Fish school monitoring technology is utilized for various purposes, such as boat fishing and resource surveys. With advancements in information and communication technology, this technology has expanded its application to remote areas. Its significance has grown in fishing sites, particularly for improving the efficiency and cost-effectiveness of set-net fishing. Set-net fishing gears are not limited to coastal areas, but are also installed in inland and remote sea regions. Consequently, fishermen require technology that allows them to quickly transmit information about approaching fish schools and enables them to perform long-term monitoring. The development of remote monitoring technology for set-net fish schools must consider crucial design factors such as communication range, transmission speed, power consumption of information modules, and operational expenses. In this study, we developed a low-power remote monitoring module for set-net fish school based on WCDMA. The module was specifically designed to minimize power consumption, allowing for communication over long distances and extended operation times in set-net fishing applications. Furthermore, we developed a web server software application that enables remote access to fish schools and provides real-time weather information. The performance of the developed module was evaluated through set-net fishing site application and experiments with moving ships on the sea. The experimental results demonstrated that the remote monitoring system, consisting of the developed low-power remote monitoring module for set-net fish school based on WCDMA and a fish finder, had an average power consumption of 4.6 W, a maximum communication range of 22.84 km, and a data transmission and reception rate of 98.79%. The maximum fish school information transmission and reception rate was 97.26%.

This study analyzed the duct characteristics of hubless rim-driven propeller (RDP) used in underwater robots. In the previous study, flow visualization experiments were performed with an advancing ratio of 0.2 to 1. The vortex at the front of the duct increased in strength while maintaining its size as the advancing ratio decreased. Therefore, it is necessary to study the optimization of the duct shape. Conventional propeller thrusters use acceleration/deceleration ducts to increase their efficiency. However, unlike conventional propellers, it is impossible to apply to airfoil acceleration/deceleration ducts due to the RDP structure. In this study, duct wake flow characteristics, thrust force, and efficiency according to the duct shape of RDP were analyzed using numerical analysis techniques. Duct design is limited and six duct shapes were designed. As a result, an optimized duct shape was designed considering duct wake flow characteristics, thrust force, and efficiency. The shape that the outlet width of the RDP was kept constant until the end of the duct showed higher thrust force and efficiency.

The concern on the greenhouse gas emissions is increasing globally. Especially, the greenhouse gas emission from fisheries is an important issue from the Paris Climate Change Accord in 2015. Furthermore, the Korean government has a plan to reduce the GHG emissions as 4.8% compared to the BAU in fisheries until 2020. However, the investigation on the GHG emissions from Korean fisheries rarely carried out consistently. Therefore, the quantitative analysis of GHG emissions from Korean fishery industry is necessary as a first step to find a relevant way to reduce GHG emissions from fisheries. The purpose of this research is to investigate which degree of GHG emitted from the major offshore fisheries such as offshore gillnet fishery, offshore longline fishery, offshore jigging fishery and anchovy drag net fishery. Here, we calculated the GHG emissions from the fisheries using the Life Cycle Assessment method. The system boundary and input parameters for each process level are defined for the LCA analysis. The fuel use coefficients of the fisheries are also calculated according to the fuel type. The GHG emissions from sea activities by the fisheries will be dealt with. Furthermore, the GHG emissions for the unit weight of fishes are calculated with consideration to the different consuming areas as well. The results will be helpful to understand the circumstances of GHG emissions from Korean fisheries

The objective of this study was to estimate physical properties and fishing performances of net twine with improved PBS copolymer resin (Bio-new), the existing PBS/PBAT blending resin (Bio-old) and commercial Nylon (Nylon). The tensile strength of Bio-new monofilament was equal to Bio-old and the elongation of Bio-new was about 6 % higher than that of Bio-old in wet condition. The physical properties tests were carried out to estimate breaking load and stiffness in dry and wet conditions, respectively. In the results, the breaking load of Nylon netting was the highest whereas the elongation of Bio-new was 1.4 times higher than that of Nylon netting in wet condition. The breaking load of Bio-old netting was about 9.2 % higher than that of Bio-new netting. However, the elongation of the Bio-new netting was about 3% higher than that of Bio-old. The stiffness of the Bio-new compared to Bio-old was improved about 34 % in dry condition and about 32 % in wet condition. The filed experiments of the fishing performance were conducted with three kinds of drift nets with different netting materials in the coastal sea of Jeju. The each experimental drift net made of different materials showed the similar fishing performance. Bio-old drift net yielded less catches of small sized yellow croaker than other drift nets. The netting materials affected the fishing performance and length distribution of catches in the drift nets.

Comparative fishing experiments were conducted in the eastern coastal waters near Uljin, Korea from 2002 to 2004, using the experimental trammel nets to estimate the selectivity for spinyhead sculpin Dasycottus setiger. The inner panels of the nets were made of nylon monofilament with four mesh sizes (82.2, 89.4, 104.8, and 120.2 mm) while its two outer panels were made of twisted nylon multifilament with a mesh size of 510 mm. The SELECT (Share Each Length’s Catch Total) procedure with maximum likelihood method was applied to obtain a master selection curve. The different functional models (normal, lognormal, bi-normal, and logistic model) were fitted to the catch data. The lognormal model with the fixed relative fishing intensity was chosen as the best-fitted selection curve through comparison of model deviance and AIC (Akaike’s Information Criterion). The optimum relative length (the ratio of fish total length to mesh size) with the maximum relative efficiency was obtained as 2.492.

Fishing pots are one of the important fishing gears in our coastal and offshore fisheries. In terms of a sustainable use of marine resources, there are concerns about the ghost fishing by lost pots. It is reported that 10 to 70% of the pots are abandoned or lost annually. This study is to compare the catching efficiency of drum type whelk pots that are made of biodegradable nets to those made of the ordinary nets, in the eastern coast of Korea. Five types of drum pots were used with combination of biodegradable nets and ordinary (PA, PE) nets applied to the main and funnel parts of the pots: pots with biodegradable nets (Bio+Bio); pots with PE net (PE+PE); pots with body and funnel made of biodegradable nets and PE nets respectively (Bio+PE); pots with body and funnel made of PE nets and PA nets respectively (PE+PA); pots with body and funnel made of PE nets and biodegradable net respectively (PE+Bio). Field experiments were conducted from June 18th, 2015 to August 7th, 2015 using a commercial fishing vessel in the Uljin waters on the eastern coast of Korea. Two fleets of pots with one hundred in each, 20 pots of each type, were casted for 8 to 15 days to analyze their catching efficiency. The catch of target species, whelks, was 202,563.0 g with catch rate of 38.7% of the total catch, while the bycatch was 320,709.7 g with the rate of 61.3% of the total catch. The catch of whelks was the highest in the Bio+PE pots (46,020.3 g), followed by the Bio+Bio pots (42,027.5 g), the PE+Bio pots (41,849.9 g) and the lowest being PE+PE pots (38,054.2 g). Compared to the conventional pots, the pots with biodegradable nets on the body or entrance part had slightly higher catch rate for both the target species and the bycatch. The PE+PE had the lowest catch rate. There is no significant difference in catch between the pots with biodegradable nets and the ordinary nets for the target species such as Buccinum opisthoplectum, Neptunea eulimata, Buccinum striatissimum. Consequently, using biodegradable nets for the conventional whelk pots can reduce ghost fishing by lost gears while keeping the performance of the pots.

Spinyhead sculpin Dasycottus setiger, a species of cold water fish, is distributed along the eastern coastal waters of Korea. A series of fishing experiments was carried out in the waters near Uljin from June, 2002 to November, 2004, using the experimental monofilament gill nets of different mesh sizes (82.2, 89.4, 104.8, and 120.2 ㎜) to describe the selectivity of the gill net for the fish. The SELECT (Share Each Length’s Catch Total) analysis with maximum likelihood method was applied to fit the different functional models (normal, lognormal, and bi-normal models) for selection curves to the catch data. The bi-normal model with the fixed relative fishing intensity was selected as the best-fit selection curve by AIC (Akaike’s Information Criterion) comparison. For the best-fit selection curve, the optimum relative length (the ratio of fish total length to mesh size) with the maximum efficiency and the selection range (R50%,large - R50%, small) of 50% retention were obtained as 2.363 and 0.851, respectively. The ratios of body girth to mesh perimeter at 100% retention where the selection curve of each mesh size represented the optimum total length were calculated as the range of 0.86 ~ 0.87.