Yield of freshwater prawn Macrobrachium rosenbergii (Decapoda) after removing its females from a continuous polyculture system with tilapia (Pisces) in Puerto Rico

Presence of freshwater prawn females is an important biological factor causing size variation during the growing process and negatively affecting production. Removal of the females during the growing cycle would improve yield efficiency. This study determined how yield, survival, and mean weight of freshwater prawn Macrobrachium rosenbergii are affected by removal of females from a continuous polyculture system with red tilapia. In treatment 1, only the captured commercial-size female prawns were harvested monthly, harvest starting on day 130 after initial stocking. In treatment 2, all captured distinguishable female prawns, regardless of their size, were removed. Juvenile prawns (1.2 g) and fingerling red tilapia (32 g) were stocked at five prawns and one fish per square meter. The prawn yield (mean weight) was 1,988 kg/ha (40 g) in T1, and 2,346 kg/ha (40 g) in T2. No significant effects on prawn yield, final mean weight, feed conversion ratio or mortality resulted from continually removing female M. rosenbergii from the polyculture. However, there were significant differences in mean weight (T1 = 54 g and T2 = 59 g) and percentage (T1 = 85% and T2 = 78%) of prawn reaching commercial size.