Alkaline water improves the growth and antioxidant responses of pacu juveniles (Piaractus mesopotamicus)

Abstract This study aimed to evaluate the effect of different water pH levels on the growth performance and oxidative stress responses of pacu juveniles. Pacu were subjected to four different water pH levels (5.5, 6.5, 7.5 and 8.5) for 45 days in recirculation aquaculture systems. The best growth performance occurred at a water pH of 8.5. At a water pH of 8.5, in general, alkalinity, nitrite and un-ionised ammonia were higher and plasma ions Na+ and K+ were lower than at other water pH values. Total ammonia was higher at a water pH of 5.5. Juveniles exposed to acidic water pH (5.5 or 6.5) showed a lower muscle antioxidant capacity against peroxyl radicals (ACAP) and glutathione S-transferase (GST) activity. Water pH did not affect survival, blood glucose and pH, haematocrit, plasma Cl−, and the muscle content of protein thiols (PSH) and thiobarbituric acid reactive substances (TBARS). In conclusion, a water pH of 8.5 is recommended for pacu production systems, since fish presented higher growth and antioxidant statuses at this pH.