Application of a real-time underwater surveillance camera in monitoring of fish assemblages on a shallow coral communities in a marine park

An underwater surveillance camera has been designed for monitoring fish species activity on an inshore coral reef in a Marine Park in Hong Kong. The system consisted of a high-resolution camera. It was connected to the shore base station via a fibre-optic cable with power conductors. The camera could record video on a DVD recorder with hard disk in real time. The system was designed to be used for long periods of time up to three months continuously without maintainence. It was used to monitor changes in coral fish abundance with respect to time of day and among months. The present results thus showed two major behavioural patterns of coral fish in Hoi Ha Wan. The first is the diurnal activities as most fish species are active during the daylight rather than at night. Both mean number of species and fish density showed an increase in daylight and a decrease at night. The second was the seasonal migratory pattern. A seasonal variation of fish abundance on a subtropical reef was recorded with water temperature changes from 29degC in summer to 17degC in winter. Mean maximum number of species during daylight in warmer months was _~10-12 while that in colder months decreased to 2-3.