• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.2
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• pp.97-106
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• 2018

The objective of this study was to estimate physical properties and fishing performances of net twine with improved PBS copolymer resin (Bio-new), the existing PBS/PBAT blending resin (Bio-old) and commercial Nylon (Nylon). The tensile strength of Bio-new monofilament was equal to Bio-old and the elongation of Bio-new was about 6 % higher than that of Bio-old in wet condition. The physical properties tests were carried out to estimate breaking load and stiffness in dry and wet conditions, respectively. In the results, the breaking load of Nylon netting was the highest whereas the elongation of Bio-new was 1.4 times higher than that of Nylon netting in wet condition. The breaking load of Bio-old netting was about 9.2 % higher than that of Bio-new netting. However, the elongation of the Bio-new netting was about 3% higher than that of Bio-old. The stiffness of the Bio-new compared to Bio-old was improved about 34 % in dry condition and about 32 % in wet condition. The filed experiments of the fishing performance were conducted with three kinds of drift nets with different netting materials in the coastal sea of Jeju. The each experimental drift net made of different materials showed the similar fishing performance. Bio-old drift net yielded less catches of small sized yellow croaker than other drift nets. The netting materials affected the fishing performance and length distribution of catches in the drift nets.

• Analytical Science and Technology
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• v.16 no.2
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• pp.166-173
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• 2003

To determine levels of PCBs in food, beef, pork, chicken, egg, mackerel, yellow croaker, anchovy, common squid and little neck clam were chosen and collected at markets in Seoul, Busan and Kwangju. Among 209 PCB congeners, 7 congeners (#28, #52, #101, #118, #138, #153 and #180) were selected as target compounds that were known as indicator congeners. Samples were homogenized, treated in alkali solution for 1 hour, and extracted with organic solvents. After extraction, extracts were cleaned up by sulfuric acid, purified on silica gel column chromatography, analyzed by dual column-HRGC/ECD and then confirmed by HRGC/MSD. As results, PCBs were detected in fish samples ranged from 0.0002 to 0.001 mg/kg. Both PCB #101 and PCB #118 were the major contributors among 7 congeners.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.359-364
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• 2001

This paper presents case studies on the multi-species fisheries in Korean waters, Multi-species fisheries were divided into two types, that is, multi-species by a single fishery and single species by multiple fisheries. For the case of single species by multiple fisheries, the small yellow croaker stock caught mainly by the Korean pair trawl fishery and the Korean stow net fishery was selected. This approach uses both standardized fishing efforts for the two fisheries by a general linear model and some data for the economic analysis, and then estimates maximum sustainable yield (MSY), maximum economic yield (MEY) and fishing efforts for MSY and MEY, An analysis of interaction aspects between pair trawl and stow net fisheries was carried out to predict the optimal level of fishing effort from the economic point of view, which gives the largest benefits to the two fisheries.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.583-591
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• 2015

The coastal stow net (stow net hereafter) in Korea is one of the major fishing methods for yellow croaker (Larimichthys polyactis), ribbon fish (Trichiurus lepturus), and anchovy (Engraulis japonicus). In terms of energy efficiency, the stow net fishery is more competitive than towing fishing gears such as trawl gears. The fishing vessels in stow net fishery have consumed less fossil fuel and also have had less carbon dioxide emission into the atmosphere. however, the stow net fishery is necessary to be regulated due to its increased output of the fleet. Therefore, it is required for fisheries authorities to manage the fishing capacity or fishing power for the assurance of fishery's sustainability. For fisheries management authorities, it is necessary to quantify data related to fishing capacity and fishing power to deploy fishery policy in a sustainable way. In terms of data for decision-making, Data envelopment analysis (DEA) method was conducted to estimate fishing capacity. Fishing power index (FPI) was also applied to calculate relative fishing power to approach the problem in a quantitative way.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.6
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• pp.629-636
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• 2010

A simple, rapid method for determining amoxicillin (AMO) and ampicillin (AMP) in aquatic products (flatfish, salmon, shrimp, tilapia, and yellow croaker) was evaluated. For quantification, the AMO and AMP ions at m/z 348.9 and 105.9, respectively, were selected. The limit of detection (LOD) and limit of quantification (LOQ) for detecting AMO were 0.09 and $0.25\;{\mu}g/L$, respectively. The respective values for AMP were 0.02 and $0.05\;{\mu}g/L$. After $100\;{\mu}g/L$ AMO treatment, the level decreased 10% after 7 days at $5^{\circ}C$, while it decreased 20% at $25^{\circ}C$. After 7 days, 94.9.100% of $100\;{\mu}g/L$ AMP remained after storage at $5^{\circ}C$, while 62.3.100% remained after storage at $25^{\circ}C$. Using the food code method, the recovery of AMO ranged from 64.1.92.0% and that of AMP from 44.8.86.2%. With a protein centrifugation method, the recovery of AMO ranged from 39.8.87.9% and that of AMP from 78.0.98.1%. With liquid-liquid extraction, the recovery of AMO ranged from 36.5.88.3% and that of AMP from 31.8.75.1%.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.2
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• pp.162-165
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• 2002

To determine changes of heme compounds on lipid oxidation during repeat heating in white muscled fish (yellowfin sole and yellow croaker), myoglobin, metmyoglobin, total iron, nonheme iron and heme iron contents were analysed. Myoglobin content was decreased in the step of repeat heating. Especially, it was decreased the most rapidly roasted at 180$^{\circ}C$ for 20 min in fillet samples. The skinless fillet roasted at the lower temperature resulted in the higher level of metmyoglobin associated with the reduced myoglobin. Regardless of roasted temperature and time, total iron content was not change in contrast of raw meat throughout processing. Nonheme iron content was increased, but heme iron content was decreased during roasted, heated and reheated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.508-516
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• 2021

Although scientist have been reporting recently that changes in ocean environment influence the species composition, movements, and growth of fish in Korea waters. Previous studies on fish vulnerability owing to climate changes are insufficient to explain the effect of fluctuating ocean environments on fisheries ground. In this study, we suggested a method for the assessment of fisheries sensitivity to various factors in ocean environments in Korean waters. To evaluate the fisheries sensitivity, catch data (Chub mackerel, Hairtail, Common squid, small yellow croaker) from National federation of fisheries cooperatives in Korea (1991-2017) and oceanographic data from Korea Ocean Data Center (KODC; 1960-2017) were normalized using the z-score method. Thereafter, the fisheries sensitivity was calculated using the difference between the catch data and the oceanographic data. Finally, the fisheries sensitivity was evaluated based on evaluation grade ratings. Result revealed that in the south sea, variability in catch data was obviously higher than environmental fluctuation (evaluation grade 1), indicating that catch variability in response to environmental change is most sensitive in the south sea among Korean waters in 2017. These results would be helpful for fishery management and policy for sustainable yield in Korean waters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.315-323
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• 2018

Fossil fuel combustion during fishing activities is a major contributor to climate changes in the fishing industry. The Tier1 methodology calculation and on-site continuous measurements of the greenhouse gas were carried out through the use of fuel by the coastal and offshore gillnet (blue crabs and yellow croaker) and trap (small octopus and red snow crab) fishing boats in Korea. The emission comparison results showed that the field measurements are similar to or slightly higher than the Tier1 estimates for coastal gillnet and trap. In offshore gillnet and trap fisheries, Tier1 estimate of greenhouse gases was about $1,644-13,875kg\;CO_2/L$, which was more than the field measurement value. The $CO_2$ emissions factor based on the fuel usage was $2.49-3.2kg\;CO_2/L$ for coastal fisheries and $1.46-2.24kg\;CO_2/L$ for offshore fisheries. Furthermore, GHG emissions per unit catch and the ratio of field measurement and Tier1 emission estimate were investigated. Since the total catch of coastal fish was relatively small, the emission per unit catch in coastal fisheries was four to eight times larger. The results of this study could be used to determine the baseline data for responding to changes in fisheries environment and reducing greenhouse gas emission.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.535-544
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• 2015

Yield per recruit model is the most popular method for fisheries stock assessment. However, stock assessment using yield per recruit model can lead to recruitment overfishing as this model only considers the maximum yield per recruit without spawning biomass for reproduction. For this reason, spawning biomass per recruit model which reveals variations of spawning stock biomass per fishing mortality (F) and age at first capture ($t_c$) is considered as more proper method for stock assessment. There are mainly two methods for spawning biomass per recruit model known as age specific selectivity method and knife-edged selectivity method. In the knife-edged selectivity method, the spawning biomass per recruit has been often calculated using biomass per recruit value by multiplying the maturity ratio of the recruited age. But the maturity ratio in the previous method was not considered properly in previous studies. Therefore, a new method of the knife-edged selectivity model was suggested in this study using a weighted average of the maturity ratio for ages from the first capture to the lifespan. The optimum fishing mortality in terms of $F_{35%}$ which was obtained from the new method was compared to the old method for small yellow croaker stock in Korea. The value of $F_{35%}$ using the new knife-edged selectivity model was 0.302/year and the value using the old model was 0.349/year. However, the value of $F_{35%}$ using the age specific selectivity model was estimated as 0.320/year which was closer to the value from the new knife-edged selectivity model.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.2
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• pp.143-150
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• 1976

A trial has been made to find out a new method of calculating the survival rate of a fish Population utilizing the length composition data and the characteristics of the frequency curve of the length which usually is normal distribution curve. In this paper, a stochastic method is introduced and applied to calculate the survival rate of yellow croaker caught by Korean trawlers in the Yellow Sea and the East China Sea in 1971. The results are as follows : Mean of survival rate 0.46089 Variance 0.03073 Standard deviation 0.17529 95 percent confidence interval 0.36040-0.56138.