Africa is a continent of great rivers: the Congo (which is the only major river to cross the equator twice), the (great gray-green, greasy) Limpopo (as Rudyard Kipling called it), the Niger, the Nile, the Orange, and the Zambezi, to name a few.    Some of the world’s great lakes are in Africa: for example, Kivu, Nyasa (Malawi), Tanganyika, and Victoria. Africa’s coastline climate, with the Atlantic ocean on the west and the Indian ocean on the east, ranges from Mediterranean, to tropical and equatorial, to temperate. For certain African peoples, fishing and gathering various freshwater or saltwater species has been an important source of food for millennia. One notable feature of African cooking is the use of fish and shrimp that have been preserved by drying, salting, or smoking. (Though in many dishes they are used only as a seasoning.) This practice undoubtedly dates from pre-historic times, when it the only way to keep a bountiful catch for future use. Today, imported salted codfish from Scandinavia (called stockfish) is found in shops and groceries all over Western and Central Africa.