## 1 Introduction  
Recently, marine-environmental pollution caused by marine litter has increased. In particular, the marine-environmental pollution caused by the loss of fishing gear is recognized as a serious problem [1]. In South Korea, 20% of used fishing gears are lost or abandoned, and only approximately 15% of the lost or abandoned fishing gears are collected--therefore, the remaining 85% may harm the marine ecosystem [2]. To prevent the loss of fishing gear, it is necessary to better understand the dynamics and behaviors in waves and currents, and develop an efficient way to monitor them.  
The predominant type of fishing gear in South Korea is the drift gill net, stow net, and fish trap. Among them, the stow net has traditionally been utilized on the southwest coast of South Korea by using strong tidal current [3; 4]. The stow net freely changes its direction according to the direction of current flow by a single-point-mooring line (SPM) fixed with anchor, and the current force leads to the catch of fish. In order to realize such characteristics, the density of its net entrance should be smaller than that of water. As the stow net influenced by strong current and wave excitations, the possibility of net-loss increases a lot through braking of lines or twisting of net assembly.  
In this regard, reliable numerical tools for the global-performance evaluation of stow nets for diverse ocean environmental conditions are needed. Cage-mooring-coupled-dynamics numerical tools have been developed by several researchers using the Morison-force and screen models. Whenthe inflow angle is less than 45\({}^{\circ}\), the Morison-force model provided good validation results against measurements even without considering interactions between twines [5]. [PERSON], et al. [6] suggested a mathematical model to analyze fishing cage system in current and wave including comparisons with experimental results. [PERSON], et al. [7] investigated the effects of waves and currents on gravity-type cages and mainly focused on mooring tensions and volume reduction coefficients of the cage. In addition, [PERSON] and [PERSON] [8] conducted a fatigue analysis of a SPM-cage system under wave and current loads. [PERSON], et al. [9] investigated hydrodynamic behaviors of gravity cages in currents and waves including comparisons with experimental results. [PERSON], et al. [10] studied dynamic behaviors of box and column-shaped net cages in waves and currents. [PERSON] and [PERSON] [11] conducted numerical simulations of a fishing net in currents, and a wake model was applied to downstream nets. In addition, [PERSON] and [PERSON] [12] further investigated dynamic behaviors of fishing nets under wave and current excitations. [PERSON] and [PERSON] [13] also investigated the coupled dynamics of a complex system including SPM-buoy-feeder-cage. [PERSON] and [PERSON] [14] also solved hydrodynamic responses of a floater-net system in currents and waves.  
The purpose of this study is to predict dynamic behaviors of stow nets for various ocean conditions by using time-domain computer simulations and assess the feasibility of the corresponding monitoring system. Sensors can measure buoy motions and mooring/rope tensions. Traditionally, the performance analysis of stow nets was checked by test operations or small-scale experiments [15; 16; 17; 18; 19; 20]. Through numerical simulations, more physical insights for better design and operation are available. Furthermore, with the accumulated data by numerical simulations, it can indirectly be used for checking net performance.