Suggestion of the appropriate Mozambique purse seine fishing gear using numerical method

Abstract

Mozambique currently has no tuna purse seine fleet. Here, a tuna purse seine fishing gear is proposed to fit the Mozambique fishing ground. The numerical method was applied to evaluate the tuna purse seine fishing gear’s mechanical proprieties. The tuna purse seine gear layout was proposed based on the modification of the Iranian tuna purse seine fishery operating in the Indian Ocean. To do those modifications, it was compared to the Korean commercial purse seine gear which is larger and heavily rigged. The Korean gear sank at an average speed of 0.34 m/s and the Iranian with 0.28 m/s, and within 300 s both gears attained depths of 90 m and 121 m, respectively. After the simulations the Iranian gear was modified by increasing its length, depth (Design-I), to 986, 217 m, and sinker line weight 5.29kg/m (Design-II) in order to match that of the Korean tuna purse seines. The design and simulation were done using the SPurse and SimuPurse software developed by the Marine Production Systems Management and Laboratory (MPSL), Marine Production Systems and Management Division, Pukyong National University, Busan, South Korea. The results showed that the leadline sinking depths of the two Designs (Design-I and Design-II) purse seines were 96 and 105 m, respectively and their average sinking speeds were 0.287 and 0.289 m/s. The tension on their purse lines were 5,230 and 6,216 kgf. The PA knotted netting was changed to PES knotless (Design-III) netting and showed a greater effect on the sinking performance. Comparing the sinking performance of the leadlines and considering that in the Indian Ocean, particularly in Mozambique Channel, the tuna and tuna-like species are caught near logs and FADs, the designed tuna purse seine gears fit well in this type of fishery.