The fisheries of floodplain river systems in Africa, South America and Asia are similar and their yields can be estimated from various morphological, edaphic and other parameters. There is a close similarity in the ichthyofauna of these regions enabling comparisons between systems to be made. The native fauna of New Guinea (Australasia) is devoid of the primary freshwater fishes that compose the majority of the catch from other regions. Various estimates suggest that the present yield of the Sepik River fishery is about 3000–5000 t year −1 This is approximately 10% of the yield of 30 000–45 000 t year −1 predicted by comparison with African rivers. Much of the present catch is introduced tilapia. Considering the native fish species alone, the present yield is only about 5–7% of that predicted. Fishing effort in the Sepik may be low by comparison with African rivers but the faunal difference is probably the main factor involved. This low yield still represents one of the largest and most important fisheries in the country. Such yeild estimates, even if only rough approximations, are vital for planning and management decisions.