On the shoal of fishes crowding toward a lamp (1)

We had an experiment dome off Naruto of Awajii Island of Hyogo prefecture in summer 1949, by means of the Matuda fishing electric lamp and a purse seine. In most cases of practices, the shoal is compose of "Katakutiiwasi" Engraulis japonicus (T. S.) and "Maaji" Trachurus japonicus (T. S.). Prior to starting this experiment, we measure the illumination in several directions by means of the Matuda lux meter and determine the vertical distribution curve of the source. Hanging down the source attaching on board side, we measure the visible depth of Secchi disk placed vertically beneath the source. After a few hours, fished densely crowded, we measure vertically and horizontally the range of the crowding and then the pursing is completed. From these measurements, the following data is obtained. 1. Tiding, must be in strict connection with the shoal crowding, especially the course of southeastern current is unfavorable for the number of the shoal toward the lamp. 2. comparing the shoal in the cases of "Katakutiiwasi" with that of "Maaji", we know that the depth of the upper limit of "Maaji" is lower than that of "Katakutiiwasi" (the depth of the upper limit is same to the lamp). 3. The depth of the upper limit of the shoal of Katakutiiwasi in the moon light is lower than that in the dark. 4. In the case of "Katakutiiwasi", if the depth of the lower limit of the crowding vertically under of fishes composing the shoal are expressed by d and v respectively, v*d[super]1.5.