First report: Amazon River Prawn reared in biofloc technology Primeiro relato: Camarão Amazônico criado com tecnologia de bioflocos

The objective of this work was to evaluate the use of biofloc technology to reared Amazon River prawn (Macrobrachium amazonicum). One hundred Amazon River prawn juveniles were divided into two experimental units (250 L), 50 animals per each. Prawns were fed two times per day, with 3% of the prawn biomass. Dissolved oxygen and temperature were performed twice a day. Total suspended solids, pH, alkalinity, ammonia nitrogen, nitrite and nitrate were monitored twice a week. Prawns showed 77.67%, survival, 2.98 feed conversion, weekly weight gain of 0.29 g day, and yield of 822.0 g m after six weeks of rearing. Dissolved oxygen, temperature and pH were suitable for the species, however, for some weeks, ammonia nitrogen and nitrite were higher than the limits recommended for prawn. In conclusion it is possible to use BFT to maintain and rearing Amazon River Prawn (M. amazonicum), however to improve the performance it is necessary to define nutritional requirements, as well improve the management techniques for this species in BFT.

The biofloc technology (BFT) culture is highlighted, due to the interest in closed systems with minimum or no water exchange, with greater biosafety, and environmental and marketing advantages over conventional systems (extensive and semi-intensive). In addition, it can be used at any stage of the culture (larvae, fingerlings and juveniles) as well as to maintain a breeding stock (EMERENCIANO et al. 2013); however, few studies were carried out to evaluate the use of this technology for Brazilian native species, mainly prawns.
Farming of native prawns is a worldwide trend; China and India have been producing Macrobrachium nipponense and M. malcolmsonii, respectively, as alternatives for M. rosenbergii culture (FAO 2016). In Brazil, Amazon River prawn (M. amazonicum) is important for ecology and economy in several regions, being registered from Amapá to the state of Paraná (MORAES-RIODADES & VALENTI 2002, MORAES-VALENTI et al. 2010) and it is a good option for native freshwater prawn culture. Therefore, this species may adapt well for different culture systems (intensive or extensive), due its less-aggressive behavior and its ability to grow in many aquatic environments (MACIEL & VALENTI 2009).
[AJ1] M., G (2013 review and a now-c 328.. The objective of this work was to evaluate the use of biofloc technology to reared Amazon River prawn (Macrobrachium amazonicum).
The study was carried out in the Laboratório de Aquicultura (LAQ), Instituto Federal Catarinense (IFC). One hundred Amazon River prawn juveniles (Macrobrachium amazonicum), average weight 3.88 ± 0.36 g, were divided into two experimental units, 50 animals per each.
Seven days before the stocking with prawn in experimental units (rectangular tanks, 0.72 m² x 0.35 m) with 250 L, water fertilization was carried out with a carbon source (sugar) and powdered diet to keep the carbon:nitrogen (C:N) ratio 10:1, (AVNIMELECH 1999, EBELING et al. 2006 resulting in an initial solids concentration of 100.0 mg L -1 . Seven days after prawn stocking, fertilization was maintained at 10:1 (C:N) to neutralize 40% of the feed nitrogen and to keep the ammonia below 1.0 mg L -1 . Calcium hydroxide was added when alkalinity fell below 30 mg L -1 CaCO 3 , and when necessary, the dose was 10% of the daily ration.
Dissolved oxygen and temperature (YSI55; YSI Incorporated, Yellow Springs, OH, USA) were measured twice a day. Total suspended solids (TSS) (APHA 2005 − 2540 D), pH and alkalinity (APHA 2005 − 2320 B) and settleable solids (Imhoff cone) were monitored twice a week. Fiberglass microfilters (0.6 µm, GF-6 Macherey-Nagel, Düren, Germany) were used for TSS analysis. Ammonia (total ammonia nitrogen − TAN), nitrite-N and nitrate-N were also monitored twice a week according to APHA (2005). Survival, final weight, week weight gain, specific growth rate, food conversion ratio and yield were all determined after six weeks with the formulas described by (JATOBÁ et al. 2014).
Dissolved oxygen, temperature and pH were suitable for species (MACIEL & VALENTI 2009), however, for some weeks, ammonia nitrogen and nitrite were higher than the limits recommended for prawn (DUTRA et al. 2017), other water variables have not their lethal levels determined. Total suspended solids (TSS) may cause gill obstruction, but no one prawn was observed with these characteristics during the experiment, suggesting that TSS levels were adequate (Table 1). 150.9 ± 85.8 Level of nitrogenous compounds (ammonia, nitrite and nitrate) shown oscillation during rearing period (Figure 1).
Which normally occurs during the process of floc formation while the nitrification process had not been established (AVNIMELECH 1999, EBELING et al. 2006. Hardness is an important water quality variable for freshwater prawn, because some physiological processes, such as ecdysis, depend on the availability of Ca and Mg ions (BROWN et al. 1991), its level has increased over time due to calcium hydroxide in puts ( Figure  2).
The growth performance of Amazon river prawn in BFT was better than that observed in prawns reared at different stocking densities (10,20,40  ) was four times lower than that observed in this study (Table 2).   The absence of records of the other zootechnical variables makes it difficult to compare the results, however considering other species of shrimp and prawn grown in BFT (EBELING et al. 2006, JATOBÁ et al. 2014). The specific growth rate was higher than that observed by MORAES-VALENTI & VALENTI (2007) that decrease from 0.6 to 0.4% day -1 in the lowest and highest stocking density, respectively. The data obtained can improve, since little is known about its nutritional, physiological and environmental requirements within this culture system, being necessary the resumption of research with this species. In conclusion it is possible to use BFT to maintain and rearing Amazon River Prawn (Macrobrachium amazonicum), however to improve the performance it is necessary to define nutritional requirements, as well improve the management techniques for this specie in BFT.