| Abstract: | A nursery-reared population of juvenile freshwater prawns (Macrobrachium rosenbergii) averaging 0.11 ± 0.058 g was size graded through a 4-mm bar grader producing a numerically 53% upper size population (0.25 ± 0.086 g). These were stocked into triplicate earthen ponds (0.04–0.07 ha each) at densities of 39,540, 59,300 and 79,100/ha, grown for 131 to 134 d, and fed a specially formulated diet. An additional three ponds were stocked at 39,540/ha and fed a commercial sinking catfish feed. Density had a significant effect on average whole body wet weight at harvest but no significant effect on either total yield, survival, or feed conversion. Mean wet weight was significantly higher for prawns stocked at 39,540/ha (34.3 g) than that for those stocked at either 59,300/ha (26.7 g) or 79,100/ha (263 g). The direct relationship between the percentage of small males and increasing density usually seen with ungraded populations was not evidenced in the size-graded populations. Average total yield ranged from 1,041 to 1,662 kg/ha for stocking densities from 39,540 to 79,100/ha. Differences in overall mean wet weight resulted from differences in mean wet weights for orange claw and no claw males and berried and open females, not from differences in morphotype distributions. These differences resulted in significantly higher percentages of tails within the larger count categories and higher revenues for prawns stocked at 39,540/ha. Feed type had no significant effect. Projected net revenues suggest that prawns need to be marketed and sold as a whole product. |
