• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.691-699
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• 1997

In order to find out the properties in flow resistance of trawlR=1.5R=1.5\;S\;v^{1.8}\;S\;v^{1.8} nets and the exact expression for the resistance R (kg) under the water flow of velocity v(m/sec), the experimental data on R obtained by other, investigators were pigeonholed into the form of $R=kSv^2$, where $k(kg{\cdot}sec^2/m^4)$ was the resistance coefficient and $S(m^2)$ the wall area of nets, and then k was analyzed by the resistance formular obtained in the previous paper. The analyzation produced the coefficient k expressed as $$k=4.5(\frac{S_n}{S_m})^{1.2}v^{-0.2}$$ in case of bottom trawl nets and as $$k=5.1\lambda^{-0.1}(\frac{S_n}{S_m})^{1.2}v^{-0.2}$$ in midwater trawl nets, where $S_m(m^2)$ was the cross-sectional area of net mouths, $S_n(m^2)$ the area of nets projected to the plane perpendicular to the water flow and $\lambda$ the representitive size of nettings given by ${\pi}d^2/2/sin2\varphi$ (d : twine diameter, 2l: mesh size, $2\varphi$ : angle between two adjacent bars). The value of $S_n/S_m$ could be calculated from the cone-shaped bag nets equal in S with the trawl nets. In the ordinary trawl nets generalized in the method of design, however, the flow resistance R (kg) could be expressed as $$R=1.5\;S\;v^{1.8}$$ in bottom trawl nets and $$R=0.7\;S\;v^{1.8}$$ in midwater trawl nets.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.2
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• pp.147-155
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• 2005

This study was conducted in order to improve the automatic fishing operation system for anchovy boat seine by comparison with the fishing gear geometry and efficiency using the labor saving nets and the combined type net with midwater trawl. Field experiments were carried out to observe the geometry of nets and improve the fishing operation system by catcher boats. The vertical net opening of fore wing net, square, fore bag net and after bag net of the combined type net were varied in the range of 9.9~12.9. 16.2~28.2, 6.8~12.1 and 9.5~15.2m respectively, when the towing speed was 1.0m/sec and the distance between boats were 100m, 200m, 300m. The vertical net opening of the combined type nets was gradually decreased as function of with increasing the distance between catcher boats. Labor saving net which was maintained the net opening and towing depth stable was more suitable for the automatic hauling operation system by improvement of bag net rather than the combined type nets which was impossible in swallow depth and near to anchovy school. 3 boats hauling operation system of the labor saving net was carried out by crane with power block in 2 catcher boats for improvement of hauling operation and pushing equipment of anchovy cooking system in the processing boat for maintain more anchovy in dry frame. From the results of field experiments, 3 boats hauling operation system with power block and improved cooking system was very 3 boats hauling operation system with power block and improved cooking system was very useful and more practical as hauling time 20~35min and No. of fishermen 12~13 in comparison with the traditional system such as hauling time 30~50 min and No. of fishmen 28~38.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.2
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• pp.118-131
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• 1997

An opening efficiency experiment of anchovy boat seine has been carried out using a half size of the ordinary seine to reduce the size of the seine net and to improve the fishing efficiency from field operation. The intervals of towing boats were set at 100, 200 and 300m, and the towing speed, at 0.6, 0.9, and 1.2k't by possible combinations of them. The vertical openings of wing net, inside wing net, bagnet and flapper as well as the spreads of the seine net and the towing tension of the warp were measured, to find out efficient fishing gear and method of the anchovy boat seine. The results obtained are as follows : 1. The vertical opening of the inside wing net ranged from 8.7m to 12.0m at the normal current and from 7.0m to 10.0m at the counter current, and that of the wing net, from 8.4m to 19.8m at the normal current and from 4.9m to 16.3m at the counter current. The vertical opening of the wing net and inside wing net decreased as the towing speed and intervals of the boats increase, from 66% to 16% and from 32% to 18% of the normal opening, respectively. 2. The vertical opening of the fore of bag net ranged from 7.9m to 12.8m at the normal current and from 7.4m to 9.7m at the counter current, and that of the flapper, from 3.4m to 5.1m at the normal current and from 4.4m to 5.1m at the counter current, and that of the flapper, from 3.4m to 5.1m at the normal current and from 4.4m to 5.1m at the counter current. The vertical opening of the bag net was from 98% to 57% of the normal opening and the flapper showed a circular shape and it rose up to the upper layer with a slower towing speed. 3. The vertical opening of the end of the bag net ranged from 7.1m to 9.3m at the normal current and from 7.4m to 8.8m at the counter current. The end of the bag net rose up to the upper layer, This phenomenon was more apparent as the towing speed and the interval of the boats increase. 4. The towing tension of the experimental nets increased from 648kg to 2,716kg at the normal current and from 1,050kg to 6,010kg at the counter current with increasing towing speed. 5. The net depth of the anchovy seine was stable with the higher towing speed and the wider interval of the boats, but it was unstable by rising up to the upper layer with the lower towing speed and the narrower interval of towing boats.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.2
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• pp.87-91
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• 2003

Experimental fishing was carried out to investigate the survival rate of fishes discarded after hauling from the trawl and to develop the fishing gear and method for fisheries management which can improve the survival rate of young fishes escaped from the trawl codend in offshore korean southern sea and off Cheju Island of Korea. The young fishes were bred in fish cage on the board to measure the sustainable survival time for fishes escaped from grid panel and codend. The obtained results are summarized as follows' 1. Japanese flying squid(Todarodes pacjficus), mitra squid(Loligo chinesis), hair-tail( Trichiurus lepturus), john dory(Zeus japonicus), spanish mackerel(Scomberomorus niphonius), redlip croaker (Pseudosciaena polyactis) and blackthroat seaperch(Doederliinia berycoides) were dead instantly after hauling. 2. Survival rate of tiger shark(Galeocerdo cuvier), conger eel (Conger myriaster), red skate (Dasyatis akajei), black scraper(Navodon modestus) and japanese fan lobster(Ibacus ciliatus) might be high after discarding because they survived for long hours in fish cage. 3. Blotched eelpout(Zoarces gili) escaped from the escapement device(grid) was dead within 6 hours in the water tank installed on the board but 97% of tiger shark and 72% of conger eel survived over 72 hours. 4. Red skate escaped from trawl codend was dead within 60 hours in the water tank installed on the board but sustainable survival time of 25% of octopus(Paroctopus dofleini) and 100% of black scraper was over 72 hours. 5. Compared with the survival rate of rosefish(Helicolenus higendorfi) escaped from the escapement device(grid) and trawl codend, all of the rosefish escaped from the grid was dead within 7.2 hours but 8.3% of the rosefish escaped from the codend survived over 72 hours. 6. In comparison with the survival rate of japanese fan lobster survived over 72 hours, survival rate of japanese fan lobster escaped the codend was much higher as 75% than 33% of japanese fan lobster escaped from the grid.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.209-216
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• 2002

How to estimate the shape of trawl net and ropes of a midwater trawl on full scale was described by implementing a three-dimensional semi-analytic treatment of a towing cable system with the field experiments obtained with the Scanmar system. The shape of trawl net from wingend to the beginning of codend was assumed to be of form $\chi$$^2$/ae$^2$+ y$^2$/be$^2$=(z - c)$^2$/c$^2$, and that of the ropes attached behind otter boards be of form yr = $A\chi$rB. In case of warp length 300m long, the volume of trawl net, the ratio of net height to net width at the mouth of the trawl net, and the inclination angle of float rope were estimated according to the change of towing speed. The volume and the distance between wingtips were increased with increasing towing speed. And the inclination angle of float (or ground) rope was slightly decreased with increasing towing speed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.117-123
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• 2001

Anchovy scoop nets, a kind of lift net have been used in the coastal area of Cheju and South sea of Korea. An incandescent lamp(AC 100V, 1kW) is being used as a fishing lamp for gathering anchovy. Fishing lamp was installed at 1m ahead of the prow and 1.5m higher than the water surface. The fishing lamp let fish school rise to the water surface and attract to bag net. Accordingly, a successful anchovy catching depends on controling of fishing lamp. On the study, the distribution of spectral irradiance illumination of incandescent lamp(1kw) and the irradiance efficiency of reflection plate were analyzed and discussed to investigate the ability of fishing lamp which can attract anchovy school effectively. The results obtained are summarized as follows : 1. Around 180% of irradiance efficiency of incandescent lamp was increased by using the reflection plate. The light of lamp was radiated into water with circular shape. 2. The irradiance illumination of incandescent lamp in air was a maximum in wave length of 994nm but it was 690nm at 0.5m and 1.0m of water depth. 3. The relationship between water depth(x) and water illumination(y) of vertical light is represented as follows : y=146.03e supper(-0.37x) 4. The light of incandescent lamp(1kW) pass through much better into vertical direction than horizontal but it was estimated that the light was not able to reach depth of 20m.

• Korean Journal of Environment and Ecology
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• v.30 no.6
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• pp.996-1008
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• 2016

Effects of substrate types (bedrock and boulder habitat) on the community structures of benthic biota (macroalgae, macrobenthos) were monthly examined at Sinheung in Jeju Island, Korea, from Feb. to Nov. 2015. Species diversity of seaweeds and macrobenthos was greater at bedrock sites with 57 and 102 species than at boulder sites having 42 seaweeds and 67 macrobenthos. Average annual biomass of seaweeds was $1,601.13g\;wet\;wt./m^2$ at bedrock site and $448.85g\;wet\;wt./m^2$ at boulder site. Ecklonia cava was the most dominant species, occupying 62.64% ($1,002.93g/m^2$)of total biomass at bedrock. Amphiroa anceps was the most dominant species and subdominant species was Ecklonia cava, Grateloupia angusta, Peyssonnelia capensis and Meristotheca papulosa at boulder site. Density and biomass of macrobenthos were estimated to be $106.9indivi./m^2$ and $871.93g/m^2$, respectively at bedrock site and they were $64.6indivi./m^2$ and $984.28g/m^2$ at boulder site. The dominant macrobenthos species based on biomass were Turbo comutus (36.40%), Astralium haematragum (19.18%) and Anthocidaria crassispina (13.61%) at bedrock site and they were Alveopora japonica (54.13%) and Psammocora profundacella (24.28%) at boulder site.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.2
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• pp.57-62
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• 1978

When fisherman use the boat seine net to catch anchovy, a large noise (drum can, small drum and small gong) is used to scare the anchovy school along the wing nets, and into the bag net were they are caught. We want to know how much of an effect these s:mnds have on forceing the anchovy school towards the bag net. The underwater sounds of ancho\'y, drum can, small drum and small gong were analyzed in the labroatory. The behavioral responeses to the playback sounds of anchovy feeding and sounds of artificial instruments were also investigated. The feeding and artificial sounds of the samples were recorded by a tape recorder through a hydrophone in an anechoic aquarium. The sound intensity level was measured by means of a sound level meter in an anechoic chamber. The frequency and intensity of various sounds were analyzed with an analyzing system consisting of a ~-octave filter set, a high speed level recorder, an amplifier and an oscilloscope. The most successful recording was edited into a 9 to 10 second sound track and was repeated in a sequence of 9 to 10 second intervals. The sequence was then reproduced into an anechoic aquarium through the underwater speaker. The results of investigation are as follows; 1. The frequency of the feeding sound was 63~80Hz, and the pressure level produced was less than 32db. 2. The frequencies of the artificial sounds were 315~ 1,OOOHz, and the pressure levels were 88~95 db in the air. 3. When a hydrophone was placed 70cm below the surface with artificial sounds (drum can, small drum and small gong) produced 1 meter above the surface, the pressure level decreased about 30db. 4. The feeding sound was ineffective in attracting the anchovy, because of interference from ambient noise. 5. The artificial sounds had such a small effect on the anchovy's that they could not be used in ocean fisheries.