EFFECTS OF COMPLETE AND SUPPLEMENTAL DIETS AND ORGANIC POND FERTILIZATION ON PRODUCTION OF MACROBRACHIUM-ROSENBERGII AND ASSOCIATED BENTHICMACROINVERTEBRATE POPULATIONS

Growth and population characteristics of freshwater prawns, Macrobrach ium rosenbergii, fed either a complete diet, a supplemental diet (with fish meal replaced and vitamin and mineral supplements deleted), or t he supplemental diet with an adjunct organic pond fertilization regime were examined. Effects of these treatments on potential forage organi sms (benthic macroinvertebrates) were also evaluated, Juvenile prawns averaging 0.46 +/- 0.49 g were stocked into nine 0.02 ha earthen ponds at 39 520 ha(-1). Treatments were evaluated in triplicate ponds. Ther e were significant differences (P<0.05) between the regression lines f or sample weights over time (growth) in prawns fed the complete diet a nd supplemental diet without organic pond fertilization and between th ose fed the supplemental diet with and without fertilization. There wa s no significant difference (P>0.05) between regression lines for praw ns fed the complete diet and those fed the supplemental diet with an o rganic pond fertilization regime. At harvest, yield, survival, individ ual weight, and feed conversion averaged 943 kg ha(-1), 76%, 31 g, and 3.9, respectively over the three treatments, Deletion of vitamin and mineral supplements and replacement of fish meal in prawn diets was as sociated with a significant reduction (P < 0.05) in total benthic macr oinvertebrate populations, possibly due to increased predatory pressur e by prawns. In ponds in which prawns were fed the supplemental diet, organic fertilization resulted in a significant increase (P< 0.05) in total benthic macroinvertebrates and a 15% increase in average prawn w eight at harvest. Results indicate that prawns may increase predation when essential nutrients are deleted from prepared diets and that the supply of potential forage organisms may be increased by organic ferti lization.