Abstract
Utilizing the fact that the horse mackerel Trachurus japonicus, has an outstanding aversion for specific intermittent light, it has been elucidated through a series of experiments that the passage of a fish school can be blockaded or a fish school can be trapped into an enclosed site. In this investigation, the intermittent light was used as a beam, and a certain number of beams were projected at once.
Under adaptation to dark conditions, the passage of the fish school was completely suppressed when the ratio of light intensity between light beams and background was more than 83:1, and the space between the beams was less than 50 cm. However, under light adaptation, suppression of passage required a ratio of more than 60 times that needed under dark adaptation. It has additionally been confirmed that such a suppressional effect as discussed was sustained for more than 100 hours without necessitating any changes in conditions of intermittent light beams.
