CULTIVATION OF A FRESHWATER PRAWN (MACROBRACHIUM ROSENBERGII) WITH NILE TILAPIA (OREOCHROMIS NILOTICUS) AND WITH THE COMMON CARP (CYPRINUS CARPIO), IN DIFFERENT DENSITIES

Abstract

A quantitative analysis on polyculture of the freshwater prawn (Macrobrachium rosenbergii) with tilapia (Oreochromis niloticus) and with common carp (Cyprinus carpio), was carried out aiming at assessing the productivity in different stocking rates. Three different tilapia/prawn and carp/prawn densities were tested: 500/500; 750/750 and 1,500/1,500 individuaIs per pond. The experiment was conducted in six 1,000 m² (50 m x 20 m) earthen ponds between September, 1994 and March, 1995. Random samples were taken fortnightly in order to assess total length and body weight averages and the feeding quantity was corrected. Fishes were fed pelletized diet with 22% protein, five days a week, at 3% of the biomass. Growth at length and weight curves, the weight/Iength relationship and economics curves were obtained for each treatment. Prawns growth were influenced more by their own stocking rate than by that of the fish, being highest in the lowest stocking rate in polyculture with tilapia. The highest productivity was shown in the highest density (1,500 tilapia + 1,500 prawns) which yielded 4,240 kg.ha^-1.yr^-1 of tilapia and 842.2 kg.ha^-1.yr^-1 of prawn. The highest economic profit was not reached until the end of the experiment, which indicates that the period of culture was too short in all cases and that the experiment should be continued to reach maximum profits.