PRAWN (MACROBRACHIUM-ROSENBERGII) CULTURE IN EARTHEN PONDS IN THE NILE DELTA, EGYPT - CULTURE PARAMETERS AND COST-BENEFITS

Egyptian customers prefer claw-off freshwater prawns (Macrobrachium ro senbergii). Therefore we designed monoculture and polyculture strategi es for harvesting the highest yield with the smallest claw weight. The investigation studied the average weight (claw-off) of prawns in mono culture ponds as influenced by stocking size, stocking density and sex , as well as the interaction between these parameters. Also the effect s of polyculture were studied, using tilapia and carp at different sto cking rates. After 90-99 days, the average harvest weight (claw-on) wa s 33.0-44.4 g in monoculture and 35.4-40.2 g in polyculture. The prawn biomass (claw-off) averaged 432-1,407 kg/ha in monoculture and 360-46 2 kg/ha in polyculture. Polyculture added 1,826-3,361 kg/ha of fish to the prawn production. Food conversion ratios ranged 2.3-2.8 in monocu lture and 1.9-2.1 in polyculture. Net income per hectare was $946-7102 . The highest rates of return were found in the high density monocultu re strategy when juveniles were stocked, 57.5%, and in the low density polyculture strategy when two postlarvae and 1.25 fish/m(2) were stoc ked, 30.9%.