Behavioral response of tilapia （Oreochromis niloticus） to acute ammonia stress monitored by computer vision

INTRODUCTION Fish behavior under culture conditions holds important information for aquaculturist (McFarlane et al., 2004; Kristiansen et al., 2004). Most physiological,environmental changes and handling process can in-duce variations in fish behavior (Israeli and Kimmel, 1996; Israeli-Weinstein and Kimmel, 1998; Petrell and Ang, 2001; Almazán-Rueda et al., 2004). Meth-ods of monitoring and quantifying the behavioral re-sponse have become potential alternatives for assess-ing stress…

Behavioral response of tilapia (Oreochromis niloticus) to acute ammonia stress monitored by computer vision

The behavioral responses of a tilapia (Oreochromis niloticus) school to low (0.13 mg/L), moderate (0.79 mg/L) and high (2.65 mg/L) levels of unionized ammonia (UIA) concentration were monitored using a computer vision system. The swimming activity and geometrical parameters such as location of the gravity center and distribution of the fish school were calculated continuously. These behavioral parameters of tilapia school responded sensitively to moderate and high UIA concentration. Under high UIA concentration the fish activity showed a significant increase (P＜0.05), exhibiting an avoidance reaction to high ammonia condition, and then decreased gradually. Under moderate and high UIA concentration the school's vertical location had significantly large fluctuation (P＜0.05) with the school moving up to the water surface then down to the bottom of the aquarium alternately and tending to crowd together. After several hours' exposure to high UIA level, the school finally stayed at the aquarium bottom. These observations indicate that alterations in fish behavior under acute stress can provide important information useful in predicting the stress.