Mesh Size Selectivity of Tie-Down Gillnets for the Blackfin Flounder (Glyptocephalus stelleri) in Korea

Pyungkwan Kim,Hyungseok Kim,Seonghun Kim

doi:10.3390/app11219810

Pyungkwan Kim, Hyungseok Kim + Show 1 more

Open Access

https://doi.org/10.3390/app11219810

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Abstract

Although gillnet fisheries are increasingly common in Korea, few studies have conducted sea trials using tie-down gillnets. Here, we analyzed the mesh size selectivity using tie-down gillnets with four different mesh sizes (84, 90, 105, and 120 mm) to catch blackfin flounders. A total of 10 sea trials were conducted at depths of 100–140 m in the waters of Yangyang County, Gangwon Province, Korea, and the catching efficiency and mesh size selectivity were comparatively analyzed. The net with a mesh size of 84 mm showed the highest number of catches (373), followed by the 90-mm (363) and 105-mm (307) meshes. The results of the master curve estimation showed that the larger the mesh size, the higher the total length representing the same retention probability. Therefore, the catch rate of small fish decreased with the increasing mesh size. For the 84-mm net, the 50% selection length for small fish (total length ≤ 170 mm) was estimated at 186.9 mm, which was approximately 17 mm larger than the length limit. The results show that when using tie-down gillnets, the size of the fish caught changed according to the changes in the mesh size.

Highlights

A gillnet is a type of fishing gear typically composed of a rectangular net with a float at the top and a sinker at the bottom that allow the net to extend vertically in water
The experimental gillnets used to conduct the sea trials were based on the blackfin flounder tie-down gillnets used in the waters off Gangwon Province and had the same area and composition
In the master curve for mesh selectivity, the optimal length/mesh size (l/m) value with a retention probability of 1 was 2.70, and the 50% selection range was 2.225–3.116 with an interval of 0.891. This suggests that with the increasing mesh size, the fish with longer total lengths exhibited the same retention probability. This confirmed that the catch rate of small fish decreased with an increase in the mesh size

Summary

Introduction

A gillnet is a type of fishing gear typically composed of a rectangular net with a float at the top and a sinker at the bottom that allow the net to extend vertically in water. The gillnets are placed in a certain water depth at locations where fish encounter the net and are trapped such that the gills or other parts of the body are held by the mesh size. Gillnets are generally used in research to estimate the abundance, ecological properties, catchability, diversity of species, diet of species, growth, maturity of the target species, and age structures of fish populations. Gillnets are one of the highly size selective gears in commercial fisheries [1,2,3,4,5]. In terms of research gear, different mesh sizes have been used simultaneously to observe the size frequencies for the effects of mesh size selectivity, ecological parameters, relative fishing efficiency, and conservational feasibility for sustainable utilization [6,7,8,9,10]

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