Implications of pond fertilization on fish performance, health, effluent, and sediment quality in tambaqui aquaculture

Nutrient input in aquaculture ponds can influence fish growth, health, water quality, and effluent composition. This study assessed the effects of pond fertilization on the performance and health of tambaqui (Colossoma macropomum), as well as on effluent and sediment. Unfertilized and biweekly fertilized replicated ponds were compared. All ponds were stocked with tambaqui juveniles (93.8 ± 15.0 g) at a density of 4,000 fish ha−1 and fed commercial feed. Fertilization did not affect fish yield but improved the feed conversion ratio. After a 10-month trial, three monogenean ectoparasitic flatworm species were identified, with no differences in abundance between treatments. Fertilization reduced water turbidity and increased total and dissolved phosphorus in the effluent, while ammonia levels remained unchanged. Chlorophyll a concentration increased by 59% and zooplankton density by 51% in fertilized ponds, while phytoplankton density was, on average, ∼44% higher during certain months compared to unfertilized ponds. A significant interaction between treatment and time was observed for dissolved oxygen. By the end of the trial, fertilization did not increase organic matter in the sediment. However, it led to higher concentrations of total nitrogen and phosphorus, whereas potassium levels remained unchanged. Overall, pond fertilization improved feed efficiency, did not influence monogenean abundance, and resulted in only minor changes in effluent and sediment quality.