Flume tank and in situ trials for verification of static and dynamic methods for gear depth and underwater behavior of hairtail trolling lines |
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Authors: | Gebremeskel Eshetu Kebede Chun Woo Lee Subong Park Mun Kwan Kim |
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Affiliation: | 1.Department of Fisheries Physics, Division of Marine Production System Management, College of Fisheries,Pukyoung National University,Busan,Korea;2.Ocean and Fish Res Institute,Jeju,Korea |
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Abstract: | We investigated the underwater shapes of trolling lines for the improvement of hairtail fishing efficiency. Two sets of experiments were carried out, one on a small scale, where flume tank tests of four models were scaled down by a ratio of 1:10 and trolled at different speeds, and another at full scale, comprising a survey on board a commercial fleet. In situ trials were conducted off the coast of Jeju Island, South Korea, at 33°27′57.528″N, 126°55′48.846″E, a potential fishing ground for hairtail fishing. The full-scale gear was set by altering sinker weights whilst changing the length of the warp line at different towing speeds. A dynamic method using a mass-spring technique and full-scale gear was developed. External and internal forces that govern the motion of the gear were considered. A non-linear differential equation of motion was developed, solved by a fourth-order Runge–Kutta method at a time step of 5?×?10?4 s for each trial. A static method was also developed using full-scale gear to predict the equilibrium gear configuration under all fishing conditions. The dynamic method better predicts the actual underwater performance of trolling line gear in real time. |
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