Stocking densities for nursery phase culture of the freshwater prawn Macrobrachium rosenbergii in cages

Effect of stocking density on growth, biomass increase and survival of post larvae of Macrobrachium rosenbergii were evaluated in cages fixed inside an earthen pond. In the primary nursery phase, newly metamorphosed postlarvae (PL) were stocked for 20 days at densities of 2, 4, 6, 8 and 10 PLs l(-1). In the secondary phase (60 days), the densities tested were 100, 200, 300, 400, 600 and 800 PLs m(-2). Prawns were fed with a 35% protein commercial pellet. Survival, final mean weight and average weight gain were significan tly lower (P < 0.05) in high densities of the primary phase, whereas biomas s increase was significantly higher (P < 0.05). In the secondary phase, fin al mean weight and average weight gain were significantly higher (P < 0.05 and P < 0.01, respectively) for densities of 100 and 200 PLs m(-2) than for density of 800 m(-2). Biomass increase was significantly higher (P < 0.01) at densities of 400, 600 and 800 PLs m(-2), when compared to densities of 100 and 200 m(-2), whereas survival differences were not significant. High- density nursery culture of M. rosenbergii in cages seems to be feasible, in order to reduce the costs normally found in conventional nursery systems. (C) 2000 Elsevier Science B.V. All rights reserved.