• 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.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.79-80
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• 2001

저층트롤 어업은 주로 고가의 저서성 어족을 대상으로 조업이 이루어지고, 어구의 구조나 규모가 다양하며 발줄은 어구의 접지성을 유지하는 기능과 함께 어군을 망구에 구집 하는 역활을 한다. 저층 예망어구는 해저를 소해 하면서 예방하기 때문에 해저와의 마찰 저항이 많을 뿐만 아니라 뻘을 뜨거나 장애물에 걸리는 사고가 발생하기도 하여, 어획성능에도 많은 영향을 받는다. 이에 대한 연구로써, 독일에서는 빔 트롤의 체인의 형태에 따른 모형 트롤어구의 역학적 특성을 실험(1997, Uwe Richter)한 바가 있고, 일본에서도 발줄의 형상에 관한 연구(1992,Fuwa)가 있다. (중략)

• Journal of Fisheries and Marine Sciences Education
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• v.15 no.1
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• pp.47-56
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• 2003

Recently with the conclusion of fisheries agreements between Korea and Japan, and between Korea and China, trawlers in korea must operate in smaller fishing ground than before. As a result of this, the possibilities of collisionin increases gradually between trawlers under operation in this area. Authors performed a series of experiments on board to give the information of collision avoiding action to navigators of trawlers. The obtained results are summerized as follows : 1. The greater the rudder angle, the smaller the value of T, but there is no big diffierence in K due to rudder angle. 2. The greatest distance is to be kept by the give way vessel to avoid collision when the crossing course angle is $70^{\circ}{\sim}90^{\circ}$. In this case the safety minimum approaching distance must be more than 5 times of her own length. 3. Risk of collision in crossing is more greater in obtuse situation than in acute one. 4. The navigator of the give way vessel must take an action to avoid collisions outside of the minimum safety approaching distance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.3
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• pp.241-258
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• 1998

The experimental demersal trawl surveys to provide the essential information for the assessment, management and utilization of commercially important fish stocks in the southern waters of Korea were carried out during five research cruises between October 1996 and October 1997 by the training ship “KAYA” of Pukyong National University. The biological sampling was conducted by using the trawl net with a cover net of 36 mm in mesh size at 64 planned trawl stations during daylight to identify the biological characteristics of fish. Each catch was standardized into catch per unit of time and the catches at each trawl station were sorted, weighed and counted by species. The changes in catches of each fish species and the shifts in dominant species by seasions and sampling regions in the research area were analyzed, and the abundance of fish was estimated from the relationship between the trawl catches and the volume of the water column sampled by demersal trawls. The results obtained can be summarized as follows : 1. During the 64 demersal trawls conducted in the southern waters of Korea, 129 species including 112 species of fishes, 8 species of Cephalopoda and 7 species of Crustacea, were identified Also, during the 1996 and 1997 trawl surveys in the reseach area, a large number of commercially important species with small differences in proportion was found. me proportion of Japanese horse mackerel which comprised 19.8% of the total catch by weight was highest, followed by chub mackerel(15.0%), swordtip squid(9.0%), redwing searobin(6.2%), konoshiro gizzard shad(6.1%), Japanese flying squid(5.8%), silver pomfet(5.1%), blackmouth goosefish(5.1%), etc. Swordtip squid, Japanese flying squid, blackmouth goosefish and blackthroat seaperch were among the dominant species in all seasons with a relatively high and stab1e proportion(3.6~9.0%), and were widely distributed in the entire southern water of Korea. 2. The catch rates by cover net varied at 0.7~91.9% by weight of the total trawl catch by codend and cover net at 64 planned trawl stations and the mean catch rate was 44.4%. Species comprising a major portion of the catches by cover net mainly were swordtip squid, konoshiro gizzard shad, the juveniles of Japanese horse mackerel, blackthroat seaperch and chub mackerel, etc. 3. The distribution density of fish in terms of biomass per unit volume which derived from the catch data by 63 bottom trawl hauls in the southern waters of Korea ranged from 17.9 $\times$ 10-6 to 1,440.9 $\times$ 10-6kg/m3 with the mean value of 153.8 $\times$ 10-6 kg/m3. These fish densities varied between seasons, location of sampling stations and sea conditions. From these results, it is worth noting that the catch composition of multispecies and the increased occurrence of small fish in the southern waters of Korea may also result in new problems in determining the total allowable catch(TAC) levels for economically important species.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.71-72
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• 2001

접근하는 어군을 기다려서 어획하는 연안의 정치망과 같은 고정식 어구는 지리적인 여건과 지형적인 특성이 해황의 변동과 더불어 어획량에 직접적인 영향을 미치게 된다. 그러나 어군을 쫓아서 조업하는 어구의 경우는 어구ㆍ어법의 개량 등을 통하여 극복할 수 있고, 해황의 변동으로 인한 어획량의 감소가 있을 경우에도 어군을 찾아서 어장을 이동할 수 있는 등의 장점이 있다. (중략)

• Proceedings of the Korean Aquaculture Society Conference
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• 2006.05a
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• pp.31-32
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• 2006

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.327-330
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• 2010

어선의 해양사고 중 가장 많이 발생하는 충돌사고의 경우 선박 운항자의 졸음 등의 이유로 경계를 소홀이 하여 발생하는 경우와 어로 작업 중 접근하고 있는 상대선을 발견하고도 어로 작업 특성상 조종성능이 극도로 제한되어 적절한 피항 동작을 하지 못하여 발생한 경우가 대부분이며 이는 성어기의 어선 조업 특성상 선박의 조종업무를 수행할 수 있는 선장의 업무과중에 의한 피로누적과 어로 작업 특성상의 조종성능제한에 의해 기인한 것으로 판단되어 동해지방해양안전심판원 관할구역 내에서 주로 행해지는 자망, 채낚기, 기선저인망, 동해구 트롤어업의 조업 형태에 따른 어선 선원의 작업 여건과 각 어업별 어로 작업 중인 선박의 운항 성능에 대해 알아보고 충돌사고 방지를 위한 대책을 제안하고자 한다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.106-116
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• 2001

A serious of studies on the fishing gear and system of the East Sea trawl fishery was carried out to improve the fishing efficiency and the working conditions. As the first step of these studies, the fishing gear and system of the traditional East Sea trawl were checked in order to solve the some problems, such as the poor sheering efficiency of net mouth, the inconvenient fishing system of the side trawl and etc. And then the fishing system was reorganized from the side trawl into the stern trawl by setting up the net drum system on the stern deck, and introduction of two types of new designed nets, one for mainly the midwater trawl and the other for the bottom trawl. The results of the field experiment on the modified system and nets can be summarized as follows : 1. the modified system was well worked and could save the man-labour by about 80%. 2. The sheering efficiency of the improved net, A type was improved to 20 m height and 30 m width in the net mouth, and that of B type net, to 10 m height and 33 m width, compared with 1.5 m height and 15 m width in the traditional net. 3. Catch efficiency of pink shrimp in A or B type net was better about 3 or 5 times than that of traditional net, and in B net, for herring and other bottom fishes is better about 2 times than that of the traditional net.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.54-59
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• 2000

This paper presents a control system that uses a fuzzy algorithm in controlling the depth of a model midwater trawl net, and experimental results carried out in the circulating water channel by using a model trawl winch system.The fuzzy controller calculates the length of the warp to be changed, based on the depth error between the desired depth and actual depth of the model trawl net and the ratio of change in the depth error. The error and the error change are calculated every sampling time. Then the control input, i.e. desirable length of the warp, is determined by inference from the linguistic control rules which an experienced captain or navigator uses in controlling the depth of the trawl winch controller and the length of the warp is changed. Two kinds of fuzzy control rules were tested, one was obtained from the actual operations used by a skilled skipper or navigator, and the other was a modified from the former by considering the hydrodynamic characteristics of the model trawl system.Two kinds of fuzzy control were tested, one was obtained fro the actual operations used by a skilled skipper or navigator, and the other was a modified from the former by considering the hydrodynamic characteristics of the model trawl system.The results of these model experiments indicate that the proposed fuzzy controllers rapidly follow the desired depth without steady-state error although the desired depth was given in one step, and show robustness properties against changes in the parameters such as the change of the towing sped. Especially, a modified rule shows smaller depth fluctuations and faster setting times than those obtained by a field oriented rule.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.2
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• pp.142-152
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• 1995

The combined bottom trawl and hydroacoustic survey was conducted by using the training ship Oshoro Maru belong to Hokkaido University in November 1989-1992 and the training ship Nagasaki Maru belong to Nagasaki University in April 1994 in the East China Sea, respectively. The aim of the investigations was to collect the target strength data of fish school in relation to the biomass estimation of fish in the survey area. The hydroacoustic survey was performed by using the scientific echo sounder system operating at three frequencies of 25, 50 and 100kHz with a microcomputer-based echo integrator. Fish samples were collected by bottom trawling and during the trawl surveys, the openings of otter board and net mouth were measured. The target strength of fish school was estimated from the relationship between the volume back scattering strength for the depth strata of bottom trawling and the weight per unit volume of trawl catches. A portion of the trawl catches preserved in frozon condition on board, the target strength measurements for the defrosted samples of ten species were conducted in the laboratory tank, and the relationship between target strength and fish weight was examined. In order to investigate the effect of swimbladder on target strength, the volume of the swimbladder of white croaker, Argyrosomus argentatus, sampled by bottom trawling was measured by directly removing the gas in the swimbladder with a syringe on board. The results obtained can be summarized as follows: 1.The relationship between the mean volume back scattering strength (, dB) for the depth strata of trawl hauls and the weight(C, $kg/\textrm{m}^3$) per unit volume of trawl catches were expressed by the following equations : 25kHz : = - 29.8+10Log(C) 50kHz : = - 32.4+10Log(C) 100kHz : = - 31.7+10Log(C) The mean target strength estimates for three frequencies of 25, 50 and 100 kHz derived from these equations were -29.8dB/kg, -32.4dB/kg and -31.7dB/kg, respectively. 2. The relationship between target strength and body weight for the fish samples of ten species collected by trawl surveys were expressed by the following equations : 25kHz : TS = - 34.0+10Log($W^{\frac{2}{3}}$) 100kHz : TS = - 37.8+10Log($W^{\frac{2}{3}}$) The mean target strength estimates for two frequencies of 25 and 100 kHz derived from these equations were -34.0dB/kg, -37.8dB/kg, respectively. 3. The representative target strength values for demersal fish populations of the East China Sea at two frequencies of 25 and 100 kHz were estimated to be -31.4dB/kg, -33.8dB/kg, respectively. 4. The ratio of the equivalent radius of swimbladder to body length of white croaker was 0.089 and the volume of swimbladder was estimated to be approximately 10% of total body volume.