Journal of Zhejiang University SCIENCE
(ISSN 1009-3095, Monthly)

2005   Vol. 6B   No. 8   p.812-816

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

XU Jian-yu^†1,3, MIAO Xiang-wen¹, LIU Ying^†‡2, CUI Shao-rong¹

(¹Institute of Agricultural and Bio-Environmental Engineering, Zhejiang University, Hangzhou 310029, China)
(²Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China)
(³Faculty of Information Science and Technology, Ningbo University, Ningbo 315211, China)
^†E-mail: xujianyu@nbu.edu.cn; yinliu@ms.qdio.ac.cn
Received Mar. 30, 2005; revision accepted May 29, 2005

Abstract: 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.

Key words: Ammonia stress, Tilapia, Computer vision, Aquaculture
doi:10.1631/jzus.2005.B0812             CLC number: S126

^‡ Corresponding Author