A Basic Study on the Sinking Material Improvement for Offshore Small Yellow Croaker Drift Gill Net Fishing Gear

Abstract

This study is aimed to improve the sinker that is the sinking material of the offshore small yellow croaker drift gill net currently used in the field so that the sinker line of the net can float while maintaining a distance from marine wastes deposited on the seabed. Therefore, targeting the offshore small yellow croaker drift gill net equipped with the improved sinking material to prevent the damage or loss of the fishing gear, this researcher figured out the development characteristics of the attachment according to the improvement of the sinking material and carried out marine tests to analyze and investigate that. According to the results of the tests other than the fifth and sixth tests conducted according to water depth over time, in the range(0 ≤ R² ≤ 0.4), the FS and SFL seem to influence the changing water depth over time insufficiently. It would be okay to attach the floor line to the offshore small yellow croaker drift gill net because the way of development is not different from the previous one. When R² comes closer to 1, the change of water depth influences the FS and SFL of the offshore small yellow croaker drift gill net equipped with the floor line significantly. And when it comes closer to zero, the floor line influences the FS and SFL of the offshore small yellow croaker drill gill net insignificantly. Also, Nets are divided into the offshore small yellow croaker drift gill nets equipped with the floor line with the width of 200 and the offshore small yellow croaker drift gill nets with the width of 300 previously used to figure out the replacement of the nets. According to the findings, the offshore small yellow croaker drift gill nets equipped with the floor line indicate a very low replacement rate as 2.4% out of the total amount of the nets.