• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.326-336
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• 2003

In order to modify the construction of gizzard shad coastal purse seine net with possible to the laborsaving of fishing operation in the coastal small fishing vessels, the model experiments were carried out on the model nets for several conventional nets using in the field and the experimental nets was manufactured as 1/100 and 1/60 of the full scale net. The results obtained are summarized as follows；1. In the case of the conventional net and reduction rate 75% in conventional net with purse line the fishing efficiency decreased, the lead line was upward for the surface and the pursing depth of pursing line was very shallow to 2∼3m. 2. In the case of the net having maximum depth in center part designed in this study, the length of float and lead line was 60% of conventional net, the depth of net was fixed 20m to selvage line of the both of the end and extend gradually with 50m, 40m, 30m to the center. Among the these net, depth of pursing line was 20∼23m for 50m and 7∼15m for 40m, 30m the depth of net. These results were suitable for interception of fish school in fishing ground, but several problems will be caused by the depth and current of fishing ground.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.2
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• pp.75-81
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• 1989

In this paper, the authors describe on the field experiment of the newly designed actual stow net, standing on the result of the model experiment to examine the performance of the conventional net and the newly designed net, presented in two previous reports of this series. Concurrently the additional experiment to find out the possibility of changing of operating system from the side to the stern was carried out. 1. Fundamental shape of the experimented net was 20 times aslarge asthe newly designed model net. Performance of the net was detected by using two ultrasonic echo sounders: one was set downward at the top-most spreader of the shearing device to detect the opening height of the device from the sea bed, and the other sidewise at the starboard top-most spreader to detect the top-most opening width of the devices. Opening height of the newly designed net showed about 3m smaller than the conventional net at slow current of 0.6m/sec and less but it overcome 1m at speedy current of 0.8m/sec and more. Opening width of the newly designed net was 1.4 times as large as that of the conventional net, ant the front projection area of the newly designed net mouth was estimated as 1.3~1.6 times as large as that of the conventional net. 2. The experiment on the stern operating system was tightly limited by the structure of the ship employed in the experiment, which was a stern trawler of 2275 GT. The ship confronted by the wind with main anchor, while the net was put over the stern slipway and the hauling line of shearing device was operated through the top rollers of gallows. The experiment was very suggestive in the view point to mechanize the operating system, and so to decrease the man power except the following question. The of bow-stern line of ship, and that of net is much different.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2004.10a
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• pp.12-16
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• 2004

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.1
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• pp.9-16
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• 2005

This study was conducted in order to improvement of fishing gear and fishing operating system for anchovy boat seine by labor saving improved nets. Field experiments were carried out observe geometry of nets and fishing operating system by catcher boats. The obtained results are summarized as follows : The Vertical net opening of fore wing net, wing net, inside wing net, square, fore bag net, flapper, after bag net of the labor saving improved net according to the distance between catcher boats were varied in the range of 5.0${\sim}$7.8, 14.4${\sim}$21.1, 16.2${\sim}$21.2, 14.0${\sim}$17.3, 11.7${\sim}$13.9, 5.4${\sim}$6.9, 8.2${\sim}$9.8m respectively, varied in the range of 50${\sim}$78, 25${\sim}$36, 24${\sim}$31, 31${\sim}$38, 61${\sim}$73, 71${\sim}$91, 87${\sim}$104% of the actual ratio of net opening in each part. Labor saving improved net was performed instant net opening in fore wing net and maintained stable net opening and towing depth by means of attached net pendant. Also, it was minimized as net pocket phenomenon leading to guide anchovy for more catch by means of attached body net. The opening in accordance with distance between catcher boats and towing speed. The catch of labor saving improved net was increased than traditional net due to decrement of net resistance by improvement of bag net leading to increasement of towing speed and reduction of escape anchovy as well as improve nets of whole operation system.

• 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.41 no.1
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• pp.27-34
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• 2005

This study was conducted to examine the mesh selecivity and optimum mesh size of spring frame trap for conger eel. Conger myriaster. It was carried out on 25th Sep. 2002 at the coastal sea of Nung-po, Geojedo. The experimental fishing gear was used in five kinds of different mesh size spring frame trap that were 15mm, 20mm, 25mm, 30mm and 35mm, and one plastic pot as control fishing gear that was 6.7mm hole diameter. The mesh size 15mm, 20mm are the current gears, 25mm, 30mm are used in experiment, and 35mm is the legal mesh. These were made 50 traps, respectively. The mesh selectivity curve was analysed by the Kitahara's method(1968) and the optimum mesh size was estimated by relationship between the total length and diameter of conger eel and by the mesh selectivity master curve. The results obtained are summarized follows : 1. The total number of catch by the trap for conger eel was 835, it was consisted of 537 conger eel(64.4), 225 crabs(2639%) and 73 others(8.7%). 2. The value of maximum 1/m on the mesh selectivity curve was estimated at about 23.9. 3. The optimum mesh size of spring frame trap for conger eel was estimated 34.0mm in 50% selection range of the mesh selectivity master curve.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.156-163
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• 2002

In order to development the construction and dimension of fishing gear for gizzard shad coastal purse seine, first of all investigated to the sinking speed and underwater geometry of net, behaviour of fish school to the net during the fishing operation In the field. The results obtained are summarized as follows; 1. Average sinking speed of net was 13cm/sec in bunt, 9.0cm/sec and 9.5cm/sec in 170m and 280m of center, 4.9cm/sec in end wing side, therefore was fastest in start of shooting and decreased gradually during the shooting process. 2. The most of leadline was reached in bottom from the shooting immediately to hauling time and the mean depth of timber bar used equipment for the escaping prevention of fish school was within the 2.7m. 3. The fish school of gizzard shad was appearanced higher density and remained to the most time in bottom than the surface and repeated to vortical movement, and its tendency to distinct in rapid time of tide current. 4. Behaviour of fish school in the net was showed to the vortical movement by sinking and rising immediately with the shooting of net and then divide with the two shape to follow round the wall of net and no patterns straightly movement in the net, and tendency easily catched in fish school of the wall of net. 5. Escaping of fish school in the gap of wing side was to busy after that seting the timber bar, therefore its function for escaping prevention of fish school was very lowed. 6. Escaping behaviour of fish school was differenced with the depth of fishing ground, the above 20m escaped to busy through the below in ledline because the sinking speed of fish school is fast than the net.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.1
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• pp.58-68
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• 2002

The model experiments for the Eastern sea bottom trawl were conducted for the 3 types of ground ropes and 2 types of seabeds to examine drag characteristics according to towing speed. The model net was based on the net of trawler with 750ps and made by 1/78 of a full scale net. This experiments focused on the drags for 3 types of ground rope, the serving wire, the original and the chain types and 2 types of seabeds, mud and sand of bottom. The results obtained are summarized as follows 1. In the case of the sand bottom, the drags by 3 types of ground rope were orderly increased in turn of the chain, the serving wire and the original type. But, in the case of the mud bottom, the drag of the original type is higher than that of the serving wire type and less than the chain type. 2. In the case of the serving wire type of ground rope, the drags by the diameters of ground rope, ø 1.3, ø 1.9, ø 2.6 and ø 3.25 were increased respectively by 23g, 25g, 32g and 42g at the towing speed of 0.4m/s. 3. The drags of ground ropes were increased exponentially in proportion to the towing speed, in the same way in all of three types of ground rope. 4. The ratios of drag of ground rope against that of the trawl net by the type of ground rope at the towing speed of 0.4m/s on the mud bottom were 0.69 in the chain type, 0.64 in the serving wire type and 0.67 in the original type respectively. 5. The Coefficient of drag($C_d$) by type of ground rope according to the towing speed were 10.0~56.7, 3.0~l6.0 and 1.5~8.5 respectively in turn of the chain type, the serving wire type and the original type on the mud bottom, and that on the sand bottom were 10.0~60.0, 3.0~14.0 and 1.2~6.0 respectively In turn of the chain type, the serving wire type and the original type.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.268-281
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• 2004

A study was carried out in order to estimate the deformation of the pound net according to the current by the model test in the circulating water channel. The tension of the frame rope and the variation of net shape were measured to investigate the deforming of the model pound net in the flow. The results are obtained as follows; 1. The experimental equation between tensions (R) of the frame rope and velocity (ν)was found to be R=$19.58v^{1.98}$($r^2$=0.98) in case of the upperward flow with fish court net and R=$26.90v^{1.72}$($r^2$=0.95)at the upperward flow with bag net according to the velocity from 0.0m/s to 0.6m/s, respectively. 2. As the variation of flow speed inside of the model net was gradually decreased according as which is passed through netting panels, in case of the upperward flow with fish court net, the flow speed was about 70% of initial flow speed at 0.1m/s, 60% at 0.2m/s, 50% at 0.3m/s and 40% 0.4~0.6m/s at the measurement point(h) inside of the first bag net, respectively. In case of the upperward flow with bag net, as the flow speed was steeply decreased according as which if passed through the second bag net, it was 30~60% of the initial flow speed and was 20~30% inside of the first bag net and was about 10~20% inside of the inclined passage net. 3. In case of the upperward flow with fish court net, the variation of deformed angle of fish court net was from 0$^{\circ}$ to 70$^{\circ}$and that of inclined passage net was from 0$^{\circ}$ to 63$^{\circ}$and that of the second bag net was from 0$^{\circ}$ to 47$^{\circ}$ . 4. In case of the upperward flow with fish court net, the variation of deformed angle of the second bag net was changed from 0$^{\circ}$ to 70$^{\circ}$and that of the inclined passage net was from 0$^{\circ}$ to 55$^{\circ}$ and that of the fish court net was from 0$^{\circ}$ to 50$^{\circ}$. The depth ratio of the first bag net was changed from 0% to 35% and that of the second bag net was from 0% to 20% and that of the inclined passage net was from 0% to 35%. In the flow speed 0.5m/s, the inclined passage net was raised up to the entry of the bag net and then prevented it more over 90%. 5. To be increased the opening volume of pound net, it needs to attach the added weight outside of the fish court net, inclined passage net and bag net. At the same time, it needs to adjust the tension of the twine for maintenance of the shape.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.1
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• pp.1-11
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• 2018

This study was conducted in order to improve fishing gear for existent net of the anchovy boat seine. Field experiments were performed to observe geometry of nets by catcher boats. When the distances between the two ships were 100, 300, and 500 m, and the speeds of towing nets were 0.6, 0.9, and 1.2 k't, respectively. The vertical opening and actual opening of each part of the existent net was as follows: the middle part of the wing net, 12.9-26.6 m, 19-39%; the entrance of the inside wing net, 23.3-35.3 m, 40-60%; the square and bosom, 18.4-24.2 m, 37-49%; the entrance of the bag net, 19.0-23.3 m, 79-96%; the flapper, 13.2-15.3 m, 142-161%; and the end of the bag net, 13.2-15.7 m, 51-61%. The actual net opening of each part of the existent nets used in this study was lower than that of the design net height, due to the low net height of the wing net and the inside wing net, it limited a range of the net height of the square and bosom. The opening of the entrance of the bag net caused the net pocket shape and inflated some parts of the nets. The tension of towing nets was measured between 4.4 and 11.0 tons, and it is necessary to reduce the structure and improve the structure of the bag net.