Tolerance of pirarucu juveniles to increasing ammonia concentration in a closed environment

The objective of this work was to evaluate the tolerance of pirarucu (Arapaima gigas) juveniles to increasing concentrations of ammonia in the water. Eight fish (2.6 +/- 0.4 kg and 70.5 +/- 4.1 cm length) were evenly distributed in four tanks (0.80.9x2.6 m) with 410 L of water buffered with Na2PO4 (0.1 M) and HCl (0.1 M), where they were kept for 33 days. Ammonia concentrations in the fish blood plasma and in the water were determined by the salicilate method. Plasma glucose and ammonia levels increased proportionally to the concentration of ammonia in the water. Pirarucu juveniles tolerate high concentrations of ammonia in the water.