Tropicultura (Jan 2002)
Experiment on an Integrated Ricefish Polyculture System (6 Species, 1- 2 fish/m2) in the Mekong Delta
Abstract
Our ricefish polyculture (6 species) results at two stocking densities (1 and 2 fish/m2) show that: The water quality in a ricefish polyculture system, such as water temperature (29.1 – 29.0 °C), water pH (6.6 – 6.7), water transparency (18.0 – 20.8 cm), dissolved O2 (4.7 – 4.6 ppm), CO2 (22.8 – 23.1 ppm), COD (11.9 – 12.7 ppm), are similar at both densities and acceptable for the 6 tropical fish species. Ammonium and phosphorus concentrations are statistically higher at 1 fish/m2 (0.4 and 0.2 ppm). The primary productivity is similar for both densities (6.5 – 6.8 g O2/m3/day) and suitable for fish culture. The phytoplankton biodiversity is relatively high and at the same level for both treatments (74 – 63 taxa), but the densities of phytoplankton, of zooplankton, and the biomass of zoobenthos are lower at the highest density (2 fish/m2), probably due to a higher predation by fish.The fish yield (808 kg/ha) at 2 fish/m2 is higher than at 1 fish/m2 (482 kg/ha). The cost ratio benefit (1.84) and the cost ratio profit (1.81) for farm households at 1 fish/m2 are lower than those values at 2 fish/m2 (2.1 and 2.05 respectively). Regarding the aquaculture extension program, the model of the ricefish polyculture (6 species) system with the stocking density of 2 fish/m2 could be extended in the rice fields to improve farmer's income in the Mekong delta.
