駆集網に関する二つの実験方法による網目の大きさ

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概要

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• The author conducted fundamental experiments on the effects and principles of fishing methods and gears. Those experiments were carried out by observing the locomotion activity of fish individuals kept in a tank, set for this purpose. The locomotion activity would differ according to the influence created by the environmental condition or model of fishing gear used. The experiments were done with 10 Goldfish Carassius auratus of an average total length of 4.0cm. They were liberated in a wooden tank of 150cm. long, 26cm. wide and 8cm. water depth. For model nets, 8 wooden frames were made and fine cotton thread was stretched vertically on each frame at intervals of 0.75, 1.00, 1.25, 1.50, 2.0, 3.0, 4.0cm except the 8th one which was wooden frame without thread as a contrast. Two methods, namely, "Centralizing method" and "Driving to one side method" were applied here. (Fig. 1 and 2) The first method is to drive fishes towards the center of tank from either side with two frames of different meshes, each at a driving speed of about 10cm. per minute. (Fig. 1) The number of fish which passed through each frame were counted. This was repeated for twenty times, using the same combination of frames. The total number of fish passed through the frame to either side was then found out. The same procedure was repeated using all these 8 frames, and in all combinations of two frames, each. The sum of the total values are given in Table 1. For the ratios of the number of passage of fish to either side of tank, the chi-spuare test of statistics was applied and the result is expressed in Table 1 as percentages of degrees which differ significantly. The second method is to drive fishes to one side of tank from the other side by one frame with a speed of 10cm. per minute as the former. (Fig. 2) When the fishes are driven up to a certain position, the fishes start to turn back and locomote to the other side passing through the frame. The position of the frame from one end of the tank was observed (Fig. 2, d), and the result of 40 such experiments are given in Table 2 and Fig. 3, and the efficiency of driving is given in Table 3. The numerical values, so far got, were converted into common logarithm to get their mean values and to compare them. (Table 4) It has been found that a significant difference exists in almost all combinations when examined by the F-table of statistics. (Table 5) Consequently, the centralizing method is so reliable as to compare directly the difference between two testings and the driving to one side method is advantageous to express sharply the peculiar quality of each testing.

• 社団法人 日本水産学会の論文

著者

• 草下 孝也

  東京大学農学部

関連論文

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• 傾斜沈垣網の効果について
• 彩色した沈垣網の効果について
• 狭い場所から開放されたときの魚群の行動
• 魚の種類による駆集網の駆集効果
• 駆集網に関する二つの実験方法による網目の大きさ
• 駆集網の色彩の濃さの効果について

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