Submarine canyons cut into the shelf on both our west and east coasts. Cape Canyon off Saldahna is our largest shelf breaching canyon and is the same size as America’s Grand Canyon. The Cape Valley off Cape Point is also a large canyon which has sustained the highest fishing effort and catches in our hake trawl fishery for almost a century. Canyons are diverse and productive, with the canyon head often being the most rich and complex area. Rocky walls and margins are home to huge sponges, deep water corals and other fragile habitat-forming species. On the west coast, sandy areas in the canyon often have very dense colonies of animals including brittle stars and mantis shrimps. Nobody has explored the canyons off Port Elizabeth, but a recently discovered canyon near Gxulu, East London has stepped walls hosting brightly coloured deep water corals and fishes. Some of the most charismatic east coast canyon inhabitants in South Africa include our coelacanths, ancient lobe finned fishes thought to be extinct before their discovery off East London in 1938.
Key pressures in canyon ecosystems include bottom fisheries and other activities that impact the seabed such as mining, laying submarine cables, petroleum infrastructure or the anchoring of ships. Canyon margins are fragile and spatial management, such as marine protected areas, play a key role in managing multiple threats.