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In a 30-day experiment, Farfantepenaeus brasiliensis PL 25 (25 AE 10 mg;17.9 AE 1.6 mm) were raised in nine circular £oating cages with a stocking density of 1000 shrimp m À 3 . Three treatments were evaluated:(1) culture in BFT system plus a commercial feed supply (BFT1CF); (2) culture in BFT system without feed supply (BFT) and (3) culture in clear water with feed supply (control). Post-larvae (PL) ¢nal weight (218.9, 236.5 and 176.0 mg, for BFT1CF, BFT and control respectively), ¢nal biomass (17.9, 15.7 and 8.2 g) and weight gain (193.9, 211.5 and 151.0 mg) were similar in the BFT regardless of whether they were fed a commercial diet (P40.05), but were both signi¢cantly higher than the control (Po0.05). Survival (81.5%, 67.0% and 84.8% respectively) and ¢nal length did not di¡er between treatments (P40.05). The bio£oc analysis identi¢ed ¢ve main microorganism groups: protozoa (ciliate and £agellate), rotifers, cyanobacteria (¢lamentous and unicellular) and pennate diatoms. Free living bacteria and attached bacteria in bulk were 25.73 AE 8.63 and 0.86 AE 3.17 Â 10 6 mL À 1 respectively. Proximate analysis in the bio£oc indicated high levels of crude protein (30.4%). Results con¢rmed favourable nutritional quality of bio£oc, and enhanced growth and production of F. brasiliensis PL in bio£oc systems.

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Farfantepenaeus paulensis juveniles (72 ± 24 mg), were reared in a suspended microbial flocs system and fed practical diets containing increasing amounts of crude protein (250, 300, 350, 400 and 450 g kg−1 CP). Development of microbial flocs was promoted by high aeration rates and fertilization with wheat bran and molasses. Flocs were composed of detritus in the form of flocculated matter colonized by heterotrophic bacteria, cocoid and filamentous cyanobacteria, flagellate and ciliate protozoa and rotifers. Proximate composition analysis of the suspended microbial floc showed CP levels of 304 g kg−1. After 45 days, mean shrimp survival were above 89%, with no significant differences between treatments. Shrimp fed diets with 350 g kg−1 or higher CP content achieved significant higher (P < 0.05) final weight (0.66–0.68 g), weight gain (0.58–0.61 g) and instantaneous growth rate (0.049–0.050), with feed conversion rates (2.17–2.30) significantly lower (P < 0.05). Results show that, when rearing is carried out in a suspended microbial flocs system, dietary CP levels can be kept at 350 g kg−1. Furthermore, results confirm that microbial‐based systems allow shrimp culture without compromising the surrounding environment and shows the possible reduction of production costs and fish meal dependence.

No abstract