RESPONSES OF RED NILE TILAPIA (Oreochromis niloticus L.) SUBJECTED TO SOCIAL AND CONFINEMENT STRESSES
Keywords:Confinement stress, plasma cortisol, Red Nile tilapia, skin color, social stress, ventilation rate
AbstractRed tilapia is gaining popularity nowadays in the market but only limited studies on its behavioral and physiological response to stress are available. In this study, 27 red Nile tilapia (RNT) were subjected to confinement and social stresses. This experiment monitored their physiological (plasma cortisol) and morphological (ventilation rate [VR] and skin color) responses to stress. The plasma cortisol and VR of the fish before exposure to stressors were significantly lower compared to their values after the introduction of stressor. For fish subjected to social stress, there was also a significantly higher cortisol level and VR in the subordinate fish compared to those in the dominant fish. The skin color of red tilapia was also intensified when the fish was subjected to confinement and social stresses. Higher plasma cortisol levels, faster VRs, and darker skin color were exhibited more by fish subjected to social stress compared to fish subjected to confinement stress. There was also positive correlation between mean plasma cortisol concentration and mean VR (r=0.945; P˂0.05).