GROWTH, SURVIVAL, AND BIOCHEMICAL-COMPOSITION OF FRESH-WATER PRAWNS MACROBRACHIUM-ROSENBERGII FED NATURAL FOOD ORGANISMS UNDER CONTROLLED CONDITIONS

Under production conditions freshwater prawns Macrobrachium rosenbergi i are supplied nutrients by a combination of prepared diets and natura l pond organisms. For maximum production efficiency and profitability it is important that the nutritional contributions of natural foods be identified and quantified. In this study the relative importance of f orage organisms previously identified as important natural foods for p rawns in ponds were evaluated under controlled conditions. Juvenile pr awns (average weight 1.80 +/- 0.06 g) were stocked into 18 37.5-L, aqu aria at a density of 10 prawns per tank. The six dietary treatments te sted were: 1) unfed (negative control); 2) commercially prepared diet (positive control); 3) oligochaetes; 4) chironomids; 5) zooplankton; a nd 6) a combination of the Latter three. Each treatment was evaluated in triplicate aquaria for 7 wk, The growth rate of prawns in the unfed treatment was statistically lower than in fed treatments (P < 0.05). There were no significant differences (P > 0.05) between growth rates and survivals among prawns in the five fed treatments. Selective reten tion of arachidonic acid (20:4n-6), eicosapentanoic acid (22:5n-3), an d docosahexanenoic acid (22:6n-3) in unfed prawns likely indicates the relative nutritional importance of these fatty acids, Comparisons of whole-body fatty acid and amino acid concentrations of prawns and food organisms indicate that zooplankton and oligochaetes may have the mos t appropriate biochemical compositions as prawn food sources.