Culture of the Nile tilapia “Oreochromis niloticus” in biofloc system with different stocking densities

SUMARY This work aimed to evaluate the water quality and the growth performance of Nile tilapia (Oreochromis niloticus) cultured in bioflocs system with different stocking densities. The experiment was conducted at the Aquaculture Station of the Federal Rural University of Pernambuco, Brazil, during 128 days. Fish 123.0 ± 0.6 g were stocked in twelve 800 L circular tanks in a completely randomized design with three treatments (D15, D30 and D45, related to densities of 15, 30 and 45 fish.m-3) and four replicates. Among water quality variables, dissolved oxygen had a significant effect (P≤0.05) between the densities, with the lowest concentration (3.97 mg O2.L-1) for the highest tested density (45 fish.m-3). The total ammonia present statistical difference between the D15 and the others; and also, the nitrite, between density 15 and 45 fish.m-3, but both at a directly proportional relationship with the increasing of stocking density, showing higher average concentrations of 2.56 and 3.26 mg.L-1 (NH3+NH4 and NO2,respectively), in 45 density fish.m-3. The growth performance in the 45 fish.m-3 density showed the best results, with yield of 16.6 kg.m-3, with significant difference between treatments (P≤0.05). Survival was higher than 90% at the three tested densities. Bioflocs technology can be employed in intensive culture of Nile tilapia O. niloticus in the growout phase, using stocking densities up to 45 fish.m-3.