In order to clarify the form of a sergestid shrimp under operation, field measurements of net and fishing conditions were made on a commercial fishing boat. It was found that the height of the net mouth decreased with increase in the towing speed and there were complex behaviors as to the hieght of the net mouth corresponding with the warp length and the distance between the boats uncer operation. The average height of the net mouth is 27m in the spring, and 38m in the autumn fishing seasons. The orientation of the net mouth during operation is slightly upwards. The relationship between the depth of the net and the warp length was also obtained; the longer the warp is, the greater the depth of the net. Since the depth of the net center is 66% of the warp length, the necessary length of warp under operation is as much as 1.5 times the depth of the center of the patch of shrimps. However, the relationships between the depth of the net and the towing speed, and between the net depth and the distance between the boats are not so clear.