PROMISES AND DEADLOCKS OF CHANGES IN FISH CULTURE SYSTEMS IN THE "CENTRE-OUEST". (Ivory Coast)

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SUMMARY: In 92, the pertinence of semi-intensive extended models was obvious in suburban areas, however, new technical changes were not excluded. To avoid exploring too many possibilities, research of new technical solutions adapted to small fishfarmers has harmonised its methods and its purposes, the underlying basis of this process is presented in the following paper. The results of six prizewinners in a tilapia-culture show organised between fish-farmers in suburban areas during 94 and 95 are presented and analysed, they bring to light many new elements enabling us to grasp ongoing changes. The best net yield with hand-sexed male Oreochromis niloticus exceeds 9 t/ha/year while the average yield is over 6 t/ha/year, the minimum average fish-size allowed being 350 g. The homogeneity of these results indicates an excellent technical command of fish farming although inputs are various. In line with these results and others, orientations for the analysis of fertilised environment are proposed. Special attention is given to urea which often appears as an accessible means of balancing nitrogen deficient organic fertilisation. Possibilities of polyculture in such environment are briefly recalled, particulary those related to the association of Heterotis niloticus and Heterobranchus isopterus. Experimented results of fingerlings production in irrigated rice field enable us to consider the possibility of reducing the suface area of fry and fingerling cropping in some places. Subsequently, the various experiments integrating acadja are reviewed. Although acadja turned out to be unadapted to local conditions, it presents technically interesting results. Further more, currently investigated means of improving extensive models are exposed: the use of urea, better integration of rice cropping and fish farming and the remarkable contribution of Ctenopharyngodon idella to the initial polyculture. Conditions for the development of these innovations are discussed.

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