Real-time monitoring of fish activity on an inshore coral reef

This paper describes an underwater camera and instrumentation system for monitoring fish species activity on an inshore coral reef in a Marine Park in Hong Kong. The system consists of a high-resolution pan, tilt and zoom camera with associated instrumentation package for measuring the local environment, including dissolved oxygen, temperature, pressure, salinity and ambient light conditions. It is connected to the shore base station via a fibre-optic cable with power conductors. The system is designed to be used for long periods of time, continuously. The first period chosen was for 100 days during the coral spawning season from June to August 2004. The system has also been used regularly for 2-3 weeks at a time to monitor changes in fish behaviour in different climatic conditions. Results from the initial experiment show that fish species activity is generally markedly different from that recorded by human divers. There is also some correlation between species, time of day, and climatic and environmental conditions - correlations that have not been reported before. The paper will give details of the results of the observations, as well as technical details of the system. It will also refer to an associated project using an ROV for transect measurements on the reef, data from which has a bearing on the subject of the paper.