Pacific white shrimp and Nile tilapia integrated in a biofloc system under different fish-stocking densities

This study aimed to evaluate the effect of different stocking densities of Nile tilapia, Oreochromis niloticus, integrated with Pacific white shrimp, Litopenaeus vannamei, reared in a biofloc system for 57 days. The performance of both species and the ecological efficiency of the system were evaluated. Four levels of tilapia stocking density were evaluated: 0, 8, 16 and 24 fish per tank (90 L useful volume). The initial weight was 4.8 +/- 0.1 g and 9.6 +/- 0.1 g for shrimp and fish, respectively. The shrimp were fed according to the feed table, and the fish were fed with 1% of fish biomass, stimulating the tilapia to seek food in the biofloc. Results show no difference between average shrimp weight (14.9 +/- 0.6 g) and survival (93.0% +/- 1.0%). Similarly, fish obtained a final mean weight of 61.9 +/- 3.8 g and survival of 91.1 +/- 7.9%. Total yield was higher based on the increase in fish density. The sludge produced per animal biomass (sludge: biomass ratio) decreased as fish density increased (y = - 0.0083xx + 0.5995 r(2) = 0.87). Nitrogen recovery rose linearly with the increase in fish density (y = 0.036xx + 0.2725, r(2) = 0.84), as did phosphorus recovery (y = 0.00711xx + 0.1395, r(2) = 0.91). These results demonstrate the feasibility of increasing yield up to 31.2% by integrating L. vannamei and O. niloticus in a biofloc system. Also, the decrease in sludge: biomass ratio and the higher nitrogen and phosphorus recovery increased the sustainability of L. vannamei rearing in a biofloc system.