The object of the study was to clarify from an ecological point of view that such an inconstant lighting condition which goes on and off with a short cyclic time as the intermittent or flickering light would give a different stimulation from that of a constant light to fish. Horse-mackerel Trachuras japonicus were used soon after being caught by a stationary trap net for a series of experiments, and the observation of the fish school's behavior was continuously carried on for a period of 90 days, during which experimental fish were replaced with new ones everyday. Thus, the total number of fish used for the study amounted to 1, 200.
As a result, it has been confirmed that not only is there a remarkable difference between fish-school behavior in response to inconstant light and that to constant light, but also their behavior varies in great deal with the blinking frequency of the inconstant light.
