Monitoring the behavior of hypoxia-stressed Carassius auratus using computer vision

Behavioral variations of a school of fish (Carrasius auratus) in a tank were monitored using computerized vision while the fish were subjected to hypoxia stress conditions. Two video cameras viewed the tank, one from the side through a transparent wall and one from above. The images were processed by a PC-based image processing algorithm which provided three coordinates of the school's center of gravity, with the standard deviations of each coordinate, and the projected spatial distribution of the fish. Stressed fish differed from controls with the following behavioral responses: (i) the center of gravity moved upwards and horizontally away from the transparent wall; (ii) swimming speed was apparently reduced; (iii) there were strong fluctuations in all three directions associated with spreading and contracting of the school; (iv) the periodic amplitude of the motion in the vertical direction increased. This study might evolve into an automatic stress warning technique for fish farms, based on alterations in the behavior of fish when stressed.