The effective use to zootechnical technique involves a thorough knowledge of the target species. Reproductive characteristics, like growth, behavior and centesimal composition, are some of the main issues for the production the species to be viable in all aspects. This study sheds light on production features of tambaqui, a native species of greater economic interest in Brazil, that are little understood. We investigated the influence of sex and stocking density of rearing systems on centesimal composition and fillet yield at slaughter. Juveniles of tambaqui (75 g, on average) were grown in dug ponds for 10 months in two different stocking densities of production systems (4 and 6 tons per ha). Each animal was considered a sampling unit, totaling 164 repetitions (77 males and 87 females). The analysis to determine the centesimal composition were moisture, total lipids, crude protein and ash. The measurements undertaken were total length, loin, head, width, full weight, fillet weight, residual weight (weight of the whole animal minus fillet weight), fillet weight and yield (fillet weight divided by the weight of the whole animal). The aim was to investigate for differences in features of commercial interest between different stocking densities and sexes. The results showed differences between sexes and stocking densities, which requires identification of the most interesting features for the market for later adoption of rearing systems of monosex populations and stocking densities in fish farmin g.