• Fisheries and Aquatic Sciences
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• 제17권1호
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• pp.145-153
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• 2014

The motion of the otter board on a trawl can affect the motion of trawl nets, and the motion of the codend can affect fish selectivity. Preliminary measurements of the tilt of bottom trawl gear were carried out to compare the tilts of the otter board and codend. The tilt of the otter board was measured by Vector and tilt at 1.5 m anterior to the end of the codend, and the middle upper panel was measured with a micro-DST-tilt logger. Tilt data such as yaw, pitch, and roll were analyzed by the fast Fourier transformation method and global wavelet and event analyses for the period or amplitude. The mean period ${\pm}$ standard deviation of the tilt in the otter board, $(5-6){\pm}2s$, was similar to the period of the codend, $(4-6){\pm}(2-3)s$, whereas the amplitude of the codend was greater than that of the otter board. The yaw and pitch periods were not significantly different between the otter board and codend, but roll was different. Furthermore, the tilt period frequencies of the otter board and codend were not significantly different. Accordingly, the tilt motion of the codend was mostly related to the tilt of the otter board.

• 수산해양기술연구
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• 제51권1호
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• pp.26-34
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• 2015

The angle of attack of a cambered otter board in a bottom trawl was estimated using a three-dimensional semi-analytic treatment of a towing cable (warp) system that was applied to the field experiments of a bottom trawl obtained by the Scanmar system. The equilibrium condition of the horizontal component and vertical component of forces was used to the three forces acting on the otter board in the horizontal plane. Those forces were the force on the warp at the bracket, hydrodynamic lift and drag forces on the otter board and the force on the hand rope attached just behind the otter board. Also the equilibrium of moment about the front edge of the otter board was used to find out the angle of attack of the cambered otter board. When the warp length was 120m and 180m long and the towing speed was between 1.23 and 1.90 m/s, the estimated angle of attack of the cambered otter board was ranged between $26.1^{\circ}$ and $29.6^{\circ}$, respectively, though the maximum lift force was at the angle of attack $22.6^{\circ}$. The angle of attack of the otter board was tended to increase weakly with the longer length of warp (180 m) at the same towing speed in the experiment.

• 수산해양기술연구
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• 제22권4호
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• pp.41-48
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• 1986

To investigate the midwater trawl gear available for the Korean near sea trawlers, the authors carried out a field experiment on the attitude and the opening efficiency of the otter board with the Pusan 404 (160GT, 750ps), a training ship of National Fisheries University of Pusan. The experimental trawl gear was designed to be operable by the ship and the otter board was made of single iron plate with 12% camber ratio. The special-prepared potentiometric angle detector was used for determining the attitude, and the 50 KHz fish finder for the opening between the otter boards. The results obtained can be summarized as follows: 1. The angle of attack varied by moving the towing point on the towing plate of the otter board. It showed 33 to 36 degrees when the point was set at the outmost position, 25 to 31 degrees at the middle position and 19 to 30 degrees at the inmost position, with a decreasing tendency according to the increase of towing speed in each cases. 2. The heel of the otter board always occured inwards, increasing slightly according to the increase of towing speed. 3. The tilt of the otter board always occured outwards, increasing slightly according to the move of the towing point inwards, and decreasing slightly according to the increase of towing speed. 4. The opening between otter boards showed the largest value when the towing point was set at the outmost position.

• 수산해양교육연구
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• 제16권1호
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• pp.124-141
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• 2004

This study focuses on the off-shore trawl fishery, specifically on its restructuring and new regulations governing its operation since the 1990s. This fishery has an important role in terms of fishing capacity and production amount and is dependent on close diplomatic relations with adjacent fishing countries. The off-shore trawl fishery has been shrinking since the 1990s. In addition to a decrease in stock and an increase in imports, there are vessel buyback programs and a decrease in fishing grounds related to a tri-lateral agreement among Korea, China and Japan which have sped up the shrinking of the fishery. In this processing, costs exceed the increase of revenue. Excess investments in fishing gear and salary for crews have lowered profits in this fishery. Considering the above, the off-shore otter trawl fishery should stop increases in production and restructure the fishery by coordinating fishing gear restrictions and fishing areas, and down-sizing management capacity.

• 수산해양기술연구
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• 제22권4호
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• pp.49-55
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• 1986

The authors carried out an experiment to determine the horizontal opening of the mid water trawl gear, which is the same as was used in the foreward experiment concerned to the attitude and opening efficiency of otter board. The trawl net .used in the experiment was designed to have a square sectional four-seamed body with two three-sepenlted wings. Each wing tip was rigged with a net pendant of 70 m long and the fore ends of the pendants were directly jointed to the otter pendant without inserting hand rope, and a front weight of 200 kg weigh was rigged with in front of the lowest wing tip. To determine the opening between otter boards ani between wing tips, two 50 KHz fish finders were set sideways on the otter board and on the port middle wing tip so as to detect the distance froa the finders to the starboard otter board and to the wing tip respectively, and the informations were transmitted to the indicators onboard the ship through water-tight cables. The results obtained can be summarized as follows: 1. The openings between otter borads were 43-45 m in case of the warp 100 m, 53-55 m in the war;> 150 m and 54-59 m in the warp 200 m. It was increased in linear according to the increase of towin; speed in the range of 1. 1-1. 8 mlscc. 2. The determined values of the openings between otter boards were greater than the estimated values. which were calculated by the opening between warps at the gallows of the ship and the length of tt~ warp, assuming that the warps from the top rollers to the otter boards were straight. The rates of the determined values to the estimated values were 1. 23-11. 0 in case of the warp 100 m, 1. 23-1. 12 in the warp 150 m and 1. 23-1. 15 in the warp 200 m respectively. The rates were almost the same at the slow towing speed of 1. 3 mlscc or so, then the higher the speed, the less the rate, and the longer the warp, the greater the rate. 3. The rates of the openings between otter boards to the total length of net pendant and the net (excluded cod end) showed 43-43% in case of the warp 150-200 m. It was a little smaller than th~ standard. which is 50%. in the common bottom trawl. 4. The determined openings between wing tips were 18-19 m in case of the warp 100m, 21-22 m in the warp 150 rn, They showed that the higher the speed, the greater the openings even though its range was no more than 1 m or so. 5. The rates of openings between otter boards to th~ openings betwee:l wing tips were almost invariably 38%. 6. The rates of openigs b2tween otter boards to the lenth of h~ad rope were 60-65% in cas': of th~ warp lOa-150m. It were much larg2r than th~ standard. which is 50%. in the common botto:n trawl.

• 한국수산과학회지
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• 제34권3호
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• pp.238-244
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• 2001

중층트롤 어구의 유체저항을 구하거나 전개판의 간격을 구하는 것은 어구설계나 어로작업에 유용하다. 본 논문에서는 끌줄에 관해 신장을 포함하여 간이해석적 (semi-analytic)으로 푼 3차원해석을 이용하여 중층트롤 어구의 끌줄에 적용시키고, 줄의 형상에 대해 기존의 직선이라는 가정은 실제로 이루는 곡선과는 차이가 있기에, 여기서는 줄의 형상을 곡선 형태로 도입하였는데, 날개그물 끝에서 후릿줄, 뜸$\cdot$발줄 및 (자루그물의) 힘줄에 미치는 세 힘의 합력을 역학적으로 고려하여 어구의 유체저항을 구한 방법을 나타낸 것으로서. 이때 전개판 (OB) 뒤쪽의 후릿줄 (hand rope), bridle 및 뜸 (발)줄의 형상을 곡선인 $y_{r}=Ax_{r}^{B}$의 형태 (B=2이면 포물선 (parabola)임)로 가정하였다. 기존의 중층트롤의 실험자료에서 끌줄의 길이가 100m인 경우에 예망속도의 변화에 따른 여러가지 측정값을 이용하여 트롤어구의 유체저항을 구하는 새로운 방법을 제시하였는데, 10매로 구성된 망지의 유체저항 ($R_{n}(kg)$)과 유속 (V)과의 관계는$1.34 범위에서 $R_{n}=1204.6\;V_{(m/s)}^{1.99}$ 관계가 있었다. 여기에서 제안한 방법을 이용하면 트롤어구의 그물만의 유체저항을 직접적으로 구할 수 있다.

• 한국어류학회지
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• 제23권3호
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• pp.187-197
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• 2011

울진과 후포 연안의 수심 20~50m에서 2002년 계절별로 otter trawl을 이용하여 어류를 채집하여 계절에 종조성 변화와 우점종의 체장조성 분석하였다. 울진 연안에서는 총 20종, 1,927마리, 53,969g의 어류가, 후포 연안에서는 총 23종, 2,762마리, 146,550g의 어류가 채집되었다. 두 조사 지역 모두에서 물메기(Liparis tessellatus), 기름가자미(Glyptocephalus stelleri)와 용가자미 (Cleisthenes pinetorum)가 우점하였으며, 이 3종이 울진 연안 채집 개체수의 70.9%와 생체량의 83.8%를 차지하였고, 후포 연안에서는 각각 90.3%와 70.9%를 차지하였다. 동해 중부 연안에서 정치망이나 자망에는 회유성 부어류들이 주로 채집되어 계절에 다른 변동 폭이 켰으나, 울진-후포 연안의 otter trawl에 채집된 어류는 정착성 저어류들이 전 계절에 우점도가 높아 계절변동이 뚜렷하지 않았다. 우점종인 기름가자미와 용가자미는 약 2~3세어가 주를 이루었으며, 수심에 따른 크기분포에 의하면 이 어류는 자라면서 대륙붕의 수심이 보다 깊은 곳으로 이동하는 것으로 추정된다.

• 한국수산과학회지
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• 제31권5호
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• pp.739-748
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• 1998

1995년 5월, 9월, 11월에 영광군 연안에서 오터트롤로 채집한 수산생물의 종조성을 파악하고, 같은 시기에 주목망에서 채집된 부영생물과 비교하여 영광 근해 수산자원의 특성을 구명하였다. 영광군 연안에서 조사기간 동안 총 73종의 수산생물이 출현하였으며, 이중어류 $63\%$, 두족류 $5\%$, 복족류 $3\%$, 게류 $14\%$, 새우류 $14\%$이었다. 개체수에서 민태 (Johnius grypotus), 그라비새우(Palaemon gravieri), 마루자주새우 (Crangon hakodatei), 참서대 (Cynoglossus joyneri), 눈강달이 (Collichthys niveatus)가 전체의 $64.4\%$를 차지하여 우점하였다. 같은 시기에 같은 정점에서 채집한 주목망에 의한 자료와 비교한 결과, 전반적으로 주목망에는 부영생물이, 오터트롤에는 저서수산생물이 우세하여 채집방법에 따른 종조성의 차이를 보였다.

• 한국어류학회지
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• 제21권4호
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• pp.299-306
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• 2009

Fish fauna in the eastern Yellow Sea was determined using samples collected by an otter trawl from September 1999 to November 2001. The fish consisted of 97 species belonging to 80 genera and 50 families. The major taxa were the Perciformes (40 spp.), Pleuronectiformes (17 spp.), Scorpaeniformes (11 spp.) and Clupeiformes (10 spp.). Larimichthys polyactis, Engraulis japonicus, Liparis tanakai, Pampus echinogaster, Lophius lituron and Collichthys niveatus were predominated in abundance in the study area. The composition of the fish fauna has changed during the last three decades.

• 한국수산과학회지
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• 제50권4호
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• pp.429-436
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• 2017

The seasonal and interannual variations in fish assemblages in the coastal waters off Gijang were examined with an otter trawl from 2015 to 2016. A total of 59 fish species was collected during the study period. The dominant species were Caelorinchus multispinulosus, Clupea pallasii pallasii and Chelidonichthys spinosus. Seasonal changes in fish assemblages appeared to be distinct in the study area. The fish assemblages in summer and autumn were clearly distinguishable from those in other seasons, and the largest numbers of species and individuals were captured in winter and summer, respectively. Because fish assemblages are closely related to changes in water temperature, long-term changes in water temperature can have a significant impact on the productivity of offshore fisheries by changing fish species composition, habitat migration, and growth rate of fish.