DEVELOPMENT AND POTENTIAL OF NURSERY SYSTEMS IN THE FARMING OF MALAYSIAN PRAWNS, Macrobrachium rosenbergii (de Man)1

Data from various studies associated with the development of intensive indoor nursery systems in South Carolina are provided. Nurseries permit the production of larger juveniles for stocking in ponds or other grow-out systems and thus result in increased production of larger prawns, greater crop value, and improved predictability of yields. In climates where year-round prawn culture is possible the incorporation of a nursery phase should increase profitability. In contrast, in climates with a restricted grow-out season the use of nurseries may be a basic requirement to establish any level of profitability. Growth and survival data are presented from 8 nursery trials conducted at approximate population densities of 300, 1,000 and 1,500 prawns m-2 tank bottom area. Growth was similar at all densities for ˜ one month (mean prawn size, ˜0.2 g) after which time prawn size increased rapidly at the lowest population density (300 m-2). Growth was similar at densities 1,000 and 1,500 m-2 for at least 2 months at which time prawns had reached a mean size of ˜0.50 g. For comparison, prawns reared at the lowest density were 1.32 g after 60 days. Survival rates were generally good: after 30 and 60 days they were ˜99, 98, 90% and 91, 91, 82% for densities 300, 1,000 and 1,500 m-2, respectively. Based on results of our 1978 pond grow-out trials, the stocking of small juveniles (mean size, 0.50 g) or a mixture of postlarvae and juveniles (mean size, 0.65 g) resulted in an estimated profit if initial land and seed stock costs are excluded. From our nursery data we projected that one ha of nurseries stocked at a density of 1,500 prawns m-2 could produce sufficient small juveniles (˜0.5 g) to stock 198 ha of grow-out ponds.