• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.2
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• pp.90-96
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• 1997

Until now the research was usually related in the fishing basket for crab charybdis japonica, concentrated one's effort to modification on the construction, shape, number of entrance of fishing basket etc.. But there's not make good used to the basically habit, shelter behavior of crab. etc., and was not fundamentally modified to the ability attracting the crab on net fishing basket. In this paper, first of all investigated to the behavior of crab in water tank and then two types modification fishing baskets could the increasing to ability attracting of crab on fishing basket were designed from the result obtained in this experiment and compared with modificated net fishing basket by Kim.Go(1987.1990) at a field and tank experiment. The results obtained are summarized as follows : 1. Being the fishing baskets had dropped in the tank bottom, the touched rate and reacted rate of crab according the elapsed time agree with to experiment of Kim.Go(1987.1990)in the mainly. however, in case of plate type tangle net, the touched rate of crab increased for a short time and then decreased and the reacted rate increased in a hurry to show a maximum and then was established. 2. The beginning catch time of crab was shortest in the plate type tangle net than the any fishing baskets because it's immediately entangled if the crab was touched only a part of body on net and latest in the net fishing basket. 3. A distance of between the touched rate and the reacted rate curve were the most short, wide in the plate type tangle net. therefore, the ability attracting of crab was excellent than the any fishing baskets and in case of pipe type fishing baskets, between the 150mm and 250mm seemed not difference and showed a tendency to increasing against the net fishing baskets. 4. Pipe type fishing baskets seemed to become a good shelting place for the crab because it showed a tendency to stagnate at the inside in that. 5. The mean catch per pot of crab among the net fishing basket, pipe type fishing baskets, plate type tangle net were highest in the pipe type fishing baskets than the net fishing basket and lowest plate type tangle net. Therefore it showed to difference against the tank experiment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.4
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• pp.348-354
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• 1987

The behavior of crab, Charybdis japonica h. Milne EDWARDS, to the net pots with baits was investigated alternately in the experimental tanks. One of the pots being dropped on the tank bottom, the crabs touched it to obtain the bait probably reacted by their senses of smell and sight, and increased gradually in the number of touch to show a maximum within 30 min. The crabs, if touched circular pots, were guided more easily to the pot entrances than the case of touching square ones, but the guidance from the vicinity of the entrances into the pots was easier in the square. When the crabs entered the pots, they always showed a sharp precaution. However, most of enterings were made mainly within 30 minutes and easier in pots with lower entrances. If 30 min. elapsed, the entering was little made by the decrease in the number of touch and the getting-out was remarkable, especially in pots with low entrances. But, in all the pots the getting-out was hampered by the drawing of the entrance tips into the pots. In case in which flappers were attached to the entrance tips, the entering was very hampered, hut the getting-out was not shown.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.1
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• pp.45-50
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• 1990

The basic investigation of the sea eel pots fisheries by questionnarie observation and dimension of the pots by fishing operation were carried out in order to develop for mechanical hauling system with 20~50 gross tonnage fishing boats from June to December, 1988. Number and weight of fish per pot between smaller diameter 11cm and larger 13cm of the pot have no significance so that the drag of the smaller pots can be decreased about 20% than the larger pots. The operating time by two men from opening to closing with screwing lock entrance was slightly faster than that by three men with knotting entrance even though the losses with two kinds of entrances while fishing operation were about the same. It was very reasonable that stone and lead sinker on the main line were substitute for two or three lead core P.P rope to make it smooth surface of the main line for mechanization of the continuous fishing operation.

• Korean Journal of Ecology and Environment
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• v.49 no.2
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• pp.110-123
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• 2016

In order to obtain scientific information for the conservation of Utricularia japonica Makino, rare plant species, we investigated life history, phenology, growth and distribution in the east coastal region of Korea. Seven habitats of U. japonica were confirmed in this study. Turion of U. japonica rests overwinter at the bottom and ripens at the water surface and then usually germinate and sprout when the water warms in spring. A single shoot grown from turion divided into several shoots. Shoot decomposition started in October and formed a new turion at the end of the decomposed shoot. Flowering period was from early July to late October. Percentage of flowering ramets was significantly low as 6.3%. U. japonica showed the fastest growth rate from April to July, the maximum growth in August and the highest biomass in October. U. japonica tended to be concentrated in larger ramets in the water depth of 50 cm~150 cm in Cheonjin lake. The main factors affecting the growth of U. japonica were water temperature and turbidity. The establishment and growth of U. japonica in Cheonjin lake were determined by responses to water temperature with seasonal change and to light conditions caused by the different plants. These conditions affect the temporal and spatial distribution of U. japonica and population change. The findings of this study would be helpful to provide the basic information needed for the conservation and restoration of U. japonica.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.149-155
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• 2002

Sea-eels caught by fishing boat and trawl were analyzed to investigate feeding status and individual growth of sea-eels caught from the lost plastic sea-eel Pot which is estimated at the ghost fishing Average length of sea-eel caught from fishing boat and test fishing was 33.6cm, 48.9cm for trawl and 45.6cm for the lost plastic sea-eel pot, respectively. The length frequency distribution is the same as the fact that sea-eel goes to the offshore from the coastal waters according to the getting growth. Sea-eel rate having empty stomach were 5.0% for fishing boat, 4.2% for trawl and the empty stomach rate of sea-eel was the highest as 87.6% in the lost pot. Sea-eel rate feeding fish as prey were 98.7% for fishing boat, 78.8% for trawl and 63.3% for the lost pot, respectively and other preys were crustacean and cephalopod. Fatness index calculated using weight and length were 1.514 for trawl catches and 1.292 for the lost pot and the difference was 15% between trawl catches and the lost pot. There also was difference at the 5% significance level in the result of t-test of Covariance Analysis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.4
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• pp.157-162
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• 1987

The basic experiments on the plastic sea eel pots used in fishing were carried out in order to investigate the elasticity of the funnel ribs, hydrodynamic resistance, sinking time and diffusion of the bait from June to October, 1987. The elasticity of the bamboo funnel ribs was higher than that of the polypropylene ribs up to the load 150g. The hydrodynamic resistance R (kg) of the pots towing to the head direction horizontally in relation to towing velocity V (m/sec) was expressed as following formula; R=0.36V super(2.01) and coefficient of drag C sub(D) was 0.52. The sinking times of the covered pots by tape fully or partially were late 1-2 second than the typical pots within the water depth 7.5m. The diffusion tendency through the covered pots using dye and sardine extracts solution was concentrated to the entrance more than the typical pots. However, fishing efficiency as number and weight of fish per pots for nine times fishing operation was revealed no difference between the covered pots and the typical pots.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.10a
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• pp.19-22
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• 2003

통발어업은 어구 조작을 위한 선박 의존도가 적고, 어구를 예인하지 않아 배의 속력이나 기관 마력을 그다지 크게 할 필요성이 없으므로 유류 사용량이 적으며, 저인망이나 연승 등으로 조업이 곤란한 기복이 심한 해저나 심해에서도 조업이 가능하다는 장점이 있다. 본 연구실에서는 통발 어구에 대해 미성어를 탈출하게 하여 보호하고, 성숙한 개체만을 선택적으로 어획할 수 있는 자원관리형 통발 어구어법 개발에 관한 연구가 수행 중에 있으며, 현장실험을 통해 어구에 대한 어획선택성, 자원상태와 어획강도 등에 관한 연구를 수행하고 있다. (중략)

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.19-29
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• 2022

The result of a questionnaire survey conducted on fishermen using coastal fish traps shows that fall accidents during trap dropping and pulling constitute the highest proportion of accidents at 42.1 %, whereas slipping accidents on the deck or stricture accidents to the body due to the trap winding device constitute 21.1 % each. In addition, 53.2 % of all surveyed subjects responded that trap pulling is the most dangerous task, followed by fish sorting 33.8 %, and trap dropping 9.1 %. As for the main items requested by fishermen for improving the trap winding device, 36.8 % indicated a method to easily lift the trap from the water to the work deck, and 31.6 % indicated a method to overcome the rope tension and prevent slip when pulling the trap to reduce the accidents. The small trap fishing vessel winding device proposed herein can increase the winding force by strengthening the rope contact area and friction coefficient via an appropriate contact angle between the driving roller of the winding device and the rope. When the contact angles between the driving roller and the rope are 1°, 5°, 9°, 14° and 19°, the rope tension showed a difference according to each contact angle. When the contact angle is 9°, the rope tension is the highest at 392.62 kgf. Based on these experimental results, a prototype winding device is manufactured, and 25 traps are installed on a rope with a total length of 100 m at 4 m intervals in the sea, and then the rope tension is measured during trap pulling. As a result, the rope tension increases rapidly at the initial stage of trap pulling and shows the highest value of 31.89 kgf, which subsequently decreases significantly. Therefore, it is appropriate to design the winding force of a small trap fishing vessel winding device based on the maximum tension value of the rope specified at the beginning of the trap pulling operation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.247-254
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• 2004

The mesh selectivity of the drum net fish trap for elkhorn sculpin(Alcichthys alcicornis) in the estern sea of Korea was described. The selection curve for the elkhorn sculpin caught from the experiments between June 2003 and December 2003 was by SELECT(Share Each Length Class's Catch Total)model and by Kitahaa's method to a polynomial equation and two parameter logistic selection curve. The selection curve by SELECT model showed to be equal probability of entrance of the elkhorn sculpin in the large(55mm) and small(20mm) mesh traps by minimum AIC (Akaike Information Criteria). The equation of selectivity curve obtained by Kitahara's method using a logistic function with least square method was $s(R)\;=\;\frac{1}{1+exp(-0.3545R+2.141)$, where R=1/m, and/and m are total length and mesh size, respectively. The mesh selectivity curve showed that the current regulated mesh size(35mm) for the trap was corresponded to 21.4cm in the $L_{50}$of the selection curve for the elkhorn sculpin.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2005.05a
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• pp.130-131
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• 2005