Description and evaluation of a photoelectric system for monitoring the locomotor activity of a pelagic fish

Abstract

A photoelectric system, designed to monitor continuously the 'spontaneous' locomotor activity of individual, juvenile pink salmon in the laboratory, is described and evaluated quantitatively. Data on the swimming behaviour of individual fish in the circular channel indicate that the design permitted salmon to swim freely in circuits without physical obstructions impeding or water currents directing their movements. Swimming speeds of individual fish were not influenced by infrared light beams emitted across the activity channel. The photoelectric monitoring system was found to be reliable, equally sensitive in detecting the locomotor movements of small (4.3–5.8 cm) and of large (13.0–19.0 cm) fish, and provided data which closely approximated (on average to within 94.0–102.6%) the total momentary locomotor activity of individual pink salmon.