| Abstract: | During 1978–1980, 18 rearing trials were conducted in 0.25 ha ponds to examine the effects of various stocking strategies on production and economic potential. The strategies tested consisted of stocking: post-larvae only; a mixed population of postlarvae plus juveniles; small juveniles only, at densities ranging from 2.15–8.61 prawns/m2. Prawns were fed Purina Marine Ration 25 once daily and seine-sampled at 4-week intervals throughout the 144–168 day rearing periods. Clear relationships between population structure of the stocked prawns and density versus crop yields and estimated revenues were demonstrated. The stocking of postlarvae resulted in lower production levels and less valuable prawns as compared to stocking a mixture of postlarvae + juveniles or juveniles only populations. Also, survival was more variable (range 59.3–84.5%) and lower (mean 69.6%) when postlarvae were stocked. Greater crop yields were achieved at higher densities, however, mean size and unit value of the crop decreased as density increased. Feed conversions were low and averaged 1.4 (range 0.8–2.2) for all trials combined. Preliminary economic feasibility analyses of the various stocking strategies were performed for situations where ponds and associated facilities were already available. The analyses suggested that positive net revenues were possible if a mixed population of postlarvae and juveniles or juveniles only were stocked at about 6.5/m2 and seed costs were ∑30/1,000 and the crop was marketed as a combination of large whole. |
