FIRST RESULTS ON ACADJA-ENCLOS AS AN EXTENSIVE AQUACULTURE SYSTEM (WEST-AFRICA)

Acadja is a fishing method widely practiced in the coastal lagoons of Benin. The principle of this traditional fishery is to set a dense mas s of branches in shallow water, which attract the fishes from the wild . The West African ''Acadja'' is a kind of fish aggregator. The harves t was found variable from 7 to 20 tons of fishes, per hectare and per year. The acadja may also act as a culture system. The study presented here attempts to give evidence of the role of acadja as a potential c ulture system. Two types of experimental design have been compared: en closure with acadja (named ''acadja-enclos'') and enclosure without ac adja used as a control. After 12 months, a biomass equivalent of 8 ton s per hectare has been harvested from the acadja-enclos, equivalent to eight times that of the control system. Among the 18 species of fish harvested, Sarotherodon melanotheron (Cichlidae) represented 79% of th e biomass. Analysis of the fish population showed that young fry had e ntered through the net at the beginning of the experiment and grown in the acadja-enclos. There were no differences in the condition factor between the S. melanotheron from the acadja-enclos and from the wild. The acadja-enclos system appears to be a promising way to exploit the lagoon areas. This principle could be applied in extensive aquaculture or in some aquatic management programs. Further research to understan d the trophic structure of the system and the basis of the exchange me chanism of the food chain in the system is necessary. It could lead to improve it further. This is proposed in the discussion presented here .