A study on a fish school's reaction in response to the change of physical environments. III. Response of a fish school to different wavelengths of intermittent lights and different background irradiances under projected light.

Abstract

Variations in degrees of fish's aversion to intermittent light in response to different wavelengths of lights and different background irradiances under projected light were studied from an ecological point of view in this report. A school of one-year-old Japanese horse mackerel Trachurus japonicus soon after being caught, were used for the experiments. As a result, it is clarified that the fish school shows higher degree of aversion to blue intermittent light than that to red intermittent light; that, notwithstanding that the underwater energy of the blue intermittent light is only 1/6 that of the white intermittent light, both lights have almost no difference in degrees of fish's aversion. Furthermore, it is revealed that, when the intermittent light of 100lx is projected, the most prominent degree of aversion to light is seen when background irradiance is less than 0.003lx, and it decreases with increasing background irradiance but a certain degree of aversion still remains up to irradiance of 0.02lx and then, it disappears completely when irradiance reaches to 0.2lx.