley and Transkei Basin in the north to the Agulhas Basin in the south and is the only near-shore connection between the south-western Indian Ocean and South Atlantic Ocean.Cape Agulhas
Cape Agulhas (; Portuguese: Cabo das Agulhas [ˈkaβu ðɐz ɐˈɣuʎɐʃ], "Cape of the Needles") is a rocky headland in Western Cape, South Africa.
It is the geographic southern tip of the African continent and the beginning of the dividing line between the Atlantic and Indian Oceans according to the International Hydrographic Organization.Historically, the cape has been known to sailors as a major hazard on the traditional clipper route. It is sometimes regarded as one of the great capes. It was most commonly known in English as Cape L'Agulhas until the 20th century. The town of L'Agulhas is located near to the cape.Cape Peninsula
The Cape Peninsula (Afrikaans: Kaapse Skiereiland) is a generally rocky peninsula that juts out into the Atlantic Ocean at the south-western extremity of the African continent. At the southern end of the peninsula are Cape Point and the Cape of Good Hope. On the northern end is Table Mountain, overlooking Cape Town, South Africa. The peninsula is 52 km long from Mouille point in the north to Cape Point in the south.
The Peninsula has been an island on and off for the past 5 million years, as sea levels fell and rose with the ice age and interglacial global warming cycles of, particularly, the Pleistocene. The last time that the Peninsula was an island was about 1.5 million years ago. Soon afterwards it was joined to the mainland by the emergence from the sea of the sandy area now known as the Cape Flats. The towns and villages of the Cape Peninsula and Cape Flats now form part of the City of Cape Town Metropolitan Municipality.
The Cape of Good Hope is sometimes given as the meeting point of the Atlantic and Indian Oceans. Thus the west coast of the Peninsula is invariably referred to as the "Atlantic Coast", but the eastern side is known as the "False Bay Coast". It is at Cape Point (or the Cape of Good Hope) that the ocean to the south is often said to be divided into the Atlantic Ocean to the west, and the Indian Ocean to the east. However, according to the International Hydrographic Organization agreement that defines the ocean boundaries, the meeting point is at Cape Agulhas, about 200 km (120 mi) to the southeast.Similarly, Cape Point is not the fixed "meeting point" of the cold Benguela Current, running northwards along the west coast of Africa, and the warm Agulhas Current, running south from the equator along the east coast of Africa. In fact the south flowing Agulhas Current swings away from the African coastline between about East London and Port Elizabeth, from where it follows the edge of the Continental shelf roughly as far as the southern tip of the Agulhas Bank, 250 km (155 miles) south of Cape Agulhas. From there it is retroflexed (turned sharply round) in an easterly direction by the South Atlantic, South Indian and Southern Ocean currents, known as the "West Wind Drift", which flow eastwards round Antarctica. The Benguela Current, on the other hand, is an upwelling current which brings cold, mineral-rich water from the depths of the Atlantic Ocean to the surface along the west coast of Southern Africa. Having reached the surface it flows northwards as a result of the prevailing wind and Coriolis forces. The Benguela Current, therefore, effectively starts at Cape Point, and flows northwards from there, although further out to sea it is joined by surface water that has crossed the South Atlantic from South America as part of the South Atlantic Gyre. Thus the Benguela and Agulhas currents do not strictly "meet" anywhere, although eddies from the Agulhas current do from time to time round the Cape to join the Benguela Current.Curtis Marean
Curtis W. Marean is a professor of archaeology at Arizona State University.In a 2010 article in Scientific American, Marean explained how anatomically modern humans survived the MIS 6 glacial stage 195-123 thousand years ago, a period during which the human population was limited to only a few hundreds breeding individuals. During this period, sea levels dropped more than a hundred meters and the sloping South African Agulhas Bank was transformed into a plain on which humans could survive on shellfish and wash-ups from the sea.He is currently the associate director of the Institute of Human Origins in Tempe, Arizona.Fishing in Benin
Fishing in Benin, which had been carried on largely by Ghanaian fishermen, is gaining importance at Cotonou (where a fishing port was opened in 1971) and other coastal centers. Under an agreement with the Senegal government, Senegalese fishermen introduced deep-sea-fishing methods to the Beninese, and a national fishing company was established as a joint venture with Libya.
Exports of fish commodities amounted to nearly $1.9 million in 2003. Lagoon and river fishing remain of primary importance; of an estimated catch of 41,900 tons in 2003, 30,000 tons were from inland waters. The production of fish steadily declined during the 1980s due to over fishing and ecological degradation, but started increasing by the mid-1990s. In 2003, fishery products accounted for 2.8% of agricultural exports.Fishing industry by country
This page lists the world fisheries production for 2005. The tonnage from capture and aquaculture is listed by country.Genypterus capensis
Genypterus capensis (Smith, 1847), commonly known as kingklip, is a species of cusk eel occurring along the Southern African coast from Walvis Bay in Namibia to Algoa Bay in South Africa, and is closely related to Genypterus blacodes from New Zealand. The species grows to a maximum length of 180 cm, a weight of 15.0 kg, and is one of the most popular fish items on South African menus. Despite appearances it is not closely related to the eel family
Kingklip occur at depths from 50 – 500 m, but usually in the range 250 – 350 m. They are bottom-dwelling and inhabit rocky localities on the shelf and upper continental slope. Juveniles are more often found in shallow waters. They feed on dragonets, mantis shrimps, hake, squid, and various fish species. Spawning usually takes place from August to October. The species is oviparous, with oval pelagic eggs floating in a gelatinous mass. Their dorsal soft rays number 150, while the anal soft rays number 110. The head and body are normally pink to orange in colour, with dark blotches dorsally.
Andrew Smith, the redoubtable Scots explorer and zoologist, first described the kingklip in 1847 from a specimen caught near the entrance to Table Bay and named it Xiphiurus capensis ('xiphos'=sword, 'oura'=tail). His description was published in "Illustrations of the zoology of South Africa", an account of the natural history objects he collected during his expedition into the interior of South Africa in 1834-36. It was also described by the German naturalist Johann Jakob Kaup in 1858 and named Hoplophycis lalandi.Kingklip were heavily exploited in the 1980s, and populations have not yet recovered so that some precautions are in place. Being relatively slow-growing and long-lived, stocks cannot sustain the pressure of targeted fishing, and are taken only as a bycatch species. It is one of the economically important species to South African fisheries. The related species from New Zealand, Genypterus blacodes, has made its way to South African markets and is retailed as kingklip. Kingklip's lack of obvious scales has sparked lively and ongoing debate in Jewish circles as to whether it qualifies as kosher or treif.The South African Journal of Marine Science, in Volume 8, Issue 1 of 1989, published a description of the species' larval development in the southern Benguela Current. The distribution of kingklip larvae was studied over a 12-month period, and yielded data on spawning areas and breeding seasons. The researchers concluded that there are different spawning strategies for the western Agulhas Bank and the West Coast. On the Agulhas Bank, spawning is initiated by a decrease in sea surface temperature, whereas on the West Coast, spawning only occurs when upwelling has decreased i.e. between June and December. Females grow larger than males in both areas, but are slower growing.'Genypterus' is derived from 'genyos' = face, jaw and 'pteron' = wing, finGood Hope Jet
The Good Hope Jet is the northward-running shelf edge frontal jet of the Southern Benguela Current off the Cape Peninsula of South Africa's west coast. The jet, an intrusion of water from the Agulhas Current, was first described by South African oceanographers, Nils Bang and W.R.H. (Bill) Andrews in 1974. This warm water jet forms a sharp front as it comes into contact with the colder upwelled water over the shelf and plays a key role in carrying fish eggs and larvae from their food-poor Agulhas Bank spawning grounds to inshore nurseries.HMS Pandora (1833)
HMS Pandora was a 3-gun brig of the Royal Navy, in service from 1833 to 1862.
From 20 December 1850 to 5 June 1856 her captain was Commander Byron Drury, under whose command she spent four and a half years surveying the New Zealand coast.
Soundings made off the Cape of Good Hope at the Agulhas Bank in 1851.
Carried out survey work of North Island, New Zealand.
In December 1854, surveyed Sumner Bay, including the bar and mouth of the Avon-Heathcote Estuary for the Canterbury Provincial Council. Drury wrote a report and produced a detailed chart of the area, with soundings.Thomas Kerr her Master.Hawkins Bank
Hawkins Bank is a large, submerged bank off the Mascarene Plateau. It is considered a dependency of Mauritius (in terms of fishing banks, much like Saya de Malha Bank, Nazareth Bank and the Soudan Banks). The bank is abundant with fish and Mauritian vessels often fish in the waters in and around the bank.L'Agulhas
L'Agulhas is the most southern coastal village and holiday resort in Africa, located within the Cape Agulhas Municipal (CAM) area at the southernmost tip of the African mainland. It is situated next to the town of Struisbaai and about 30 kilometres (20 mi) south of the regional centre of Bredasdorp. The name "Agulhas", Portuguese for "needles", is said to have been given to the cape because the compass-needle was seen to point due north, that is, with no magnetic deviation. The Agulhas Bank is reputed to be the richest fishing area in the Southern Hemisphere. Some of the older residents and documents refer to the town as by its former name Cape Agulhas or Cape L'Agulhas or simply Agulhas which were the names that referred to this town before it was changed to L'Agulhas to avoid confusion when the Bredasdorp Municipality changed its name to The Cape Agulhas Municipality (CAM).
Tourist interests and activities include: A visit to the Lighthouse with a view from the tower and a walkway along the seafront to the new most southern African monument and a place where two oceans meet at the foot of Africa. A little further along the walkway is the shipwreck of Meisho Maru. Tourists also enjoy the local fyhbos plants, bird watching, hiking, swimming in the local tidal pools or a game of Jukskei on Saturday mornings. Other interests are visiting arts and craft shops, local wine sales, shops and restaurants or enjoy a meal at one of the best local fish restaurants in the area. L’Agulhas is a peaceful town and a ‘get away’ from busy city living.Nazareth Bank
Nazareth Bank is a large submerged bank in the Indian Ocean.Ocean bank
An ocean bank, sometimes referred to as a fishing bank or simply bank, is a part of the seabed which is shallow compared to its surrounding area, such as a shoal or the top of an underwater hill. Somewhat like continental slopes, ocean banks slopes can upwell as tidal and other flows intercept them, resulting sometimes in nutrient rich currents. Because of this, some large banks, such as Dogger Bank and the Grand Banks of Newfoundland, are among the richest fishing grounds in the world.
There are some banks that were reported in the 19th century by navigators, such as Wachusett Reef, whose existence is doubtful.Sardine run
The sardine run of southern Africa occurs from May through July when billions of sardines – or more specifically the Southern African pilchard Sardinops sagax – spawn in the cool waters of the Agulhas Bank and move northward along the east coast of South Africa. Their sheer numbers create a feeding frenzy along the coastline.
The run, containing millions of individual sardines, occurs when a current of cold water heads north from the Agulhas Bank up to Mozambique where it then leaves the coastline and goes further east 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. In 2003, the sardines failed to 'run' for the third time in 23 years. While 2005 saw a good run, 2006 marked another non-run.The shoals are often more than 7 km long, 1.5 km wide and 30 metres deep and are clearly visible from spotter planes or from the surface.
Sardines group together when they are threatened. This instinctual behaviour is a defence mechanism, as lone individuals are more likely to be eaten than large groups.Sepia simoniana
Sepia simoniana is a species of cuttlefish native to the western Indian Ocean. Its natural distribution stretches from Cape Town to Agulhas Bank, north to northern Kenya and southern Mozambique. It is also present in the Saya-de-Malha Bank. S. simoniana usually lives at depths of less than 100 m, although it has been recorded down to 190 m.S. simoniana grows to a mantle length of 185 mm.The type specimen was collected off Simon's Bay, South Africa. It is deposited at the Zoologisches Museum in Berlin.Slump (geology)
A slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or rock layers moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface. Causes of slumping include earthquake shocks, thorough wetting, freezing and thawing, undercutting, and loading of a slope.
Translational slumps occur when a detached landmass moves along a planar surface. Common planar surfaces of failure include joints or bedding planes, especially where a permeable layer overrides an impermeable surface. Block slumps are a type of translational slump in which one or more related block units move downslope as a relatively coherent mass.
Rotational slumps occur when a slump block, composed of sediment or rock, slides along a concave-upward slip surface with rotation about an axis parallel to the slope. Rotational movement causes the original surface of the block to become less steep, and the top of the slump is rotated backward. This results in internal deformation of the moving mass consisting chiefly of overturned folds called sheath folds.
Slumps have several characteristic features. The cut which forms as the landmass breaks away from the slope is called the scarp and is often cliff-like and concave. In rotational slumps, the main slump block often breaks into a series of secondary slumps and associated scarps to form stairstep pattern of displaced blocks. The upper surface of the blocks are rotated backwards, forming depressions which may accumulate water to create ponds or swampy areas. The surface of the detached mass often remains relatively undisturbed, especially at the top. However, hummocky ridges may form near the toe of the slump. Addition of water and loss of sediment cohesion at the toe may transform slumping material into an earthflow. Transverse cracks at the head scarp drain water, possibly killing vegetation. Transverse ridges, transverse cracks and radial cracks form in displaced material on the foot of the slump.
Slumps frequently form due to removal of a slope base, either from natural or manmade processes. Stream or wave erosion, as well as road construction are common instigators for slumping. It is the removal of the slope's physical support which provokes this mass wasting event. Thorough wetting is a common cause, which explains why slumping is often associated with heavy rainfall, storm events and earthflows. Rain provides lubrication for the material to slide, and increases the self-mass of the material. Both factors increase the rate of slumping. Earthquakes also trigger massive slumps, such as the fatal slumps of Turnagain Heights Subdivision in Anchorage, Alaska. This particular slump was initiated by a magnitude 8.4 earthquake that resulted in liquefaction of the soil. Around 75 houses were destroyed by the Turnagain Slump. Power lines, fences, roads, houses, and other manmade structures may be damaged if in the path of a slump.
The speed of slump varies widely, ranging from meters per second, to meters per year. Sudden slumps usually occur after earthquakes or heavy continuing rains, and can stabilize within a few hours. Most slumps develop over comparatively longer periods, taking months or years to reach stability. An example of a slow-moving slump is the Swift Creek Landslide, a deep-seated rotational slump located on Sumas Mountain, Washington.
Slumps may also occur underwater along the margins of continents and islands, resulting from tidal action or a large seismic event. These submarine slumps can generate disastrous tsunamis. The underwater terrain which encompasses the Hawaiian Islands gains its unusual hummocky topography from the many slumps that have taken place for millions of years.
One of the largest known slumps occurred on the south-eastern edge of the Agulhas Bank south of Africa in the Pliocene or more recently. This so-called Agulhas Slump is 750 km (470 mi) long, 106 km (66 mi) wide, and has a volume of 20,000 km3 (4,800 cu mi). It is a composite slump with proximal and distal allochthonous sediment masses separated by a large glide plane scar.Turritella declivis
Turritella declivis is a species of sea snail, a marine gastropod mollusk in the family Turritellidae.