燈火に集まる魚群に就て第1報
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概要
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We had an experiment done off Naruto of Awaji Island of Hyogo prefecture in summer 1949, by means of the Matuda fishing electric lamp and a purse seine. In most cases of practicess, the shoal is composed of “Katakutiiwasi” Engraulis japonicus (T. &. S.) and “Maaji” Trach ?? rus 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 the boardside, we measure the visible depth of Secchi disk placed vertically beneath the source. After a few hours, fishes 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 southeasterlcurrent is unfavourable 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 limitis same to the lamp). but in the case of “Maaji” only, the upper limit of the shoal is same to the depth of 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 “Katakuti-iwasi”, if the depth of the lower limit of the crowding vertically under the source and the number of fishes composing the shoal are expressed by d and v respectively, v∞d1.5.