Fertilization Effects on Nitrogen and Phosphorus Budgets in Tambaqui (Colossoma macropomum) Pond Grow-Out Systems

This study quantified nitrogen (N) and phosphorus (P) budgets in tambaqui (Colossoma macropomum) cultured for 10 months in fertilized and unfertilized ponds in a tropical region. Juveniles (94 ± 15 g) were stocked at 0.55 fish m−2 in 600-m2 ponds, with four replicates per treatment. Inputs consisted of water, feed, fish, and fertilizer, whereas outputs included harvested fish, sediment, and outlet water. Feed and inlet water were the primary sources of nutrients in the pond systems, while outlet water and fish biomass represented the major nutrient outputs. Total N input was higher in fertilized ponds, whereas total P input was similar between treatments. Feed contributed a larger proportion of total N and P in unfertilized ponds than in fertilized ponds. In fertilized ponds, fertilizer accounted for 19% of total N and 6% of total P. Total N and P outputs did not differ between treatments, although N output showed high variability due to sediment accumulation. Fish recovered 15–20% of N and 22% of P inputs. Greater N use efficiency was observed in unfertilized ponds. Overall, fertilization did not improve nutrient recovery or total nutrient output but reduced feed inputs, suggesting that fertilizer, particularly nitrogen, should be carefully evaluated regarding its environmental and economic relevance in tambaqui pond culture.