Heui-Chun An

A study on vertical distribution observation of giant jellyfish (Nemopilema nomurai) using acoustical and optical methods

A giant jellyfish (Nemopilema nomurai), which is presumed developing in the East China Sea, is recently one of major issues in the Northeast Asia region due to its fatal damage to the fishery. The biomass estimates have generally been conducted by trawl sampling and sighting survey methods. The biological research is also needed to clarify such environmental origin or diurnal migration patterns. While trawl sampling or sighting survey methods are effective to investigate its density estimates in its distributed community of near bottom or surface, they have a problem in investigation on the vertical distribution of jellyfishes. In this case, an echo sounding detection would have an advantage to survey it more extensively and effectively. This trial was conducted to observe the vertical distribution of giant jellyfish, where thermocline strongly formed, during mooring at each station of the East China Sea and southern coastal area using acoustical and optical methods. By the results, they were observed to exit and move at the water column under the thermocline using the optical camera and echo sounder system, and the information was analyzed to find out the acoustical sound scattering characteristics relatives to 120kHz frequency. These results can be utilized effectively to estimate the vertical distribution and biomass of Giant jellyfish with comparing results from trawl sampling and sighting survey methods, hereafter.

The development of basic structure of jellyfish separator system for a trawl net

The purpose of this study is to develop the jellyfish separator system(JSS) for reducing fishery damage bythe increase of jellyfish in the sea area of Korea in summer. First of all, to find the optimum structure of aJSS, six types of JSS in trawl fishery were designed and manufactured, the underwater shape of JSS and theseparating process by JSS were observed in the circulating water channel(CWC). And the field experimentswere carried out in July and September 2004 in the southern sea of Korea. For the moving path of thejellyfish model in the CWC, in case that the model was larger than the mesh size of the separator net, it wasguided toward the lower part of the separator net by the guiding net and discharged through the outlet. Incase that the model was smaller than the mesh size of the separator net, some models which passed throughthe upper part of the guiding net were smaller than the mesh size of the guiding net and discharged throughthe outlet and most of the model which passed through the lower part of the guiding net moved to the cod-end passing through the separator net. According to the field experiment result, the optimum tilt angle ofseparator net was inferred 20that the discharge rate of jellyfish was higher than the other tilt angle ofseparator net and the optimum structure of JSS was inferred GS type(consists of guiding net and separatornet) that the discharge rate of jellyfish was higher than S type(consists of separator net). It was demamded tocarry out more study for the countermeasure to reduce loss of fish.Key words : Trawl, Jellyfish, Separator system, Guiding net, Separator net

Operating Performance of hair-tail angling vessel using the LED and metal halide fishing lamp combination

One of representative Korean fisheries, jigging and angling has 5,700 vessels for squid and hairtail. Hairtail angling is the most typical fishery in Jeju and has an enormous impact on regional economy. However, the price hike in oil and labor costs triggered the necessity of developing a high efficient and energy saving fish luring lamp in recent times. For that reason, this study aimed to analyze the fishing performance of the aircooled LED lamp targeting hairtail angling fishery. The experiment was conducted from September through October in 2009-2011 for a 9.77 ton of fishing vessel setting up 100 lamps. The fishing performance was tested compared with 6 vessels using metal halide lamps in the same waters. As the LED lamp`s performance goes up, different lamps were used in 2008 for 80W, 2009 for 120W and 2011 for 180W respectively. The catch and CPUE of the experimental vessel have gradually increased respectively taking the and place in 2009, the and place in 2010, the and place in 2011 among the 7 vessels. In summary, the LED fishing lamp showed higher fishing performance than comparison groups. It saved 33% of oil consumption and cut down on operating expenses and greenhouse gases emission.

Fishing power estimation of biodegradable traps in the East Sea

For an effective management of fisheries resources, it is very important that to make clean inhabitation environment and to preserve fisheries resources. The material which is mainly used as fishing gear in modern times, is polyethylene, polypropylene, polyamide, etc., chemical fiber. And lost fishing gears which are make of these, occur ghost fishing and ocean pollution. To solve these problem, we development biodegradable fishing trap using the polybutylene succinate (PBS). Developed traps are for red snow crab (Chionoecetes japonicus) and shrimp, major traps in the East Sea, and we carried out fishing research using two kind traps in the coastal sea of Ayajin-port (Goseong) to analysis fishing efficiency of PE trap and PBS trap. As a result for fishing experiment (year 2005-2006) of red snow crab trap, two kind traps were almost the same in catches and length composition. During a experiment, parts of meshes, used for over 1 year, were cut by biodegradation. As a result for fishing experiment (year 2007) of shrimp trap, northern shrimp (Pandalus eous), coonstripe shrimp (Pandalus hypsinotus) and morotoge shrimp (Pandalopsis japonica) were catched, and the almost is northern shrimp. Two kind traps were almost the same in catches and length composition. In accordance with these result, it is recommended that the developed traps are have to commercialized because the fishing powers of PE traps and PBS traps were same. But biodegradation speed is have to controled in consideration of ocean microorganism volume and traps life.

Mesh Selectivity of Durm Net Fish Trap for Elkhorn sculpin(Alcichthys alcicornis) in the Eastern Sea of Korea

The mesh selectivity of the drum net fish trap for elkhorn sculpin(Alcichthys alcicornis) in the estern sea of Korea was described. The selection curve for the elkhorn sculpin caught from the experiments between June 2003 and December 2003 was by SELECT(Share Each Length Class`s Catch Total)model and by Kitahaa`s method to a polynomial equation and two parameter logistic selection curve. The selection curve by SELECT model showed to be equal probability of entrance of the elkhorn sculpin in the large(55mm) and small(20mm) mesh traps by minimum AIC (Akaike Information Criteria). The equation of selectivity curve obtained by Kitahara`s method using a logistic function with least square method was

Species composition and cluster analysis of the communities caught by dredge in relation to tooth spacing and mesh size in the coastal waters of Gangneung, Korea

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The characteristics of the flow field around canvas kite using the CFD

The dredge gear is dragged along the bottom of the sea to catch targeted edible bottom dwelling species. Species composition and ecological index of the catches of dredge were estimated around Gangneung coastal fishing ground by dredge with different mesh size and tooth space from July to December 2013. Eight different types of dredge including four different tooth space (24.7 mm, 29.9 mm, 34.9 mm, 40.1 mm) and four different mesh size(15.5 mm, 32.7 mm, 51.1 mm, 60.0 mm) were used in the experiment. During the experiment, total catches were collected 31 species as sipunculida 1 species, mollusca 13 species, annelida 3 species, arthropoda 8 species, echinodermata 4 species and others 2 species. The dominant genus were mollusca and echinodermata while the dominant species were Megangulus venulosus, Pseudocardium sachalinensis, Schaphechinus brevis. The richness index was ranged 1.29-1.72, evenness index was 0.6-0.65 and diversity index was 1.65-1.83 according to the tooth space and mesh size of dredge. Richness index, diversity index were high at tooth space 34.9 mm dredge and ecological index showed decreasing tendency with the increasing of mesh size of dredge. Cluster and MDS analysis, based on a Bray-Curtis and similarity matrix of fourth root transformed data of number of species and wet weight, showed division into four different groups as four different tooth space (Group A), four different mesh size Group B (51.1 mm, 60.0 mm), Group C (32.7 mm) and Group D (15.5 mm).

The study on the Anchovy`s (Engraulis japonica) reaction to several light colors in a tank

This research aims at establishing the fundamental characteristics of the kite through the analysis of the flow field around various types of kites. The approach of this study were adopted for the analysis; visualization by CFD(computational fluid dynamics). Also, the lift/drag and PIV(particle image velocimetry) tests of kites had been performed in our previous finding. For this situation, models of canvas kite were designed by solidworks(design program) for the CFD test using the same conditions as in the lift/drag tests. And we utilized FloWorks as a CFD analysis program. The results obtained from the above approach are summarized as follows: According to comparison of the measured and analyzed results from mechanical tests, PIV and CFD test, the results of all test were similar. The numerical results of lift-coefficient and drag-coefficient were 5-20% less than those of the tests when attack angle is . In particular, it showed the 20% discrepancy at . The numerical results of the ratio of drag and lift were 8-13% less than those of the tests at and 10% less than those of the tests at . Pressure distribution gradually became stable at . In particular, the rectangular and triangular types had the centre of the high pressure field towards the leading edge and the inverted triangular type had it towards the trailing edge. The increase of the attack angle resulted in the eddy in order of the rectangular, triangular and inverted triangular type. The magnitude of the eddy followed the same order. The effect of edge-eddy was biggest in the triangular type followed by the rectangular and then the inverted triangular type. The action point of dynamic pressure as a function of the attack angle was close to the rear area of the model with the small attack angle, and with large attack angle, the action point was close to the front part of the model.

Catch characteristic and present condition of by-catch & discard of trammel nets fishery in the East Sea

This study was conducted to develop energy-efficient LED lamps with an excellent fishing performance for an anchovy scoop net by comparing the functions of 6 different lamps- incandescent, blue LED, green LED, white LED, yellow LED and red LED lamp. We used incandescent and red LED lamps only for the initial test and then excluded because those showed the lowest herding capacity. According to the result, yellow LED showed lower herding capacity in comparison with the blue, green and white one. Although the herding performance of the blue, green and white LED was similar in almost tests, herding speed to the each light was different. The anchovies were gathered into the blue LED as the speed of 39.88cm/s that was the fastest. Green LED was the second as the speed of 33.28cm/s. White LED was the slowest as the speed of 26.73cm/s. We will have field tests because we found the result that yellow LED`s herding performance was better than green LED`s for 5 seconds comparing after starting in some tests.

Size selectivity of gill net for female snow crab, Chionoecetes opilio

For an effective management of fisheries resources, we need fisheries informations necessary for theestablishment of reasonable fishing effort and TAC distribution. To study the present state of by-catch anddiscard of gill-net fishery in the East Sea, we carried out fishing research using trammel nets in the coastalsea of Susan-port (Yangyang), Jangho-port (Samcheok) and Hupo-port (Uljin). As a result, a total of catchof Susan was 259,172g and that of Hopo was 577,638g. Thus Catch of Susan was 1.49 times more than thatof Hupo considering the number of used fishing gear. And catch of Janho was 7.4 times more than that ofSusan considering the number of experiment. Two methods of by-catch analysis in this study were used, onemethod is standardizing of listed species catching possible in fishing license, another method is regardingcatch species under 1% of total catch as by-catch. As a result of by-catch analysis of two method, by-catchrate of Susan was 6.55% and 5.87% respectively, that of Hupo was 44.70% and 5.24% and that of Janghowas 0.96% and 2.31%. Discard rate of fish in Susan, Hupo and Jangho were 1.59%, 3.42%, 2.23%respectively.Keywords: Fishing capacity, Trammel nets, By-catch, Discard