• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.171-178
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• 2015

Selectivity and by-catch are the main features used to define fish catch for fisheries management or to determine fishing gear efficiency. A fish girth distribution analysis was carried out to determine the retention rate of juveniles discarded and to establish common selectivity for a multispecies catch. Total body length, body weight, and girth of juvenile fish retained in the cod-end and cover net separately were collected using an 18-mm mesh cover net during 12 fishing trials with a 41-mm cod-end beam trawl. The by-catch weight ratio in the cod-end was twice that of the by-catch ratio in number. The 50% selectivity of body length and 50% girth of redfin velvet fish were not significantly different between the cod-end and cover net, whereas those of other fish species were significantly different between the cod-end and cover net. The difference in 50% selectivity girth of other fish between the cod-end and cover net was similar between cod-end mesh size and cover net mesh size. Furthermore, the difference in 50% body length selectivity of other fish between the cod-end and cover net was almost double the difference in girth. Girth selectivity in a multispecies catch using towed fishing gear was effectively used to determine fish and net mesh size.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.535-541
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• 2019

The purpose of this study was to investigate the possibility of fishery in offshore wind farms and evaluate the risk linked to the presence of turbines and submarine cables in these areas. With this objective, we studied an offshore wind farm in the Southwest Sea and the current state of vessels in the surrounding National Fishing Port. The risk assessment criteria for 22 fishing gears and methods were set by referring to the fishing boats; thereafter, the risk was assessed by experts. The fishing gears and methods that could be safely operated (i.e., associated with low risk) in the offshore wind farm were: single-line fishing, jigging, and the anchovy lift net. The risk was normal so that it is possible to operate, but the fishing gears and methods that need attention are: the set long line, drifting long line, troll line, squid rip hook, octopus pot, webfoot octopus pot, coastal fish pot, stow net on stake, winged stow net, stationary gill net, and drift gill net. Moreover, the fishing gears and methods difficult to operate in the of shore wind farm (i.e., associated with high risk) were: the dredge, beam trawl, and purse seine. Finally, those associated with very high risk and that should not be allowed in offshore wind farms were: the stow net, anchovy drag net, otter trawl, Danish seine, and bottom pair trawl.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.3
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• pp.218-226
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• 2013

The objective of this study is to estimate the optimal net twine thickness of drift net for yellow croaker. The filed experiments of the fishing performance were conducted with three kinds of drift net with different monofilament diameters (No.3=0.284mm, No.4=0.330mm, No.5=0.370mm) the total eight times in the southwest coastal sea of Korea. And the physical properties tests on the monofilaments of experimental net were carried out to estimated breaking load and softness in dry and wet conditions, respectively. From the results, the No.3 mono. was the strongest break load per unit area in dry and wet conditions. And the softness showed that the No. 3 mono. was the most soft than another experimental monofilaments. The fishing performance was; the No. 3 drift net showed the most catches. Conversely, the catches of No. 4 and No. 5 drift net showed the half on the catches of No. 3 drift net. Consequently, the diameter of monofilament in the drift net for yellow croaker should carefully choose to consider the economic sides such as the amount of catches and the cost of catches.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.279-286
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• 2018

The objective of this study was to quantitatively evaluate the influence of the netting hanging ratio on fishing performance of gillnet. A total of six tests was carried out using three kinds of gillnets with different horizontal hanging ratios (0.3, 0.5 and 0.7) on the basis commercial gillnet of mesh size of 60 mm used in Yeosu Dolsan. As a result of the test fishing operation, catches of the net with hanging ratio 0.3 and the shortest float length was 1.34 times larger than the net with hanging ratio 0.7. The caught species in experimental testes was lager in the net with hanging ratio 0.3 than the net with hanging ratio 0.7. The catch rate per unit area (CPUE) is on the silver croaker with the largest catches in tests as follows. The net with hanging ratio 0.3 net was $89.45g/m^2$, hanging ratio 0.5 net was $41.63g/m^2$, and hanging ratio 0.7 net was $24.50g/m^2$. The net with hanging ratio 0.3 (float line length of 45 m) exhibited the largest CPUE value.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.3
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• pp.214-222
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• 2022

This study calculated the on-site measurement (Tier 4) of greenhouse gases emitted during the production stage of major fishing periods that utilize set nets and bamboo weir fishing boats. In addition, using theoretically calculated results (Tier 1), the emission factor presented by the Intergovernmental Panel on Climate Change (IPCC) was comparatively analyzed. On average, carbon emissions for each operating period in the bamboo weir and set net were calculated to be 0.16 and 3.58 kg CO₂ time^-1, respectively; and the measurement values (Tier 4) for each tool were about 4-17 times lower than their respective theoretical values (Tier 1). Significant differences were found based on engine performance. As port entry, port departure, and operating periods of the vessels show negligible variation with short distances, the operation of the vessel engine was considered as the main variable for carbon emissions in anchovy set net fishing.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.326-336
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• 2003

In order to modify the construction of gizzard shad coastal purse seine net with possible to the laborsaving of fishing operation in the coastal small fishing vessels, the model experiments were carried out on the model nets for several conventional nets using in the field and the experimental nets was manufactured as 1/100 and 1/60 of the full scale net. The results obtained are summarized as follows；1. In the case of the conventional net and reduction rate 75% in conventional net with purse line the fishing efficiency decreased, the lead line was upward for the surface and the pursing depth of pursing line was very shallow to 2∼3m. 2. In the case of the net having maximum depth in center part designed in this study, the length of float and lead line was 60% of conventional net, the depth of net was fixed 20m to selvage line of the both of the end and extend gradually with 50m, 40m, 30m to the center. Among the these net, depth of pursing line was 20∼23m for 50m and 7∼15m for 40m, 30m the depth of net. These results were suitable for interception of fish school in fishing ground, but several problems will be caused by the depth and current of fishing ground.

• Journal of Navigation and Port Research
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• v.47 no.6
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• pp.376-385
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• 2023

Fishing boat capsizing accidents account for more than half of all capsize accidents. These can occur for a variety of reasons, including inexperienced operation, bad weather, and poor maintenance. Due to the size and influence of the industry, technological complexity, and regional diversity, fishing ships are relatively under-researched compared to commercial ships. This study aimed to predict the rolling motion time series of fishing boats using an image-based deep learning model. Image-based deep learning can achieve high performance by learning various patterns in a time series. Three image-based deep learning models were used for this purpose: Xception, ResNet50, and CRNN. Xception and ResNet50 are composed of 177 and 184 layers, respectively, while CRNN is composed of 22 relatively thin layers. The experimental results showed that the Xception deep learning model recorded the lowest Symmetric mean absolute percentage error(sMAPE) of 0.04291 and Root Mean Squared Error(RMSE) of 0.0198. ResNet50 and CRNN recorded an RMSE of 0.0217 and 0.022, respectively. This confirms that the models with relatively deeper layers had higher accuracy.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.2
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• pp.87-100
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• 2007

This study was carried out to offer fundamental data for improving the fishing efficiency of the Danish seine. The net height and the shape in the water was measured to analyze the efficiency of the existing Danish seine. And then, an improved fishing gear was developed based on the results and was tested in the field. Measuring devices were attached on center of a ground rope and a head rope. The net height is the spread distance between the ground rope and the head rope, which was measured on the different ratio of buoyancy. The results are obtained as follows. The net height estimated from the design plan of horizontal hanging ratio 0.40 in the existing Danish seine A and B estimated both 4.94m. The net height of the existing Danish seine A and B was respectively 1.8m and 2.3m, which form 36.4% and 46.2% of the net height estimated from the design plan. Buoyancy was changed as 79.5% and 96.2% relative to the sinking force in the existing Danish seine. The net height of 79.5% was 3.95m which increased to 80% of the estimated net height. The other shows the same result with the first case. It is not necessarily that the high buoyancy/sinking force ratio make the high net height, 80% is adequate as the buoyancy/sinking force ratio. In case of the improved Danish seine, the mean net height was about 5.0m, means 58.3% of estimated net height 8.58m.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.223-231
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• 2001

For the purpose of providing the basic data on the improved fishing gear and the man power saving, which contribute to enhance fishing efficiency of set net in the coast of Jeju Island, this study executed the test of fish tank by reducing these actual nets by 1/30 and using the manufactured model nets, and observed and interpreted the behaviors of entering and escaping of the schools of mackerel Scomber japonicus, horse mackerel Trachurus japonicus and rabbit fish Siganus fuscescens. Thereby the result is as follows ; 1. After the elapsed time of 60 seconds, in case of rectangular set net, the ratio for entering by a school of fish marked 50% with mackerel, 18% with horse mackerel and 28% with rabbit fish, and in case of pound net, the ratio for entering net by a school of fish marked 70% with mackerel, 60% with horse mackerel and 30% with rabbit fish. 2. After the elapsed time of 60 seconds, in case of rectangular set net, the ratio for escaping by a school of fish marked 70% with mackerel, 40% with horse mackerel and 24% with rabbit fish, and in case of pound net, the ratio for escaping from net by a school of fish marked 0% with mackerel, 0% with horse mackerel and 3% with rabbit fish. 3. After the elapsed time of 60 seconds, in case of rectangular set net, the ratio for remaining by a school of fish marked 30% with mackerel, 60% with horse mackerel and 76% with rabbit fish, and in case of pound net, the ratio for remaining by a school of fish marked 100% with mackerel, 100% with horse mackerel and 97% with rabbit fish.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.3
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• pp.724-732
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• 2013

The purpose of this study is to obtain a basic data on layout of the trawlers' bridge equipment. The task activities of bridge workers involved in the navigation and fishing operation were analyzed by link analysis methods. The results are as follows. It was found that the movement pattern and frequency of bridge workers are different accordance with the bridge work (navigation, casting net, towing net and hauling net). The central workstation of movement of the bridge workers was a radar workstation, a steering workstation and a trawl winch workstation in the bridge work. But the radar did not show up as the center of movement during the hauling net. Workstations related deeply to the central workstations of the movement on the bridge were as below. Radar workstation was related to a GPS plotter, a microphone location for external communication with VHF and MF/HF equipment and a steering in the case of the navigation, the steering, the GPS plotter and the net monitor in the case of the fishing operation. Steering workstation was related deeply to the GPS plotter, the radar in the case of the navigation, a speed controller, the GPS plotter, a fish finder, the net monitor and the microphone location in the case of the fishing operation. Trawl winch workstation showed deep relation with the GPS plotter and the speed control during the fishing operation. Through this study, it was found that Workstations related deeply to the central workstation of the movement of the bridge workers in accordance with the bridge work. The results of this study might be utilized as the basic data on the bridge layout to minimize the fatigue degree due to a physical movement of the bridge workers.