Desempenho zootécnico de juvenis de camarão de água doce Macrobrachium rosenbergii em sistema de bioflocos

Abstract

Biofloc technology has become available as an alternative to promote a sustainable and environmentally friendly aquaculture, thus improving water quality and production indexes. Several studies have been performed with focus on penaeidae shrimp rearing in biofloc systems, however, few studies are focused on the freshwater prawns Macrobrachium rosenbergii. Therefore, the general aim of this study is to assess the zootechnical performance of juvenile freshwater prawns Macrobrachium rosenbergii in biofloc system and collect information, that makes possible to improve commercial production technics on this species in heterotrophic systems. In order to achieve that, three experiments were performed at the Marine Biological Station of Federal University of Rio de Janeiro, Mangaratiba, RJ (MBS). The juveniles of M. rosenbergii were purchased from Farm Santa Helena, located in Silva Jardim, Rio de Janeiro, then, the juveniles were brought to the MBS and acclimated for 7 days in cisterns with treated freshwater, under continuous aeration and fed with commercial diets of 35% CP. In the first experiment the influences of stocking densities (150 e 250 m2), and sources of organic carbon (sugarcane molasses, brewery residue) were assessed regarding the performance of M. rosenbergii juveniles in biofloc systems, during a period of 43 days. The results demonstrate that it is possible to stock the animals in densities of 150m2 and use brewery residue as a source of organic carbon in order to improve water quality and zootechnical performance. In the second experiment, three commercial diets were evaluated (30, 35 e 40% CP) for feeding M. rosenbergii in biofloc systems, during 44 days, in order assess the possibility of using food with lower crude protein levels in the diets of juveniles. Results demonstrate that it is possible to reduce protein levels in commercial diets of Macrobrachium rosenbergii prawns from 40 to 30% CP in biofloc systems, however, further studies are needed regarding water quality monitoring, to improve the productivity indexes. In the third experiment, the effect of using artificial substrate for the rearing of M. rosenbergii in biofloc systems was assessed for 44 days. The addition of artificial substrate in biofloc systems do not improve the process of water nitrification and centesimal composition of the tissue of prawn M. rosenbergii. The decrease in water quality and the high levels of total suspended solids in biofloc systems with artificial substrates, do not improve survival and feed conversion of prawns, when compared with clear water systems, clear-water systems with artificial substrate, and biofloc systems.