Stress responses of red tilapia (Oreochromis spp.) to high ammonia levels

Red tilapia is becoming a popular species in aquaculture but few studies are available regarding its responses to environmental stress. In this study, 16 pieces of Red tilapia was subjected to high ammonia levels. Stress level was monitored by means of observing the changes in ventilation rate (VR), eye color pattern (ECP) and skin color of the fish before the introduction of stressor and immediately after 2, 4, 6, 8, 10 and 30 min later. Three treatments were assessed: T1 (control); T2 (0.046-0.05 ppm of NH3-N); T3 (0.06-0.10 ppm of NH3-N) and T4 (0.11-0.15 ppm of NH3-N). Results showed that the mean VR, ECP and skin color of the Red tilapia exposed to ammonia stress (T2, T3 and T4) were significantly higher (P<0.05) compared to control (T1). Faster VR, darker ECP and intensified skin color were observed in all treatments with high ammonia levels.