More than 3000 species of freshwater fishes are found in the South American rivers, most of which belong to the Amazon region while only about 700 species have been found in the rivers and lakes of North America (J. D. Allan 1995).  In Africa too, fish species diversity is as high as that found in the South America. It has been estimated that the number of species in Lake Victoria alone is as large as around 2000. The tropical Asian fish fauna constitutes a substantial part of the total lotic fish community. The Indochinese peninsula supports 930 species of native freshwater fishes belonging to 87 families (Kottelat 1989). A number of tropical Asian freshwater fish communities are shared with those in African riverine ecosystems, both at the family as well as at the generic level. Cyprinids, some Siluriformes catfishes, Channids, Mastecembelids and Notopterids are shared between the two regions. At the generic level, Anabas, Barilius, Clarias, Garra, Labeo and Mastecembelus are common genera that are found both in African as well as in Asian rivers. Some fishes which have been introduced from Africa like the Tilapia have become widespread all over Southern Asia and have in some places also replaced in dominance some native populations. Some families like the Cichlids, which are very common in Africa, have restricted distributions in Asia e.g. Etroplus is found only in the Indian subcontinent.  Studies on the distribution of groups of species show that while Africa has a predominance of Characids and Cichlids, Asia is predominated by Cyprinids and Balitorids.
 

References