Assessment of water quality in catfish (Pangasianodon hypophthalmus) production systems in the Mekong Delta

Abstract

Water quality in striped catfish (Pangasianodon hypophthalmus) production systems in the Mekong Delta was investigated to assess the potential impacts of the culture activity on the environment. The study was conducted at three culture systems, so called systems 1, 2 and 3 selected from the catfish culture areas of An Giang, Can Tho and Hau Giang provinces. A total of 21 sites were selected from 10 farms of these three systems for sampling. In system 1, sampling was implemented at inlets, culture ponds and outlets, whereas in system 2 and 3 samples were only obtained from inlets and culture ponds. Sampling was conducted three times throughout the production period including beginning, middle and the end. Main water parameters taken for the assessment consisted of pH, DO, BOD, COD, turbidity, TAN, N-NO2-, N-NO3-, TSS, TN and TP. The results indicated that most of parameters were still in the acceptable ranges except TN and TP. Dissolved oxygen concentrations were constantly above 5 mg/L. The highest concentrations of BOD and COD recorded were 10.7 mg/L and 19.6 mg/L in system 1 and system 3, respectively. Mean concentrations of TSS were relatively low in all systems ranging from 21 to 84 mg/L. However, TN and TP concentrations were considerably high. Concentrations of TN and TP recorded outside the culture ponds were 3 and 10 times higher than the standard levels (3 mg/L and 0.1 mg/L for N and P, respectively). TN concentration varied with the sampling periods but accumulation of TP tended to increase steadily throughout the production period.