• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.169-175
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• 2004

In order to examine the mesh selectivity and optimum mesh size of gill nets for croaker, Milichthys miiuy, the field experiments were carried out during Aug. 10 to 14, 2002 and Aug. 10 to 17, 2003 at the caostal area of Imja-Do, Shinan, Jeonnam province. The experimental fishing gears were used in two set of gill nets, which one set was consisted of 12 sheets of gill nets, and each set was connected alternatively 4 different sheets that were 129mm, 135mm, 144mm and 150mm in mesh size. The analysis of mesh selectivity curve was done by Kitahara's method. The results obtained are summerized as follows : 1. The total number of catch by the experimental fishing of gill nets for croaker was 719, and it was consisted of 526 croakers (73.1%), 168 blue crabs (23.4%), 17 harvest fishes (2.4%) and 8 other fishes (1.1%). 2. The value of maximum 1/m on the mesh selectivity curve was estimated at 6.91. 3. The value of 1/m on the 50% selection range was estimated at 5.62${\sim}$80.3, and the selection width was 2.41. 4. The optimum mesh size of gill nets for croaker was estimated 142mm, and the 50% selection range of total length of croaker was 798${\sim}$1,140mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.176-181
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• 2004

In order to examine the mesh selectivity and optimum mesh size of trap nets for purple shell, Rapane venosa, the field experiments were carried out during Jun. 27 to 29, 2003 at the coastal area of Mal-Do, Kunsan, Jeonbuk province. The experimental fishing gears were used in two set of trap nets, which one set was consisted of 210 trap nets that were coverd with 35mm, 50mm and 65mm in mesh size. The analysis of mesh selectivity curve was done by Kitahara's method. The results obtained are summerized as follows : 1. The total number of catch by the experimental fishing of trap nets for purple shell was 1,682, and it was consisted of 1,268 purple shells (75.4%), 225 Glossaulax reiniana (13.4%), 113 green lings (6.7%) and 76 other fishes (4.5%). 2. The value of maximum 1/m on the mesh selectivity curve was estimated at 1.79. 3. The value of 1/m on the 50% selection range was estimated at 1.24${\sim}$2.72, and the selection width was 1.48.. 4. The optimum mesh size of trap nets for purple shell based on the catch prohibition shell height(50mm) was estimated 40.3mm, and the 50% selection range of shell height of purple shell was 50.0${\sim}$109.6mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.4
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• pp.347-360
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• 2020

In this study, the Bayesian state-space model was used for the stock assessment of the Blackfin flounder. In addition, effective measures for the resource management were presentedwith the analysis on the effectiveness of fisheries management plans. According to the result of the analysis using the Bayesian state-space model, the main biometric value of Blackfin flounder was analyzed as 1,985 tons for maximum sustainable yield (MSY), 23,930 tons for carrying capacity (K), 0.000007765 for catchability coefficient (q) and 0.31 for intrinsic growth (r). Also the evaluation on the biological effect of TAC was done. The result showed that the Blackfin flounder biomass will be kept at 14,637 tons 20 years later given the present TAC volume of 1,761 tons. If the Blackfin flounder TAC volume is set to 1,600 tons, the amount of biomass will increase to 16,252 tons in the future. Lastly, the biological effectiveness of the policy to reduce fishing effort was assessed. The result showed that the Blackfin flounder biomass will be maintained at 13,776 tons if the current fishing efforts (currently hp) level is set and maintained. If the fishing effort is reduced by 20%, it will increase to 17,091 tons in the future. The analysis on the economic effect of TAC showed that NPV will be the lowest at 1,486,410 won in 2038, 20 years after the establishment of 2,500 tons of TAC volume. If the TAC volume is set at 2,000 tons, NPV was estimated to be the highest at 2,206,522,000 won. In addition, the analysis on the economic effect of the policy to reduce the amount of fishing effort found that NPV will be 2,235,592,000 won in 2038, 20 years after maintaining the current level of fishing effort. If the fishing effort is increased by 10%, NPV will be the highest at 2,257,575 won even thoughthe amount of biomass will be reduced.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.6
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• pp.373-380
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• 2012

The sandy beach along the east coast of Korea offers beautiful scenery with high-quality sand for leisure, and is also famous for the white-sand and pine-tree which is an important scenic resource. Furthermore, the sandy beach helps to maintain natural environment of the costal area and functionates as a disaster prevention system against high waves. There are two major value evaluation methods, Travel Cost Method and Contingent Valuation Method, to assess the value of coastal sandy beach. Contingent Valuation Method is considered to be more appropriate for simultaneous evaluation on the usefulness and the uselessness of the beach. But in order to apply Contingent Valuation Method to coastal sandy beach evaluation, close examination and investigation on the potential bias, such as on questionnaires, surveys and replies, are required. In this study, the characteristic of primary amenity of sandy beach users is investigated, in prior to evaluating the usefulness and the uselessness of the beach measured by contingent valuation method. The characteristic of amenity on major sandy beaches on the east coast of Korea is studied and compared by diverse value evaluation methods.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.133-139
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• 2001

In order to obtain fundamental data for estimation of fisheries resource by echo sounder, we carried out the measuring of dorsal aspect Target strengths for rock bream and dusky spinefoot fishes that were caught much around the Jeju Island and in South Sea of Korea. The appropriate equations share the common form. TS=A+20 log L, where TS is the average dorsal aspect target strength in decibels, L is the fish total length in centimeters, and the coefficient A is determined by a least mean squares regression analysis. For rock bream, the result is TS=-72.97+20 log L and, for dusky spinefoot it is TS=-63.16+20 log L And, we have investigated the bearing range of maximum dorsal aspect target strength for all of rock bream and dusky spinefoot by the echo sounder with transducer of which frequency is 200kHz. They are $-12^\circ$-$-21^\circ$and $-1^\circ$--8 espectively, when the fishes is swimming down to the bottom. The maximum dorsal target strengths are -41.50dB at -18 or rock bream and -30.69dB at $-6^\circ$for dusky spinefoot.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.2
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• pp.128-136
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• 2012

Hybrid surveys using hydroacoustic and fish sampling gears such as trammel net, trap were conducted to investigate total biomass, distribution and dominant fish species of the demersal fishes in the marine ranching area (MRA) of Jeju. Four surveys were carried out in June, August, October and November using 38kHz quantitative echo sounder. Catch data using trammel net and trap were used to calculate biomass and to examine dominant fish species. Fish schools were mainly detected in the waters of 20 meters below and around Chagwido waters. By the result of fishing experiments, fish species living in MRA of Jeju were about 40 species, dominant fish species of a detectable fish such as Family Sparidae and Family Monacanthidae etc. were identified 59.4~68.8% of total biomass. Based on the hydroacoustic data, fish length-weight function and target strength information, mean density of the demersal fish estimated were as follows; 0.88g/$m^2$ on June, 1.12g/$m^2$ on August, 1.35g/$m^2$ on October and 1.18g/$m^2$ on November. An estimated average biomass in MRA of Jeju was founded 20.5 tons in 2007, 20.6 tons in 2008, 23.0 tons in 2009, 25.9 tons in 2010. The results showed that biomass of MRA is getting increased slowly. Therefore the hybrid survey method using hydroacoustic and fish sampling gears is assured an effective biomass survey in the waters of mixed species.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.4
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• pp.248-262
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• 2005

The purpose of this study was to identify the state of demersal fish resource catch by small trawlers, which live in the southern waters off Goheung. We investigated the results of catch of sample fishing vessels, and performed fishing experiments using the actual fishing operation vessels from early November in 2002 till end of October in 2003. The daily amount of catch per vessel of the 35 small trawlers selected as sample vessels was the highest in summer seasons(June and July) as 70kg and the lowest in winter seasons(January and February) as 45kg and Octopus minor occupied as 17 to 30kg nearly 30% of the total catch. Additionally the catch of Octopus minor per vessel, per dragging hour ranges 3 to 6kg, which is the highest in March and June and the low in January to February, April to May and September. In the fishing experiments using small trawler, during the study period, a total of 75 fish species were collected. The number of individuals by species consisted 58.2% in Shrimps, 17.8% in Fish, 2.3% in Cephalopod. Of these, Parapenaeopsis tenella was the highest in 29.2%, Squilla oratoria and Crangon hakodatel was 14.6% respectively and Octopus minor was 0.2% of the total number of individuals. As far as the appearance number of individuals by month was concerned, February was the highest and then May, April and June followed in order, and October showed the lowest. Additionally the monthly catch per dragging was the lowest in December to January as 20kg and the highest in July as 160kg. Specially, Octopus minor was caught throughout the year regardless of season and the catch was the highest at the period from March to June. When looking into the body mean length of dominant fishes caught, we could observe the followings; Trachurus japonicus 8.9cm, Cynoglossus robustus 10.8cm, Muraenesox cinereus 15.3cm, Setipinna taty 10.3cm, Amblchaeturichfhys hexanema 9.3 cm and Collichthys niveatus 8.9cm, most of which were in their immaturity when they were caught.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.221-234
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• 2020

We occur together with telluride minerals. Fluid inclusions in the euhedral quartz crystals are mainly aqueous liquid-rich inclusions, which have salinities about 0.18-2.24 wt% NaCl equivalent. Some quartz vein contains aqueous vapor-rich inclusions as well. Homogenization temperatures of the assemblages of the liquid-rich inclusions are about 141-384 ℃, and the temperatures are lower at the shallower vein samples. In the high Au-Ag grade depth intervals, relatively deeper fluids have relatively higher salinities and homogenization temperatures, while shallower fluids show somewhat wider ranges. These might indicate that the deep Au-Ag bearing hydrothermal fluids at the Moisan area experienced phase separation as well as mixing with meteoric water by decreasing pressure. Au-Ag precipitation in the Moisan deposit is not associated with pyrite, but pyrite include Au-Ag bearing phase as an inclusion, which might possibly be tellurides or electrum. Au/Ag ratios in the Au-Ag bearing phase do not change with different depth.

• Applied Microscopy
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• v.40 no.2
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• pp.117-123
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• 2010

This study has examined experimentally the Beer's law which is a precondition for quantitative electron tomography. We used carbon support film and latex spheres, which have similar absorption coefficients with biological samples, as the test samples to take a tilt-series of images for electron tomography. First, the 3D information of carbon film and latex spheres was obtained by electron tomography. Then, the regression analysis on the relationship between the intensities of the incident and the transmitted beams in a tilt series was carried out to examine the Beer's law. The regression results with RMS error of 0.976 show the linear intensity variations of the transmitted beam as the tilt angles were increased. In addition, the relative absorption coefficients of carbon support film and latex spheres calculated experimentally through the Beer's law were 1.71 (5) and 2.67 (6)/${\mu}m$, respectively. The absorption coefficients remained constant within a full tilt range. Therefore, it is expected that quantitative electron tomography could be performed for biological samples by applying Beer's law provided the exact intensity of incident beam can be obtained under the thoroughly controlled experimental conditions.

• Ocean and Polar Research
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• v.40 no.4
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• pp.237-247
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• 2018

This study aims to estimate optimal harvests, fishing efforts, and stock levels of hairtail harvested by the large pair bottom trawl, the large otter trawl, the large purse seine, the offshore long line, and the offshore angling fisheries by using the surplus production models and the current value Hamiltonian method. Processes of this study are as follows. First of all, this study estimates the standardized fishing efforts regarding the harvesting of the hairtail by the above five fishing gears based on the general linear model developed by Gavaris. Secondly, this study estimates environmental carrying capacity (k), intrinsic growth rate (r), and catchability coefficient (q) by applying the Clarke Yoshimoto Pooley (CY&P) model among various surplus production models. Thirdly, this study estimates the optimal harvests, fishing efforts, and stock levels regarding the hairtail by the current value Hamiltonian method, including the average landing price, the average unit cost, and the social discount rate. Finally, this study attempts a sensitivity analysis to figure out changes in optimal harvests, fishing efforts, and stock levels due to changes in the average landing price and the average unit cost. As results induced by the current value Hamiltonian method, the optimal harvests, fishing efforts, and stock levels regarding the hairtail caught by several fishing gears were estimated as 33,133 tons, 901,080 horse power, and 79,877 tons, respectively. In addition, from the results of the sensitivity analysis, first of all, if the average landing price of the hairtail constantly increases, the optimal harvests of it increase at a decreasing rate, and then harvests finally slightly decrease as a result of decreases in stock levels. Secondly, if the average unit cost of fishing efforts continuously increases, the optimal fishing efforts decreases, but optimal stock levels increase. Optimal harvests start climbing and then decrease continuously due to increases in the average unit cost. In summary, this study suggests that the optimal harvests (33,133 tons) were larger than actual harvests (25,133 tons), but the optimal fishing efforts (901,080 horse power) were much less than estimated standardized fishing efforts (1,277,284 horse power), corresponding to the average of the recent three years (2014-2016). This result implies that the hairtail has been inefficiently harvested and recently overfished due to excessive fishing efforts. Efficient management and conservation policies on stock levels need to be urgently implemented. Some appropriate strategies would be to include the hairtail in the Korean TAC species or to extend the closed fishing season for this species.