Tuna and tuna fishing extend over most of the tropical waters of the world oceans, especially, this study of the Indian Ocean and the fish and the fishing vessels are highly mobile. No country can deal in isolation with the problems of its tuna fishery and of any tuna fishery in its waters, without collaborating with other countries. This cooperation is often best established through some formal international mechanism. The essential requirements are for information-on the resources, the fishery, the trade-and to identify where management actions are needed to consore the resources or to maintain the economic or social function of the fishery. These will also usually require some form of international mechanism. With the changes in the Law of the Sea, the siuuation in respect of management of tuna-considered among the highly migratory species, requirng special treatment-has also changed. At present there are both uncertainty regarding tuna management and political arguments as to how such management can be best implemented. Bearing this in mind, together with the fact that only few tuna stocks have shown clear evidence of serious depletion through over-exploitation, present emphasis will be placed on information requirements. This study included compiling the data necessary to review the state of stoks in the Indian Ocean tuna fishing grounds. Information on the resources-where the fish are, their quantity, their movements, etc. is important, whether in planning development of new fisheries, or considering the need for collaboration with other countries (in ascertaining to what extent their catches may affect catches of the natoinal fleet) or for conservation measures. A major source of information is the statistics of for conservation measures. A major source of information is the statistics of catch and fishing effort from existing commercial vessels. These need to be assembled for all fisheries on the same stock on an oceanwide basis. The statistical data also need to be analysed and intepreted, and combined with biological data(e.g., on growth, mortality and migration rates) to provide information that is intelligible and useful for administrators and other decision-makers. This must also be undertaken on a resource-wide or ocean-wide basis. Finally, because of the world-wide similarities in the methods of datching, processing and marketing fish, there is a particular tut not exclusive need in those countries just beginning to develop their tuna fisheries-to have ready access to a syntheis of information on tuna, tuna biology and tuna fisheries and tuna fisheries economics and management on the Indian Ocean.