Effects of Ammonia on the Growth, Survival and Quality of Tra Catfish (Pangasianodon hypophthalmus)

Tra catfish (Pangasianodon hypophthalmus) is one of the most valuable freshwater species and is popularly farmed in Vietnam. Tra catfish is mainly consumed by exporting to different countries in the world; thus, it is necessary to meet the criteria for flesh quality of the imported countries. Therefore, the present study aimed to minimize the concentration of NH3 in striped-catfish cultured ponds to improve the flesh quality of Tra catfish. The study comprised two experiments: (1) determination of the lethal concentration (LC) of NH3 on Tra catfish and (2) investigation of the effects of NH3 at concentrations (control, safety, LC10, and LC20) on the growth, survival and flesh quality of Tra catfish. These experiments were set up following a completely randomized design with 3 replications in 500 L tanks. The size of Tra catfish was about 55 ± 5.8 g/fish. The temperature and pH were controled at 28oC ± 0.2 and 8.0 ± 0.3, respectively. The results showed that, the safe concentration, LC10 and LC20-96 h of NH3 on Tra catfish was 0.2, 3.61, and 3.73 mg/L, respectively. The specific growth rates (SGR) of fish at safe concentration (0.18%/day), LC10 (0.12%/day) and LC20 (0.088%/day) were significantly lower than that in control (0.56%/day). The survival rates of fish at LC10 (86.7%) and LC20 (71.7%) of ammonia were decreased significantly compared with control and safe concentration (96.7%). The sensory evaluation found that, the treatments at the safe concentration, LC10 and LC20) were affected the flesh quality of the fish. The control with 19.11/20 scores was the best result, while other treatments were at moderately good levels (15.2 – 18.5/20 scores).