Improvement of the sinking performance of the Vietnamese tuna purse seine

Abstract

In this study, numerical method was used to assess mechanical properties and improve Vietnamese tuna purse seine. The data were extracted from the two projects of national level. The simulation process was implemented on simulation software, SimuPurse, developed by Marine Production System Laboratory, Marine Production Management Division, Pukyong National University, Busan, Korea. The study results showed that, there was a very low sinking performance of Vietnamese tuna purse seines. Average lead-line sinking speed reached 0.139 m/s and 0.143 m/s for the gears 2003 and 2014 respectively. The maximum sinking depths of lead-line reached 61.6 m (The gear 2003) and 65.8 m (The gear 2014). Sinking performance of the gear 2014 was higher than of the gear 2003. The maximum tension magnitudes on ring line of Vietnamese tuna purse seine 2003 was 4742kgf and 2014 was 4219kgf (in term of current speed of 0.11 m/s, 0.34 m/s, 0.29 m/s with heading of 180o, 210o, 250o for three layers and pursing speed of 1.7 m/s). The improved tuna purse seines I, III and IV showed similar sinking performance results with 0.22 m/s, 0.219 m/s and 0.219 m/s respectively. The average lead-line speed of improved gear II was lowest with 0.215 m/s. The maximum lead-line sinking depth of four improved gears I, II, III and IV were 116 m, 112 m, 115 m and 114.9 m respectively. Maximum tension magnitudes on ring line of the improved gears I, II, III and IV were 5657kgf, 5406kgf, 5645kgf and 5654kgf respectively. The sinking performance of improved tuna purse seines was higher, and small tension on its ring line corresponds with the current tuna purse seiners in Vietnam. The improved tuna purse seine IV is the most suitable for Vietnamese tuna purse seine fishery, it corresponds with tuna purse seiner scale and its fishing supporting equipment at the present.