The purpose of this study is to find the light intensity which induced maximum gathering rate and to observe the variation of the gathering rate both in daytime and tat night by using Striped puffer, Fugu xanthopterus (Temminck et Schlegel). An experimental tank(360L$ imes$50W$ imes$55H cm) was set up in a dark room. An illumination system was attached to the end of one side of the tank to control horizontal light intensity. Eight artificial light sources were prepared by combination of three light bulbs (10W, 60W, 100W) and eight filters. During the experiment water depth was maintained 50 cm level in the tank. The tank was marked into six longitudinal sections each being 60cm long to observe the distribution of fish. The fish were acclimatized in dark condition for 50 minutes prior to the main experiment. Upon turning on the light, the number of fish in each section was counted 60 times every 30 seconds, and the gathering rate was obtained from the average number of fish in each section. The light intensity inducing maximum gathering rate was 298.56 lux (188.44-444.96 lux) at daytime and 298.56 lux (188.44-444.96 lux) at night. The variation of the gathering rate of fish in illumination time was increasing trend fluctuately and did not show any distinctive difference between day and night.