Carrying capacity for Nile tilapia production in net cages in tropical reservoirs during an extreme drought

This study assessed the production carrying capacity for Nile tilapia (Oreochromis niloticus) in net cages in reservoirs of the Brazilian semi-arid region during a supra-seasonal drought. It used the phosphorus mass balance models to estimate nutrient assimilation, with phosphorus concentration limits in the water column were set at 30 μg.L⁻¹, according to Brazilian legislation, and 60 μg.L⁻¹ for eutrophied environments. In the Santa Cruz reservoir, the phosphorus assimilation capacity was 5,848 kg.year⁻¹ at 60 μg.L⁻¹, while in Umari it was 572.7 kg.year⁻¹ at 30 μg.L⁻¹ and 4,620 kg.year⁻¹ at 60 μg.L⁻¹. The carrying capacities were 680 tonnes in Santa Cruz at 60 μg.L⁻¹, and in Umari, 63 tonnes at 30 μg.L⁻¹ and 508 tonnes at 60 μg.L⁻¹. Despite higher phosphorus loading in Umari, Santa Cruz showed greater capacity at 60 μg.L⁻¹ due to its larger water volume. The study highlights the importance of reservoir morphometry and hydrological parameters for aquaculture sustainability during extreme droughts, and uses mass balance models to propose practices that balance production and environmental conservation.