참치선망어선의 타원형 투망궤적 분석

Abstract

Tuna purse seine fishery, which is used to catch high-priced Skipjack tuna and yellow-fin tuna, has become one of the most popular fishing methods. Reflecting this trend, the number of tuna purse seiners registered with the Western and Central Pacific Fisheries Commission (WCPFC) recently doubled from 119 in 1988 to 251. Currently, Korea has about 50 tuna purse seiners, including local joint venture vessels. With the increase in the number of ships and advances in fishing techniques, the tuna purse seine fishery has resulted in a large amount of fish catch. Moreover, the use of fish aggregating devices (FAD; Payao) is blamed for the bycatch of juvenile yellow-fin tuna and bigeye tuna resources. Therefore, many international fisheries organizations are tightening regulations on the use of FADs to catch associated fish schools. In addition, it is becoming difficult to obtain fishing permits from countries with fishing areas. Therefore, a major challenge in tuna fishing is how to improve the catch of free swimming schools (unassociated schools) of fish that feed freely or migrate as compared to the associated school. However, catching unassociated fish schools requires a high level of skill and experience. In a previous study, to address this, a shooting trajectory assuming that the purse seine shooting trajectory is a circle was proposed based on the speed and direction of the movement of the fish school. However, in practice, a trajectory that is closer to an elliptical shape than a circular one is often formed. In this study, the existing circular trajectory and the elliptical trajectory methods were compared under the same conditions to confirm the effectiveness of elliptical shooting trajectory. In addition, changes in the eccentricity of ellipses were derived to assess which type of ellipse was appropriate as a shooting trajectory.