• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.43 no.2
• /
• pp.101-115
• /
• 2007

The pound net fishery is very important one in Korean coastal fishery and it need to grasp the characteristics of the net affected by many factors. It is considered that the structure and the shape of the pound net can be changed by the direction and speed of current, wave height, depth and conditions of sea bed. However, most of all, the speed of current and wave height influence more upon the pound net than any other factors to deform and flutter. In this study, author carried out the experiments with a model of double one-side pound net made by the similarity law as 1:100 scales at a real experimental area, and additionally the model net experiments were conducted in the circulating water channel in Pukyong National University. The author analyzed the data of transformation of shape and tension of the model pound net to recognize the characteristics of the current and wave acting on it. Regardless of the direction of flow affecting on the fish court net or bag net, the deformed angle and depth to the side panel and bottom of box nets becomes bigger as the wave gets higher and the period of wave is faster. The tension in both upward or downward tends to be changed by the speed of wave. Those value of changes occurred similarly in either fish court net or bag net. Generally, when bag net is located at upward of flow, the value of tension was bigger 10% than any other location or nets. Regardless of the setting direction, the tension of the pound net is increased in proportion to flow speed, wave height and period of wave, and it becomes bigger about 15-30% at upward to flow than downward. Where the flow is upward in the court net, the tension in the wave increased to 37% compared to the one in the flow only in the condition of flow of 0.1-0.3m/s. Where the flow is upward in the bag net, the tension in the wave increased to 52% in the flow of 0.1m/s, and the tension increased to 48% in the flow of 0.2-0.3m/s.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.37 no.3
• /
• pp.223-231
• /
• 2001

For the purpose of providing the basic data on the improved fishing gear and the man power saving, which contribute to enhance fishing efficiency of set net in the coast of Jeju Island, this study executed the test of fish tank by reducing these actual nets by 1/30 and using the manufactured model nets, and observed and interpreted the behaviors of entering and escaping of the schools of mackerel Scomber japonicus, horse mackerel Trachurus japonicus and rabbit fish Siganus fuscescens. Thereby the result is as follows ; 1. After the elapsed time of 60 seconds, in case of rectangular set net, the ratio for entering by a school of fish marked 50% with mackerel, 18% with horse mackerel and 28% with rabbit fish, and in case of pound net, the ratio for entering net by a school of fish marked 70% with mackerel, 60% with horse mackerel and 30% with rabbit fish. 2. After the elapsed time of 60 seconds, in case of rectangular set net, the ratio for escaping by a school of fish marked 70% with mackerel, 40% with horse mackerel and 24% with rabbit fish, and in case of pound net, the ratio for escaping from net by a school of fish marked 0% with mackerel, 0% with horse mackerel and 3% with rabbit fish. 3. After the elapsed time of 60 seconds, in case of rectangular set net, the ratio for remaining by a school of fish marked 30% with mackerel, 60% with horse mackerel and 76% with rabbit fish, and in case of pound net, the ratio for remaining by a school of fish marked 100% with mackerel, 100% with horse mackerel and 97% with rabbit fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.26 no.3
• /
• pp.230-236
• /
• 1990

To examine the behavior of yellow tail Seriola quinqueradiata and of file fish Navodon modestus to set net, the 1/30 scale model net of the actual set net used in the east coast of Korea was made of netting and set in the indoor experimental tank(700cm W$\times$700cm L$\times$100cm D), of which the water depth was kept 70cm. Total length of yellow tail examined were 37~45cm and file fish were 18~21cm. The fishes were released as groups of 3 to 20 individuals. The number of fish entered into the pound net or the bag net, escaped from the net was counted every minute and accumulated for 10minutes to check the ratio entered and the ratio escaped. The result obtained can be summarized as follows: 1. In case of yellow tail, even though the ratio entered into the pound net was not so high, that into the bag net was comparatively high. Traces of the fish swimming were comparatively smooth and both entering into the pound net and escaping from it was easily done. 2. In case of file fish, even though the ratio entered into the pound net was higher than that of yellow tail, that into the bag net was lower than that into the pound net. Traces of the fish swimming were roundly meandered. Entering into the bag net was not so smoothly done, even though that into the playground was smoothly done. 3. Both yellow tail and file fish, the ratio escaped from the bag net was almost0 and that from the pound net was less than 10%.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.40 no.4
• /
• pp.268-281
• /
• 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
• /
• v.41 no.1
• /
• pp.17-26
• /
• 2005

There are several problems in the commercial pound net in the heavy tide ; the breaking and loss of net, steeply variation of net shape and decreasing of fishing efficiency, etc. In order to solve these problems, we introduced method of added sinker used to coastal cultivating cage of Japan and investigated the possibility of application to the Korean pound net. The results are obtained as follows; 1. In case of the upperward flow with fish court net, tension of the frame line was increased about 10${\sim}$25% than that of prototype according to the added sinker from 1.3gf to 5.2gf. The tension of A-type and B-type was similar to the case of the prototype, the tension of C-type and D-type was increased about 10${\sim}$15% than that of prototype. 2. The variation of deformed angle of fish court net was from 0$^{\circ}$ to 70$^{\circ}$ and that of the slope net was from 0$^{\circ}$ to 64$^{\circ}$ and that of the second bag net was from 0$^{\circ}$ to 46$^{\circ}$ and the depth of the second bag net was increased about 10% when the added sinker was changed from 1.3gf to 5.2gf. The depth of the first bag net and the second bag net were decreased about 50% than that of initial depth. 3. For the deformed angle of fish court net according to the attached point of the added sinker, A-type and B-type were decreased about 25% and 10% than the prototype, respectively. C-type was similar to the case of the prototype and D-type was increased about 15% than that of the prototype. The depth of slope net became deep in turn of A-type, B-type, C-type and D-type. For the depth of the second bag net, A-type, B-type, C-type and D-type were increased about 10${\sim}$15% than that of prototype. The depth of the slope net was changed from 0$^{\circ}$ to 63$^{\circ}$ and that of the second bag net was changed from 0${\sim}$44$^{\circ}$ according to the increase of velocity. 4. The optimal weight of added sinker was about 2.6${\sim}$3.6gf and the optimal attached point of added sinker was the case of C-type and D-type.

• The Journal of Fisheries Business Administration
• /
• v.35 no.1
• /
• pp.1-22
• /
• 2004

Since the red grouper stock was initially declared to be overfished by the NMFS in September 2002, the Gulf of Mexico Fishery Management Council must prepare for the red grouper rebuilding plan considering the following alternative management policies: Total Allowable Catch(TAC), 5 - month season closure, 1800 - pound trip limit, and 50 - fathom longline boundary. The first concern the Council has is to evaluate the effects of recommended policies and the second is to analyze the impact of management policies on yellow edge grouper. This is because the fleets harvest red grouper also catch yellowedge grouper, the regulations on red grouper are likely to allow fishing effort to be distributed into yellowedge grouper. Therefore, this study is aimed at evaluating the biological and economic effects of management policies considering simultaneously the impact of red grouper regulations on yellow edge grouper by developing a combined red grouper and yellowedge grouper bioeconomic model. The overall results indicate that management policies for red grouper would adversely affect the yellowedge grouper stock if yellowedge grouper is not protected by its regulations. The TAC policy has the most serious impact on the yellowedge grouper stock, while the 1800 - pound trip limit policy minimizes the reduction in the yellowedge grouper stock. However, the target stock size of red grouper is achieved as well as the largest net present value of returns is gained in the TAC policy.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.15 no.1
• /
• pp.5-16
• /
• 1979

At the holding of live anchovies which will be used as bait for the skipjack fishing, it is necessary to transrer the holding creel to the holding ground from the long distanted fishing ground. Usually, the creel made with net webbing and shaped like pound, was towed with a tow rope fastened to the front fringe or it, when two serious problems were found. The one was that the leading flap or the webbing of creel was drifted backward by the drag and caused to decrease the volume of the creel and made anchovies mortal. The other was that much time were spent to tow creels for long distance with slow speed, whereas to tow fast made anchovies worn out and caused them mortal. To prevent these defect, the authors carried out a model experiment in a circular flowing tank with a 1/15 scale model creel by four different arrangement of towing, and found out two suitable method, then these two methods were experimented in the sea with full rigged creel, and found the most suitable method out. To decrease the interior current speed of the creel even if it was towed fast, the apron which made by the same webbing of the creel body was enclosed the leading flap of creel, when the interior current speed showed the 35 to 40 percent of towing speed, whereas it showed 50 to 55 percent without apron.