This study aims to investigate effects of the length of the buoy and sand bag line on the loss of webfoot octopus pot. A numerical modeling and simulation was carried out to analyze the process that the pot gear affected by wave using the mass spring model. Through the simulation, tensions of sand bag line under various condition were investigated by length of buoy and sand bag line. The drag force and coefficient k of an artificial shell used in the webfoot octopus pot was obtained from an experiment in a circular water channel, and the coefficient k was applied to the simulation. To verify the accuracy of the simulation model, a simple test was conducted into measuring a rope tension of a hanging shell under flow. Then, the test result was compared with the simulation. The lengths of the buoy line in the simulation were 1.12, 1.41, 1.80, 2.23, 2.69, and 3.17 times of water depth. The lengths of sand bag line were 10, 20, 30, and 40 meters, and conditions of water depth were 8, 15, 22 meters. 4 meter height and 8 second period of wave were applied to all simulations. As a results, the tension of the sand bag line was decreased as the buoy and sand bag line were increased. The minimum tension of the sand bag line was appeared in conditions that the length of the buoy line is twice of water depth and the sand bag line length is over 40 meters (except in case of depth 8 meters.).

This study aims to reduce the force exerted to the buoy of the gillnet by wave and current. Five buoy models were selected for experiments and their rope tensions under wave and current action were compared. Five models were EL (ellipsoid), EL-H (ellipsoid-hole), SL (streamlined body), SP (sphere) and CL (cylinder, traditional type). In the first experiment, the Five models were tested without any attachment. In the second experiment, a flagpole was attached to each model. As a result, in the condition without flagpole, the tensions of four models with the exception of the CL were about a half of that of the CL. In the condition with flagpole, the tension of all models was twice larger than that without flagpole. Thus, a new model was suggested to improve the problem, which has a combined body that of a flagpole and a buoy Three new models of CL-L (long and thin cylinder), LF (leaf shape) and LF-F (leaf shape with fin) were designed. Also a cylinder type (CLD) with a flagpole as a control was included in the experiment. As a result, the LF-F had the smallest tension and a half tension of the CLD. Therefore, it is supposed that the flagpole and buoy combined model could reduce the tension on buoy rope and contribute to improve the gillnet loss problem.

This study investigates the development of an automatic lightening buoy that can indicate an aquaculture cage at night or in rough weather. The energy for the light is generated by the linear motion of a magnet along with a coil inside the buoy as the waves cause the buoy to oscillate up and down. The principle of the magnet motion is different between the magnet and body of the buoy because the movement of the latter is dependent on the surface wave, while the former is affected by the damper. To obtain a quantitative performance of the buoy, the voltage as well as up and down motion produced by several waves were measured in the wave tank. A shorter wave period, i.e., faster motion, of the magnet produced a brighter light. It is expected that this study can aid in deciding the optimum design of a buoy capable of producing a bright light at any aquaculture site affected by sea or fresh water waves.

The Fishing gear loss has been repeated every year in the West Sea; however, there has been no solution. So fisher men have undergone economic loss every year. Thus it is required to reduce the loss of fishing gear. In this study to find out the reason that the fishing gear is lost in the Sea, 10 years data of wave and current for 6 locations in the West Sea were investigated and a numerical modelling were conducted into the behaviour of a gillnet in wave and current. The fishing gear was modelled with the mass spring model. As a result, it came out into the open that the location where fishing gear loss occurred most frequently was Choongnam province. The height of the maximum significant wave in this province was 6.7 m and the period of that was 4.4 second. The maximum current speed was 0.7 m/s. As a result of simulation with these data, it was revealed that the buoy is one of the reasons to decrease the holding power of the gillnet. For example, the tension of anchor rope was decreased to 50% while the drag coefficient or volume of buoy was decreased to 25%. So it is predicted that an improvement of the buoy contributes to the reduction of the gillnet loss.

The coastal stow net (stow net hereafter) in Korea is one of the major fishing methods for yellow croaker (Larimichthys polyactis), ribbon fish (Trichiurus lepturus), and anchovy (Engraulis japonicus). In terms of energy efficiency, the stow net fishery is more competitive than towing fishing gears such as trawl gears. The fishing vessels in stow net fishery have consumed less fossil fuel and also have had less carbon dioxide emission into the atmosphere. however, the stow net fishery is necessary to be regulated due to its increased output of the fleet. Therefore, it is required for fisheries authorities to manage the fishing capacity or fishing power for the assurance of fishery’s sustainability. For fisheries management authorities, it is necessary to quantify data related to fishing capacity and fishing power to deploy fishery policy in a sustainable way. In terms of data for decision-making, Data envelopment analysis (DEA) method was conducted to estimate fishing capacity. Fishing power index (FPI) was also applied to calculate relative fishing power to approach the problem in a quantitative way.

In this study, we confirmed that the pesticides flow out into streams during rainfall by the way of helicopter spraying. The maximum concentration was 23 pg·mL-1 and the distribution of concentrations showed similar to the normal distribution. The runoff characteristics of insecticides using helicopter spraying was affected by the elapsed time of the start from spraying until rainy days and rainfall intensity. The pesticide concentrations of sample ranged from 0.65 to 3.04 pg·mL-1. Fish kill did not occurred in the stream and the lake cause of the pesticides runoff. Aquatic animals, such as Orthrias toni, Rhinogobius brunneus, tadpole etc. were still alive in the stream. It indicates that this class of pesticide does not cause toxic to fish by runoff event. However, the honey bee kill event was reported in the spray region during the helicopter spraying period. The further study such as ecotoxicity test is needed to reveal the pesticides effect reach to the ecosystem.

Starfish, a species of Echinoderm, is widely known as a predator on benthic invertebrate. A series of fishing experiments was carried out in the western coastal waters of Korea from September, 2011 to November, 2012, using the drum–shaped pots of different mesh sizes (17.1, 24.8, 35.3, 39.8, and 48.3 ㎜) to describe the composition of the catch species and the mesh selectivity of the pot for starfish. Some species including fish, crab, and starfish were caught in the experimental pots. The SELECT (Share Each Length’s Catch Total) method was applied to describe the selectivity of the pot for starfish Asterina pectinifera. The master selection curve was estimated to be s(R) = exp(10.358R–4.086) / [1+exp(10.358R–4.086)], where R is the ratio of arm length to mesh size. The relative arm length of 50% retention was 0.395, and the selection range was 0.212. The results should be helpful to understand the relationship between the catch size of starfish and the mesh size of pot.

A series of field tests to estimate the size selectivity of monofilament and multifilament gill net for marbled sole, Pleuronectes yokohamae, were carried out 12 times with five different mesh sizes (86.6, 101.0, 121.2, 137.7 and 151.5mm) in the western sea of Korea from 2007 to 2009. The master selection curve was estimated by the extended Kitahara’s method. The total number of catch species was 23 and that of catch was 1,688 in the field tests. Marbled sole of total catch was 1,150 with 68.1 percent. In the monofilament trammel net, the optimum value of total length (TL) per mesh size (m) for 1.0 of retention probability was estimated 0.280 and the values of TL/m were estimated to be 0.187, 0.201, 0.210, 0.218 and 0.226 when the retention probability were 0.1, 0.2, 0.3, 0.4 and 0.5, respectively. In the multifilament trammel net, the optimum value of TL/m for 1.0 of retention probability was estimated 0.307 and the values of TL/m were estimated to be 0.195, 0.211, 0.222, 0.232 and 0.241 when the retention probability were 0.1, 0.2, 0.3, 0.4 and 0.5, respectively.

To investigate the catching efficiency of a biodegradable round trap for a swimming crab (Portunus trituberculatus), four types of material (two types of biodegradable net, one type of biodegradable plus polyethylene net and one type of polyethylene net) for traps were used in the field test, and the field tests were carried out 11 times in the Boryeong fishing ground of Korea, 2012∼2013. The catching efficiency of four type traps was analyzed by catch per trap, weight per trap and mean weight per individual of small and large size swimming crab. Statistical Kruskal-Wallis test was carried out to verify the significant difference for the efficiency between types of material. The catch in number of swimming crab was 9,015 and formed about 94.3% of total catch. In the results of catching efficiency of traps, there was a little difference in catch per trap, weight per trap and mean weight per individual of swimming crab in-situ data. But there was no significant difference in catching efficiency between the biodegradable traps and the PE trap (P>0.05), so it’s needed to use widely a biodegradable trap for the conservation and sustainable management of swimming crab resources.

The difference of mooring tension by type of buoy was investigated in the circulating water channel and the wave tank for deducting the most stable buoy from the current and the wave condition. 5 types of buoy made up of short cylinder laid vertically (CL-V), short cylinder laid horizontally (CL-H), capsule (CS), sphere (SP) and long cylinder (CL-L) were used for experiments. A mooring line and a weight were connected with each buoy. A tensile gauge was installed between a mooring line and a weight. All buoy’s mooring tension was measured at the same time for the wave test with periods of 1.5~3.0 sec and wave heights of 0.1~0.3 m, and the current test with flow speeds of 0.2~1.0 m/sec. As a result, the order of tension value in the wave test was CL-H > CL-V > SP > CS > CL-L. In the current test CL-V and CL-H were recorded in the largest tension value, whereas SP has the smallest tension value. So it seems that SP buoy is the most effective in the location affected by fast current. CS is predicted to be suitable for a location that influence of wave is important more than that of current if practical use in the field is considered. And it was found that the difference of mooring tension among buoys in wave is related to the product of the cross sectional area and the drag coefficient for the buoy’s bottom side in high wave height. The factor for the current condition was not found. But it was supposed to be related to complex factors like a dimension and a shape by buoy’s posture to flow.

To estimate the mesh selectivity of gillnet for ocellate spot skate (Okamejei kenojei), the field tests were carried out 12 times with six different mesh sizes (121.2mm, 137.7mm, 151.5mm, 168.3mm, 178.2mm, 189.4mm) in the coastal waters of Taean, Chungcheongnamdo of Korea, 2010~2011. In the field tests, the total number of species was 31, and that of catch was 1,410 and the total weight was 618,006g. The number and weight of ocellate spot skate which is main target in this study were 1,004 and 434,592g, respectively. The catch in number of ocellate spot skate occupied about 71.2% in total catch. The others of catch species were marbled sole (8.4%), sea raven (4.4%), japanese swimming crab (4.2%) and flatfish (4.1%) and so on. The range of body disk width (DW) of ocellate spot skates which were caught in this study was 15.2~35cm and the mode was 27~29cm. The estimation equation of mesh selectivity using the extended Kitahara's method was expressed as s (R)=s(DW/m)=exp{(-0.56R3-1.80R2+12.96R-9.99)-4.26}. The optimum value of DW/m for 1.0 of retention probability in this estimation equation was estimated 1.899 and DW/m was estimated to be 1.194, 1.314, 1.395, 1.461 and 1.520 when the retention probability were 0.1, 0.2, 0.3, 0.4 and 0.5, respectively. When applied to the retention probability of 0.5, the optimum mesh size was estimated to be 177.0mm on first maturity disk width 26.9cm of ocellate spot skate.

To study the catching efficiency of biodegradable trammel net for swimming crab (Portunus trituberculatus), three types (biodegradable, monofilament and multifilament) of trammel nets were used in the field test, and the tests were carried out 16 times with two different mesh sizes (105mm and 160mm) in the Yeonpyeong fishing ground of Korea, 2009~2011. The catching efficiency of three type nets was analyzed by catch in number, catch in weight and average weight per individual of small and large size swimming crab by net types and mesh sizes. Statistical T-test was also carried out to verify the efficiency between the three types of nets. The results are as follows. The catch in number of swimming crab was 24,667 and formed about 81.0% of total catch. Of all swimming crab catch, small swimming crabs with less than 64mm in carapace length which is a prohibited landing size by law formed 48.1%, larger swimming crabs with more than 64mm in carapace length which is a landing size formed 51.9%. In 105mm mesh size trammel net test, the catch share in number of small size swimming crab by biodegradable trammel net was 47.5% in comparison with multifilament trammel net and 74.2% in comparison with monofilament trammel net, so biodegradable trammel net has more protective effects on small size swimming crab than other types of trammel nets. The protective effects for small size swimming crab by biodegradable trammel net was 25.8~52.5% in comparison with other types of trammel nets. The catch share in weight of large size swimming crab by biodegradable trammel net was 98.3% in comparison with multifilament trammel net and 92.3% in comparison with monofilament trammel net, so biodegradable trammel net has a similar catch efficiency to multifilament trammel net. The results of 160mm mesh size trammel net test have shown similar results of 105mm mesh size trammel net test. This study shows that biodegradable trammel net is a more useful fishing gear than multifilament and monofilament trammel net because biodegradable trammel net has lower catch rate than other types of nets in small size swimming crab and similar catch rate than multifilament trammel net which is a well used net by fishermen.

고분자는 우수한 투과선택도 및 가공성으로 인하여 여러 기체 혼합물의 분리를 위한 막의 소재로 널리 이용되고 있다. 본 연구에서는 polyamide 복합막을 이용하여 CH4 및 CO2 혼합기체의 분리특성에 관한 연구를 수행하였다. 본 연구를 위한 모사 기체로는 순수 메탄과 이산화탄소를 혼합하여 사용하였으며, 서로 다른 운전조건에서의 투과실험을 수행하였다. 주입 기체의 유량은 800~1000 cm3/min으로 변화시켰으며, stage cuts의 변화는 50~60 %로 하였다. 또한 분리막의 운전 온도는 30~70℃에서 변화시켰으며 기체의 초기 주입압력은 6 bar로 설정하였다. 각 실험조건에서 메탄과 이산화탄소의 투과도를 평가하였고 이때 permeate에서의 이산화탄소에 대한 선택도를 함께 평가하였다. 또한 본 연구에서는 Arrhenius plots를 이용하여 메탄과 이산화탄소의 분리막에 대한 투과 활성화 에너지를 얻었다.

This study aims to analyze the performance of a submersible fish cage which was designed for developing an economical cage system can be applied in korean aquaculture environment easily. To analyze the performance of the designed cage a model test was carried out. In the test, inclination changes of the upper frame and mooring tensions of model cage were measured during the submerging and surfacing motion in still water and wave condition (period: 2s, wave height: 0.1, 0.2, 0.3m). As a result, in the still water condition the model cage kept horizontal balance and inclination degree of the upper frame was about 1˚. In the wave condition, the model cage showed bilateral symmetric up-and-down motion but the average inclination degree of the upper frame was about 0˚. When the model cage reached at a depth of 1m, the up-and-down motion of the cage was decreased by 12% compared with that of at the surface (period 2s, height 0.3m). In the same wave condition, the maximum and average line tension under the bottom position were about 8% and 11% respectively compared with that of at surface.

Biodegradable octopus pot was developed to reduce plastic pollution problem in the sea and fishing trouble between fishermen. It can be expect to recycle other wasted biodegrade fishing gear. Experimental fishing was carried out to understand the difference in fishing efficiency between Polyethylene (PE) octopus pots and biodegradable (Polybutylene Succinate and Polybutylene adipate-co-terephthalate) octopus pots which was tried to make in this study in the sea. There were caught by 237 numbers of fishing during the experimental period. Among the 237 numbers of fishing, 160 or 67.5% were PE pots which were more than the biodegradable pots. A comparison of the monthly catches between the PE pots and biodegradable pots shows that the catches were overall higher in the PE pots than in the other pots. The result is very similar with the comparison of total catches by each type of the pots. In terms of bycatch, the number of species, amount of catches and the number of fishing with bycatch were more significant in the biodegradable pots than in the PE pots.

In order to describe the performance of a wedge type jellyfish excluder device, a series of fishing experiments was carried out in the coastal areas of Yokji Island, southern Korea in 2009, using a trawl net with a cover net. The body size and weight of each individual (fish or jellyfish) caught in the experimental fishing were measured. In the case of giant jellyfish the bell diameter and weight were measured. The catch species was composed of giant jellyfish (Nemopilema nomurai), silver croaker (Pennahia argentata), yellow croaker (Larimichthys polyactics), finespotted flounder (Pleuronichthys cornutus), largehead hairtail (Trichiuruslepturus), melon seed (Psenopsisanomala) and so on. The weight ratio and individual ratio of total fish escaped through the outlet of the excluder device were 0.322 and 0.320, respectively. The weight ratios of giant jellyfish excluded from the trawl net ranged from 0.740 to 0.921 (average 0.852/haul). It means that the wedge type jellyfish excluder device performed well and allowed the most of the giant jellyfish to exclude through the trawl net. The approximately 70% of fish entered in trawl net was caught. The wedge type excluder device needs some improvements to minimize the fish escape from the trawl nets in the future.

Test fishing was carried out using six kinds of different mesh sizes (20, 22, 24, 28, 35, 40mm) for springnet-pot to study bycatches according to the mesh size and catches survey was done for another one (mesh size : 22mm, entrance round : 350mm) in Geo-je & Tong-young waters of Korea. On the first sea experiment, it was thought that suitable mesh size of spring-net-pot catching conger-eel over 35cm with decreasing the catches of conger-eel (Conger myriaster) below 35cm was 24mm. On the second sea experiment, commercial catches were crabs (Charybdis bimaculata), octopus minor (Octopus variabilis) and others including conger-eel, and catches proportion was 60% of total catches weights. There was no big difference for the monthly catches. Self-consumption catches were 9 species including conger-eel below 35cm holding 50% of catches in the side of weights. There were 40% of bycatches for the catches weights and 63% for catches numbers in the 22mm mesh size of spring-net-pot having entrance round over 140mm. It showed that 50% of catches weights were discarded.

In this research, the submersible fish cage was designed to avoid structural and biological damage during harsh sea conditions. The submersible cage system consists of netting, mooring ropes, a floating collar, floats, sinkers and anchors. Whole elements of the cage were modeled on the mass-spring model. The computer simulations were carried out to investigate the dynamic behavior of the cage and to calculate mooring line tension subjected to tidal currents and waves. As expected, the tension values in the mooring line of the submerged position are 36% less compared to that of the surface cage under the same loading conditions. As the wave was used in combination with the current velocity of 1m/s, the average tensile load for the submerged cage showed 85% of the value for the floating cage. The simulation results provide an improved understanding of the behaviors of the structure and valuable information on the optimized design of the cage system exposed to open ocean environmental factors.