Experiment on an integrated rice-fish polyculture system.
Abstract An experiment was carried out in Vietnam on an integrated rice-fish polyculture system with three species: common carp (Cyprinus carpio), Nile tilapia (Oreochromis niloticus) and silver barb (Barbonymus gonionotus). Agricultural by-products were used as supplementary feed at a rate of 2-3% total body weight of fish per day. The total fish yield (823 kg ha-1) and fish production (988 kg ha-1 yr-1) at 2 fish m-2 were significantly higher (p<0.05) than at 1 fish m-2 (453 kg ha-1 and 544 kg ha-1 yr-1, respectively). The cost : benefit ratio (1.80) and the cost : profit ratio (1.75) for farm household income at 1 fish m-2 were lower than at 2 fish m-2 (2.08 and 2.02, respectively). This system should be adopted by aquaculture extension programmes to improve rural farmers' income when the market prices for common carp, tilapia and silver barb are sufficiently high to obtain a benefit at the end of the culture cycle.