Slopes
The continental slope is the area where the shelf edge descends into the deepsea. The biodiversity of South Africa’s slopes are poorly studied due to the challenges of working below 500 m. Recent camera surveys on the west coast slopes show fishes such as rattails and spiny eels (or rippletails), lantern fish and other deep water sharks and rays. Deep water crabs and urchins have also been seen. In some steep rocky slope areas, exposed to strong currents, deep water coral habitats have been found. No-one has seen the 30-50 m tall deep water coral mounds detected on ship echosounders on South Africa’s slopes, but sampling by dredge or accidental trawling has revealed a diversity of deep water coral species. These corals are being studied by young South African scientists. The study of deep water corals is relevant, not only because they play an important role in fisheries, but because corals are sensitive to changes in ocean temperature and acidity. Deep water corals can provide clues to our past and future climate, particularly fossilised corals.
Key pressures on slopes include fisheries and increasingly there is interest in deepsea mining. Fisheries are the most widespread pressure on slopes, especially those that make contact with the seabed, such as trawling for deepsea fish (hake and kingklip) and crustaceans (prawns, langoustines and crabs). Beyond the shelf edge, South Africa’s slopes are not exposed to many other pressures as yet but reference areas are needed to better study these poorly understood ecosystems, detect change and ensure that existing fisheries benefits are maintained.
Protection for important slope ecosystems is provided in Orange Shelf MPA, Southeast Atlantic Seamounts MPA, Southwest Indian Seamounts MPA, iSimangaliso MPA, Port Elizabeth Corals MPA, Amathole Offshore MPA and Protea Banks MPA.
