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Resume The fisheries of thc ccntral delta of the Nigcr river have been intensivcly cxploited for many ycars. The analysis of a 20-year record of landings of fish shows vcry large fluctuations in production which decreases regularly from 87,000 metric tons in 1969-70 to 37,000 mctric tons in 1984-85. Two factors may explain this phenomenon: the advent of drought in Africa and/or thc increase of fishing cffort. In thc first case, plots of annual catches and lost watcr, computed according to thc hydrologie cycle of the delta (from July to June), are highly correlated. In fact, fishcd quantities make up by 69% of thc fishes under one ycar old. In the second casc, old data shows that thc fishing effort probably increased considerably. Neverthelcss it sccms that this intcnsc fishing effort has few ncgativc results on the total of thc catches. Actually, it seems that fishermen are in troublc: decline in individual catch which drops from 1,900 kg in 1966 to 740 kg per year in 1989, necessity of complcmcntary activities like agriculture, nccessity for one part of the family to movc to other lakes in Mali or to other countries. The crisis, which comes from a natural phenomenon, has developed sociological and economical perturbations. ln fact thc dccrease of floodplains induces a reduction of fishing areas and the advent of troublcs between villages or families. In another conncction, the lack of control in accessing the fishery by traditional authorities and a population increase, could have produced the transition from 43,000 fishermen in 1966 to 63,000 in 1989. The division of falling catches is therefore cvcn more difiicult.

Influence de l'hydrologie sur l'évolution des pêcheries du delta central du Niger, de 1966 à 1989