The analysed species composition, fish growth, and productivity of four polycultures (P75, P78, P87, and P207) with the objective to improve the small reservoir (0.1–5 ha) fishery management and productivity in the Brazilian semiarid region were conducted a experiment. To mimic reservoir conditions, we used 120 and 5,000m2 ponds and evaporation and infiltration water loss was replaced. In addition, manure and fertilizers were used only moderately. The initial biomass of Nile tilapia Oreochromis niloticus, 'tambaqui' Colossoma macropomum, 'curimatã pacu' Prochilodus argenteus, common carp Cyprinus carpio, and 'tucunaré' Cichla ocellaris ranged from 75 to 207kg ha–1. The fish showed low growth rates (<0.01g g–1 d–1) after 75 days of culture (P78 and P87). Tambaqui, tilapia, and curimatã growth decreased after 53 days (P75). In moderate biomass, tambaqui grew less than carp and curimatã did (P207). Tilapia productivity reached 720kg ha–1yr–1 (P78) and fell to 220kg ha–1yr–1 because of the reproductive process (P75 and P207). The carp productivity of 1,600kg.ha–1yr–1 was higher than those of the other fish (P87). The 75kg.ha–1 biomass level (60:30:4:3:3% of tilapia, tambaqui, carp, curimatã, and tucunaré, respectively) optimized fish growth and productivity. The use of monosexed tilapia and tambaqui feed supplementation was indispensable for the success of polyculture.
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