Stocking densities in cage rearing of Amazon river prawn ( Macrobrachium amazonicum) during nursery phases

Abstract

Amazon river prawn ( Macrobrachium amazonicum) is widely distributed along Brazilian rivers, being one of the native species with a major cultivation potential. This study evaluated stocking densities during primary and secondary nursery phases for M. amazonicum in cages, regarding survival, growth, biomass, food conversion and productivity. The experiment was carried out in 12 cages of 0.5 m 2 (iron frames recovered with polyethylene mash) placed inside of a 1500 m 2 earthen pond. Early metamorphosed postlarvae (PL) (0.009 ± 0.006 g) were stocked for 28 days (primary nursery phase), at densities of 4, 6, and 8 prawns L −1. In the secondary nursery phase (62 days), densities were 200, 400 and 800 prawns m − 2 (0.12 ± 0.01 g). Prawns were fed commercial pellets (35% crude protein). Water quality parameters were within the adequate range for freshwater prawn culture. In the primary nursery phase, the productivity for density of 8 PL L −1 was two times greater compared to 4 PL L −1 (6.17 and 3.35 juveniles I L −1, respectively) and differed significantly ( P < 0.05). In the secondary nursery phase, mean survival was above 95% and did not differ significantly, while mean weight differed ( P < 0.05) for the densities of 200 (0.44 g) and 800 (0.36 g) prawns m −2. The highest biomass (143.6 g) was registered at 800 prawns m −2 density and differed significantly ( P < 0.01) from lower densities. The productivity of juveniles II also differed significantly among densities, being about four times greater at 800 prawns m −2 compared to lower densities. Net income was positive only at densities greater than 400 prawns m −2, being highest at a density of 800 prawns m −2. Thus, on an experimental basis, the nursery system for M. amazonicum at high densities in cages showed to be viable.