Cultivo do camarão de água doce Macrobrachium rosenbergii (De Man 1879) em sistemas simbióticos e bioflocos na fase de berçário

Abstract

The freshwater prawn species M. rosenbergii has shown the need for research to intensify its cultivation, especially in heterotrophic systems with minimal water exchange. In view of this, this work aimed to improve the culture technologies of this species for biofloc and synbiotic systems in the nursery phase. For this, two experiments were carried out. In Experiment 1, different strategies for supplying organic carbon in the culture of this species were tested. The prawn (10.0 ± 2.0 mg) were stored (0.8 PL L−1) for 35 days in an experimental design with five treatments and four replicates: Ct = control; M = molasses (BFT); Mf = molasses pre-treated with Bacillus spp. without and with aeration (synbiotic); RB = rice bran (BFT); and RBf = raw rice bran pre-treated with Bacillus spp., without and with aeration (synbiotic). The prawns were fed five times a day with a diet containing 40% crude protein. The water quality variables remained within the range considered adequate for the species. The synbiotic reduced the mean values of settleable solids. The protein content of microbial flocs (dry weight) differed between RBf (34.07 ± 0.54%) and RB (29.77 ± 0.48%), but was higher in M (43.27 ± 0.76 %). Prawns submitted to RBf showed the best combination of results for the variables final weight (122.85 ± 12.50 mg) and weekly weight gain (22.26 ± 2,97 mg). Once better performance of the RBf was identified, Experiment 2 proposed to investigate the effects of different strategies of synbiotic preparation (fermentation and microbial respiration) on water quality and animal performance. Thus, new post larvae (10.01±2.0 mg, 1.0 PL L−1) were stocked in 20 experimental units for 35 days, design with five treatments and four replicates. Rice bran, probiotics, alkalizing agents and water were used in the preparation of the synbiotic. Each treatment corresponded to a preparation strategy: T12|12 = 12 hours anaerobic and 12 hours aerobics; T12|24 = 12 hours anaerobic and 24 hours aerobic; T24|0 = 24 hours anaerobic only; T24|12 = 24 hours anaerobic and 12 hours aerobic; T24|24 = 24 hours anaerobic and 24 hours aerobic. The results of the quality variables were suitable for the culture of the species. For the variables final average weight (mg) and yield (g m-3), treatments T24|24 (221.3±22 and 195.4±14.6) and T12|24 (218.2±27.6 and 196.2±33.4) were superior to 24| 00 (176.1±24.5 and 151.3±21.6). Thus, we can conclude that it is possible to use the synbiotic system with rice bran in the production of freshwater prawn M. rosenbergii juveniles. Furthermore, the combination of fermentation time and microbial respiration in the synbiotic preparation process has an effect on its quality as a fertilizer and, therefore, on the growth of the animals.