Effects of Population Density on Growth and Survival of Macrobrachium rosenbergii REARED IN RECIRCULATING WATER MANAGEMENT SYSTEMS1

This is the authors' abstract. We don't add key points for this paper.

Growth and survival were monitored among juvenile Macrobrachium rosenbergii (de Man) reared at different population densities in recirculating water management systems. Four cylindrical tanks, each with a bottom area of approximately 2.5 m2, and two rectangular raceways with bottoms about 2.8 m2in area were used in the experiments. The cylindrical tanks were stocked with 0.12 g prawns at densities of 10 to 200 animals/m2of bottom area. Juveniles of similar size were stocked in the raceways at about 200 and 400/m2in one study, and slightly smaller animals (0.07 g) were reared at densities approximating 200 and 500/m2in a second raceway experiment. Both survival and growth varied inversely with population density in all experiments. After 112 days, a mean weight of 9.2 g and survival rate of 82% were obtained among the prawns stocked at 10/m2in a cylindrical tank compared to a mean weight of 3.6 g and survival rate of 50% for those stocked at 200/m2. However, survival was good (nearly 80%) even at 200 prawns/m2for the first 60 days of the study. Similarly, in the raceways growth was relatively slow at the high population densities tested (200 to 500/m2), but survival was excellent for at least the first 6 weeks of rearing (>93% at 200 and 400/m2; about 83% at 500/m2). Survival rates remained high (≥80%) for up to 90 days at 200/m2but had decreased to 56% at 500/m2by this time. Substantial variations in prawn sizes and growth rates were observed in all experiments. The degree of variation in size within a cohort, which generally increased with mean size, appeared to be unaffected by population density. This suggests that the marked differences in individual growth rates observed within cohorts may be inherent.