TAILIEUCHUNG - Research on the fitness between the mesh size and the length of threadfin bream (Nemipterus sp.) in stow net fishery

The study has used 4 different mesh sizes and mesh shapes in codends, catching 40 trial hauls in Nai lagoon to collect data. The fishing process has collected 2,041 individual threadfin bream (Nemipterus sp.) for analysis of fish weight and length, and using Wileman's method of assessing the selective ability to determine selective parameters for threadfin bream. | Journal of Fisheries science and Technology No. 4 - 2018 RESEARCH ON THE FITNESS BETWEEN THE MESH SIZE AND THE LENGTH OF THREADFIN BREAM (Nemipterus sp.) IN STOW NET FISHERY Nguyen Trong Luong¹, Vu Ke Nghiep¹ Received: ; Revised: ; Accepted: ABSTRACT The study has used 4 different mesh sizes and mesh shapes in codends, catching 40 trial hauls in Nai lagoon to collect data. The fishing process has collected 2,041 individual threadfin bream (Nemipterus sp.) for analysis of fish weight and length, and using Wileman's method of assessing the selective ability to determine selective parameters for threadfin bream. The research results show that the fish length with the probability of 50% retained in the codends (L50) of the samples M1, M2, M3 and M4 is respectively , , and . The selection factor (SF) of the diamond mesh is and the square mesh is . The appropriate the mesh size for fishing with L50 is 21mm for both diamnond mesh and square mesh. Key words: Nemipterus sp., stow net fishery, mesh size, fishing gear selectivity. I. INTRODUCTION For the stow net activity in Nai lagoon, Ninh Thuan province, the economic value and the yield of Nemipterus sp. are high. Among 14 common species, nemepterus account for of the total exploited species. However, the yield of this species tends to decline sharply, from tons (in 2012) to tons (in 2016), the average decreased by per year [4,5]. The stow net activitiy in Nai lagoon is not large, the number of households participating in this activity are small [6]. However, the stow net is fixed at Tri Thuy bridge area - is the circulation gate from Nai lagoon to Phan Rang bay, the mesh size at the codend is small, 2a = 12mm, the mesh size is diamond and made by nylon, therefore, under the effect of flow, meshes are deformed and closed, which reduces the the escape ability of the small fish [6]. Therefore, the stow net can catch all species flowing the water

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