The aims of this study are to access the status and problems and draft possible solutions of Korean trawl fishery in New Zealand sea. The main target fish species for Korean trawlers in this sea were barracouta, blue mackerel, hake, hoki, jack mackerel, ling, oreo, orange roughy, southern blue whiting, spiny dogfish, squid and silver warehou. The Korean trawl fishery are suffering from a supply of seaman, continuous increasing coast of the counter partner, repair of vessel and seaman supply. It may be useful for getting over these difficulties to build a new trawler with a automatic operation system.

For providing a basic data concerning with a fishing deck layout design of a trawler the authors conducted the video observations about the working activities of crews on the deck in the different layout of two Korean coastal large stern trawlers (gross tonnage: 139). The winch of the trawler-A was installed on the aft of the fishing deck and the trawler-B, on the forward of the fishing deck. The work and activities of the deck hands on both trawlers were observed using the CCD (charge coupled device) camera installed on each trawler's deck for one month from August 3, 2010. The video data was analyzed by the hierarchical task analysis (HTA) method. In results, numbers of tasks to require deck hands during the hauling net and the casting net were 25 and 28 for the trawler-A and 27 and 48 for the trawler-B, respectively. The working processes were represented a same in both of the trawlers. Location for controlling the deck machineries, the location installed trawl winch, kinds of deck machineries, crew's custom for using deck machineries were the factor affecting to the number of the task. In the case of the improvement suggested in the results is carried out, the reduction percentages of the number of task in the trawler-A and trawler-B were estimated as 24.5% and 51.3%, respectively. Through this study it was found that the quantitative analysis is possible for the work processes, work methods and the work contents in the trawler. Also the suggestion for improving the fishing deck layout design of the trawler was possible by finding out the factors increasing the number of tasks and removing the tasks. We expect that the results of this paper are used as a basic data for designing the layout of deck machineries in the trawler in the future.

To suggest a standard concerning with the arrangement of bridge equipment, the authors conducted the video observations with 3CCD (charge coupled device) cameras installed on the ceil of the bridge for monitoring the working activities of two bridge teams (the skipper/mate1 and the skipper/mate2) in a Korean coastal large trawler(gross tonnage: 139) for five days from July 30th. 2010 and analyzed of the data. Work elements coded by the work activities were input on the sheet of work analysis by the time unit of 1 sec according to the time occurred. A single work element among the work activities for every 5 minutes was denoted as the number of occurrence. The frequency of equipment usage was limited only in the usage of the equipment. In the case of the navigation and the towing net two ranks were integrated and analyzed. On the other hand, in the case of the casting net and the hauling net, two processes were integrated to as one and then analyzed separately as two ranks. As the results, 15 elements of work was carried out between two bridge teams for the observation; lookout, radar, GPS plotter, fish finder, net monitor, fishing deck, RPM indicator, rudder angle indicator, compass card, for maneuver; steering, ship speed control, trawl winch operation and external communications, paper works and others. It was found that the work load of the skipper per 5 minutes accordance with the navigation, the casting net, the towing net and the hauling net are 20.5 times, 11.9 times, 38.0 times and 9.5 times respectively, the mates are 65.2 times, 66.5 times, 85.7 times and 59.1 times respectively. The radar was shown the highest frequency of the equipment usage and the next was the fish finder, the GPS plotter and the external communications in the case of the navigation. In the case of the towing net the frequency of usage was high the ranking as the radar, the net monitor, the fish finder, the GPS plotter, the steering system and the external communications. In the case of the integrated process both of the casting and hauling net the trawl winch was shown the highest frequency to the skipper and the next was the GPS plotter and the radar, and the steering system was shown the highest frequency to the mate and the next was the radar, the ship speed control system, the GPS plotter, the net monitor and the fish finder.

The main purpose of this study is to analyse economic feasibility of low-carbon-oriented trawl gear. The results of benefit/cost analysis showed that use of the low-carbon fishing gear is economically feasible. Considering the fuel saving and relatively low CO2 emission by reducing the resistance of gear, net present value by such gear improvement was estimated about 2,430~2,853 million won with the benefit-cost ratio 1.65~1.84 and the internal rate of return 29.18~30.48 percent. Development of low-carbon trawl gear would render significant contributions to reducing CO2 emission in fishing operations and lead to reduce fishing costs due to fuel savings.

Fuel consumption in fisheries is a primary concern due to environmental effects and costs to fishermen. Much research has been carried out to reduce the fuel consumption related to fishing operations. The fuel consumption of fishing gear during fishing operation is generally related to hydrodynamic resistance on the gear. This research demonstrates a new approach using numerical methods to reduce fuel consumption. The results from the simulation were verified with results that mirrored the model experiments. By designing the fishing gear using drawing software, the whole and partial resistance force on the gear can be calculated as a result of simulations. The simulation results will suggest suitable materials or gear structure for reducing the hydrodynamic forces on the gear while maintaining the performance of the gear. Furthermore, the efficiency of low energy used trawl as economic point of view will be dealt. This research will helpful to reduce the GHG emissions from fishing operations and lead to reduce fishing costs due to fuel savings.

The purpose of this study is to identify the flow resistance of the bottom trawl net. The bottom trawl net being used in the training ship of Chonnam National University was selected as a full-scale net, and model nets such as 1/10, 1/25 and 1/50 of the actual net were made. Total resistance of the net part, the height of the net mouth and the flow resistance of components of the net such as wing, bag and cod-end part was measured, converted into full-scale and compared. Additionally, the model rule of Tauti (1934), which has been most frequently used in fishing net modeling experiments, was applied to interpret flow resistance and scale effect of model experiment was investigated. Presumed that the flow resistance R is R=kSr2 against the flow velocity of each net r, resistance coefficient k was calculated by substituting R, r and S of the net. From the result, it was found that k decreases exponentially when u increases which makes k=cr-m. Whereas m of each net is ranged between 0.13-0.16 and there was not significant difference between nets. c does not show big difference in 1/10 and 1/25 model and the value itself was relatively bigger than in 1/50 model. The height of the net mouth of 1/25 and 1/50 model net h decreases exponentially according as r increases to make h=dr-n. Whereas d and n values were almost same in two nets. Additionally, when resistance of cod-end, wing and bag part in 1/25 and 1/50 model nets, both nets showed big resistance in bag part when flow is 1m/s as more than 60%. Wing and cod-end part showed almost same value or wing part had little bit larger value. On the other hand, when reviewing the reasons why both models showed difference in 1/50 model while c value against the resistance coefficient k did not show big difference in 1/10 and 1/25 model, it is inferred that the difference occurred not from material difference but from the difference in net size according to scale. It was judged that they are the scale effects concomitant to the model experiments.

선미식 트롤선은 선미에서 이루어지는 작업의 특징으로 종종 선미트림이 발생한 상태에서 운항을 한다. 선미트림 상태로 장시간 운항 시에는 선박이 가지고 있던 고유한 선체운동특성이 변화하여 선박의 운항 안정성에 나쁜 영향을 끼칠 수 있다. 이에 본 연구에서는 선미트림 변 화에 따른 선미식 트롤선의 종운동 특성을 선박설계 및 해석프로그램인 Maxsurf를 이용하여 평가 및 해석하였다.

Fishing efficiency of a trawl vessel can be enhanced by increasing the swept area per unit time, which can be attained either by increasing the mouth size of the net, or by increasing the towing speed. To improve fishing and fuel efficiency of trawl vessels targeting fishes of greater mobility, in which the towing speed is more critical in determining fishing efficiency, we conducted a series of model tests to evaluate the performance of the newly-designed nozzle propeller before installing it in a trawl vessel to verify its towing speed and fuel efficiency in the sea. By conducting further model tests in the experimental basin, we redesigned the propeller of stern trawler to improve the resistance and propulsion performance. Through actual fishing operations, we evaluated the improvement in fuel and fishing efficiency by installing the new nozzle propeller. The trawling speed increased by 0.6kts at the same engine power (RPM), while the engine margin increased by more than 20%. The increased towing speed by installing the redesigned propeller is expected to enhance fishing performance through increasing the number of hauling- and casting operations per unit times, while shortening the towing duration. Analysis of the Catch-Per-Unit-Effort (CPUE) data indicated that the mean CPUE of trawl fishery increased from 3.04kg/m in year 2007 to 6.15kg/m in year 2008, confirming enhanced fishing efficiency by adopting the redesigned propeller.

To investigate the catches of jack mackerel fishery, a series of fishing experiments was conducted in the high seas of the southeastern Pacific Ocean (30˚S-38˚S, 82˚W-95˚W) during the period of 9 August to 18 December, 2003 by commercial fishing vessel and research vessel. The number of 205 tows fishing was carried out in the southeastern Pacific Ocean. The total catch was 1,988 ton and CPUE was 2.4 ton/hour. CPUE showed high values in the frontal zone during the survey. Main target species caught from the experimental fishing were the jack mackerel, Trachurus murphyi (98.1%) and chub mackerel, Scomber japonicus (1.9%) as bycatch. Body length of the jack mackerel was different between female and male. The high mean catch per unit effort of jack mackerel was showed when the fishing ground of jack mackerel fishery was over the 110˚W in the southeastern Pacific Ocean. But the fluctuation of the catch per unit effort in the western part of fishing ground was not matched with those year. Reliable physical and oceanographical information will be useful for the efficiency of fishing activity. According to the result of monthly movement of center of fishing ground, the fishing activity of jack mackerel fishery was performed northward in the southeastern Pacific Ocean as time passes.

Fuel consumption in fisheries is a primary concern due to environmental effects and costs to fishermen. Much research has been carried out to reduce the fuel consumption related to fishing operations. The fuel consumption of fishing gear during fishing operation is generally related to hydrodynamic resistance on the gear. This research demonstrates a new approach using numerical methods to reduce fuel consumption. By designing the fishing gear using drawing software, the whole and partial resistance force on the gear can be calculated as a result of simulations. The simulation results will suggest suitable materials or gear structure for reducing the hydrodynamic forces on the gear while maintaining the performance of the gear. This research will helpful to reduce the CO2 emissions from fishing operations and lead to reduce fishing costs due to fuel savings.

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.

To fulfill the design requirement from the Algeria owner, Hull form development of a trawl fishing boat was performed. Model test at CWC in INHA Technical collage was carried out to investigate the resistance characteristics and CFD analysis using FLUENT was performed to examine flow patterns and pressure distribution around hull etc. The designed hull form satisfies speed-power requirement of 10.5 knots at installed power. This paper describes the design feature of trawl fishing boat and evaluates the model test results and CFD results. The design constraints for Algeria trawl fishing boat were explained and the speed of the ship was compared with sea trial results.

To examine species composition, abundance and biomass of demersal organisms in the East Sea, bottom trawl survey was conducted at 7 sea areas from 2005 to 2007. A total of 107 species were collected and were composed of 54 fish species, 16 crustacea, and 37 mollusks in the East Sea from 2005 to 2007. Yearly abundance per area which caught by trawl survey in the East Sea from 2005 to 2007 ranged from a high of 292,234inds./km2 in 2005 to a low of 192,092inds./km2 in 2006. The abundance by sea area showed a peak in 76 sea area, and the lowest in 63 sea area. The abundance per area by season showed a peak in summer, and the lowest in spring. The most dominant species in abundance were Clupea pallasii, Neocrangon communis, Chionoecetes opilio. Yearly biomass per area which caught by trawl survey in the East Sea from 2005 to 2007 ranged from a high of 10,322kg/km2 in 2006 to a low of 7,096kg/km2 in 2005. The most dominant species in biomass were Chionoecetes opilio, Clupea pallasii, Dasycottus setiger. The biomass by sea area also showed a peak in 76 sea area, and the lowest in 93 sea area. The abundance by season also showed a peak in summer, and the lowest in spring. As a result of cluster analysis, demersal organisms community of 76 sea area showed a large difference with other sea area, and that of summer showed a large difference with other season.

Trawlers have to a sufficient towing force due to it's characteristics of the high performance. The newly constructed trawler with the conventional propellers shows the sufficient towing force, so that the propeller and engine are optimized. In the 1970s, many trawlers were imported from overseas by Korean fisheries industries. But the engine output degradation with year by year caused the trawlers to decrease the towing speed of the vessels. On the previous studies, the nozzle propeller had not so good efficiency with increasing of resistance in high-speed cruising operation over 15knots. But the trawling operation is just required the higher thrust and towing force, so that the nozzle propeller is very profitable for the it's effectiveness. A new nozzle propeller was designed for the 4,462G/T trawler, Dong-San, operated by Dongwon Industries Co., Ltd. to improve the towing speed, and the model tests were performed. The model ship and model propeller are preciously manufactured and used model tests in basin. The resistance test and propeller open water test were performed for the cases of the half and full loads. The required engine horse power and RPM were evaluated analytically by the speed-power curve, when the trawler was equipped with the nozzle propeller. The results of tests showed that the towing speed 4.85knots on the design load waterline requires the 200 engine RPM and 2,567ps in the delivered horsepower.

Sea experiment for this study was carried out to develop a Trawl Escapement Net(TEN) using net material to improve the survival rate of undersized fishes that escaped from trawls in the Korean southern sea in May and November, 2005. Three kinds of Trawl Escapement Net(TEN) were examined to increase the escapement rate for fishes escaped from the TEN, and total catches in the codend and cover-net were investigated. The main catch species in the experimental fishing trials using a V shape TEN(A type) in May were Korean pomfret(Pampus echinogaster), slimy(Leiognathus nuchalis), gizzard shad(Konosirus punctatus), white croaker(Pennahia argentata) and smelt(Sillago sihama). In the experimental fishing trials using a V shape TEN with a protector for undersized fishes(B type) and a panel shape TEN with a protector(C type) in November, the main catch species were horse mackerel(Trachurus japonicus), sea pike (Sphyraena japonica), large-head hairtail(Trichiurus lepturus), kammal thryssa(Thryssa kammalensis), white croaker(Pennahia argentata), butterfish(Psenopsis anomala) and red gurnard(Lepidotrigla microptera). Most of large-sized fish species like Korean pomfret and Spanish mackerel could not escape through the TEN in the B type and C type. Catches of horse mackerel were highest in the experimental fishing of November and escapement rates for most fish species including horse mackerel were higher in the C type compared with B type.

Estimation of the gear shape and cross section of sweep at mouth of a bottom trawl net was described and applied to the field experiments obtained with the Scanmar system. The shape of the trawl net from wingend to the beginning of codend was assumed to be part of an elliptic cone of which the cross section was ellipse, and that of the float rope be of form yf=afxbf. In case of a bottom trawl with warp 180m long, the radius of ellipse, the cross section of sweep at mouth, the eccentricity of the ellipse, the inclination angle of float rope and the contribution of the side panel to net height were estimated in accordance with towing speed. The horizontal radius of the upper ellipse increased with increasing towing speed, the eccentricity of it became slightly bigger as increasing the towing speed which meant the shape of it being flat. And the inclination angle of the float rope was about between 7 and 12 degrees in case of the above bottom trawl.

The purpose of this study is to develop the jellyfish separator system(JSS) for reducing fishery damage by the increase of jellyfish in the sea area of Korea in summer. First of all, to find the optimum structure of a JSS, six types of JSS in trawl fishery were designed and manufactured, the underwater shape of JSS and the separating process by JSS were observed in the circulating water channel(CWC). And the field experiments were carried out in July and September 2004 in the southern sea of Korea. For the moving path of the jellyfish model in the CWC, in case that the model was larger than the mesh size of the separator net, it was guided toward the lower part of the separator net by the guiding net and discharged through the outlet. In case that the model was smaller than the mesh size of the separator net, some models which passed through the upper part of the guiding net were smaller than the mesh size of the guiding net and discharged through the outlet and most of the model which passed through the lower part of the guiding net moved to the codend passing through the separator net. According to the field experiment result, the optimum tilt angle of separator net was inferred 20˚ that the discharge rate of jellyfish was higher than the other tilt angle of separator net and the optimum structure of JSS was inferred GS type(consists of guiding net and separator net) that the discharge rate of jellyfish was higher than S type(consists of separator net). It was demamded to carry out more study for the countermeasure to reduce loss of fish.

This paper focuses on the mackerel's visual ability and swimming capability, and aims to describe the behavior in capture and escape process by trawl. The visual sensory systems and reaction behavior based locomotory capability were analyzed and simulated. The ability of fish to see an object depends on the light intensity and the contrast and size of the object. Swimming endurance of the fish is dependent on the swimming speed and the size of the fish. Swimming speeds of the fish are simulated 3 types of the burst speed, the prolonged speed and the sustained speed according to the time they can maintain to swim. The herding and avoiding is typical reaction of the fish to the stimuli of trawl gear in the capture process. These basic behavior patterns of the virtual mackerel to the gear are simulated. This simulation will be helpful to understand the fishing processes and make high selectivity of fishing.

A species composition and population structure of fish, collected 16 times by bottom otter trawl in the coast of Geumo Island, from February 2002 to November 2005, was investigated. The fish species caught by bottom otter trawl from year 2002 to 2005 was entirely 72 species, 41 classes, and 12 orders, and the number of appearance and biomass was 5,999 individuals and 287,902.1g, respectively, being of the Perciformes(31 species and 19 classes; 43.1% in total number of species appeared) as a dominant species. 638 individuals of Leiognathus nuchalis which was 10.6% in total fish were appeared and 465 individuals of Konosirus punctatus(7.8%), 449 individuals of Engraulis japonicus(7.8%). biomass of Sebastes schlegeli was 33,258.7g as a dominant species(11.6% in total fish appeared) and 18,821.1g of Liparis agassizii(6.5%), 16,708.0g of Konosirus punctatus(5.8%). The diversity index of species per months of the collected by a small otter trawl in coastal water of Geumodo from year 2002 to 2005 was 2.860-3.639 and the evenness index was 0.825-0.887 in case of dominance index was 0.224-0.268 against the evenness index. The similarity of community structure per yearly was very high because of the relative difference(0.006), which was the least in 2004 and 2005.

Fishes were caught by a bottom trawl in the Yeo-ja bay of Korea by every three month(March, June, September and December) and seasonal variation of abundance and species composition were studied in 2005. The catches were 1,187kg and were composed of 115 species with 20 hauls by 5 stations. The dominant species caught were Charybdis bimcaulata, Crangon hakodatei, Parapenaeus fissurus, Oratosguilla oratoria, and Thryssa purava. One hundred fifty species were identified as fish(38%), crustacea(20%), mollusca(4%) and others(38%) which including of Asterias amurensis. The amount of species was high in June and September and low in March and December. The diversity index(H') was about 1.2－2.5 and station similarity of fishes caught among the community was 0.009－0.230.