Effect of CO2 on acid-base regulation and growth performance of basa catfish (Pangasius bocourti)

This study aims to evaluate the effects of different carbon dioxide levels on blood physiological parameters and growth performance of basa catfish (Pangasius bocourti). The study included two experiments, (1) change of fish blood physiological parameters at different CO2 levels such as 1%, 2%, 3% CO2;and (2) effect of CO2 levels on fish growth performance. In the first experiment, blood samples were collected at 0, 1, 6, 24, 48, 72, 96 and 168 hrs. after equilibration to investigate pHe, pCO2, [HCO3-] and [Cl-] in plasma. The grow-out experiment was set up for 60 days and fish was weighed at the day 0, 30 and 60. The results showed that, after 1 hr. of CO2 exposure, pHe wassignificantly decreased (7.51±0.01 in control fish and 7.28±0.02 in the fish exposed to CO2 3%, this parameter was recovered after 6 hrs. pCO2 and [HCO3-] increased at all CO2 exposed groups. After 168 hrs., pCO2 and [HCO3-] in plasma of 3% CO2 exposed fish were significantly increased and reached the values of 20.7±1.35 mmHg and 22.2±1.16 mM, respectively; those pCO2 and [HCO3-] values were 2.7 and 3.2 fold as high as the values of control fish. [Cl-] concentration in plasma of fish in 2% and 3% CO2 treatments were significantly decreased after 48 hrs. of CO2 exposure in comparison with control treatment (p2 concentrations (p