The Indian Ocean coastline of mainland Africa is over 9 500 km long and comprises the tropical coasts of Somalia, Kenya, Tanzania and Mozambique, plus the subtropical and warm-temperate Indian Ocean coastline of South Africa. The regional marine fisheries catch (Indian Ocean catch only for South Africa) is about 200 000 t, more than 80% of which is taken from Mozambique and Tanzania. Regional fisheries are dominated by intense artisanal and subsistence sectors, although there are also several commercially important industrial fisheries, mostly targeting lobsters, prawns and squid. No reliable species lists exist for individual countries of tropical Africa, but 11257 marine species are recorded from the western Indian Ocean region (island states included) and 11980 species from South Africa (including Atlantic coast). Comparing these lists by taxonomic group, and with similar. lists for Europe (29713 known:species) reveals great disparities in taxonomic coverage and large gaps in the data, especially for smaller sized organisms. It is concluded that less than half of species actually present in East Africa have been described. Existing data are also based largely on shallow-water surveys and the benthic invertebrates of deeper waters, especially those of the continental slope and abyssal zone, remain virtually unexplored.