open ocean
This open ocean or pelagic environment is the realm of phytoplankton, microscopic plants that are responsible for half of the world’s oxygen production. Phytoplankton are the foundations for marine ecosystems, and they are eaten by animal plankton such as tiny larvae of most marine creatures including fish. Little fish eat bigger fish that are in turn eaten by larger predators such as tuna, swordfish, sharks, whales, dolphins and seabirds. Small pelagic fish such as sardines and anchovy are an important food source for humans but also feed many other animals and are often referred to as forage fish.
The seabed and open ocean ecosystems are connected and these connections are closer in shallower water (particularly on the shelf) and where seabed structures influence the flow of water such as at seamounts, canyon margins and at the shelf edge. Even though the open ocean may seem similar there are areas of difference such as areas where there are frequent fronts or eddies that may increase food availability. Pressures in open ocean ecosystems include fisheries such as those targeting forage fish and predators such as tunas and sharks. Fishing gears used in such fisheries include purse seine, mid water trawl, line and pole and pelagic long lines. South Africa has a proud tradition of effective fisheries management which is needed to ensure sustainable use. Accidental capture of animals such as seabirds, turtles and some shark species can be minimised by special management measures such as tori lines to reduce bird bycatch, turtle excluder devices and special hooks. Marine Protected Areas can also help protect important feeding areas for open ocean travellers such as turtles, whales and seabirds.
Some protection for for open ocean ecosystems and pelagic species will be provided in the Orange Shelf MPA, Agulhas Front MPA, Cape Canyon MPA, Robben Island MPA, Agulhas Bank Complex MPA, Addo Elephant National Park MPA, Protea Banks MPA, Amathole Offshore MPA, Southeast Atlantic Seamounts MPA and Southwest Indian Seamounts MPA.
