• Korean Journal of Remote Sensing
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• v.18 no.5
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• pp.255-261
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• 2002

Strong and coherent radar backscattering signals are observed over oyster sea farms that consist of artificial structures installed on the bottom. We successfully obtained 21 coherent interferograms from 11 JERS-1 SAR data sets even though orbital baselines (up to 2 km) or temporal baselines (up to 1 year) were relatively large. The coherent phases preserved in the sea farms are probably formed by double bouncing from sea surface and the sea farming structures, and consequently they are correlated with tide height (or instantaneous sea level). Phase unwrapping is required to restore the absolute sea level. We show that radar backscattering intensity is roughly correlated with the sea surface height, and utilize the fact to determine the wrapping counts. While the SAR image intensity gives a rough range of absolute sea level, the interferometric phases provide the detailed relative height variations within a limit of $2{\pi}$ (or 15.3 cm) with respect to the sea level at the moment of the master data acquisition. A combined estimation results in an instantaneous sea level. The radar measurements were verified using tide gauge records, and the results yielded a correlation coefficient of 0.96 with an r.m.s. error of 6.0 cm. The results demonstrate that radar interferometry is a promising approach to sea level measurement in the near coastal regions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.5
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• pp.487-493
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• 2009

Available ecological and fishery data of sailfin sandfish, Arctoscopus japonicus, was examined to ascertain its population dynamic parameters in Korean waters. The instantaneous coefficient of total mortality (Z) was estimated to be 1.361/yr, and annual survival rate (S) was 0.256. The estimated instantaneous coefficient of natural mortality (M) was 0.482/yr, and the instantaneous coefficient of fishing mortality (F) for recent years was calculated to be 0.879/yr from Z and M values. Age at first capture was estimated to be 1.958 years. These parameters, in conjunction with catch landings data between 1991 and 2008, were used to estimate annual biomass using a biomass-based cohort analysis. The biomass of A. japonicus was estimated at approximately 7,600 mt in 1991, but since 1994 decreased to below 4,000 mt by 2001. After 2002 they started to increase gradually, and showed the level of more than 5,000 mt in recent years.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.598-606
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• 2013

The blackfin flounder Glyptocephalus stelleri is a commercially important species in the East Sea of Korea, but its catches and biomass have decreased gradually in recent years. This study estimated the optimal catch (acceptable biological catch, ABC) for the effective management of this species by estimating population ecology parameters and the stock biomass of blackfin flounder in the East Sea of Korea. The estimated instantaneous coefficient of total mortality (Z) of blackfin flounder was 1.0542/year, the survival rate (S) was 0.3485, and the instantaneous coefficient of natural mortality (M) was 0.3637/year. From the values of S and M, the instantaneous coefficient of fishing mortality (F) was calculated to be 0.6905/year. The age at first capture was 1.304 years, and the total length was 11.5 cm at that time. On the basis of these parameters, the annual biomass was estimated by a biomass-based cohort analysis using annual catch data in weight by year for 1991-2012 in the East Sea of Korea. The annual biomass peaked in 1997 at about 12,800 mt and then subsequently declined continuously to a level of 10,500 mt in 2004 and to 9,800 mt in 2011 and 2012. The maximum sustainable yield and $F_{0.1}$ were estimated as 3,547 mt and 0.3595/year, respectively. Using these estimations, the ABC was estimated to be 3,571 mt in tier 5, 3,397 mt in tier 4, and 2,622 mt in tier 3.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.234-243
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• 2000

This paper is to study population ecological characteristics, including growth parameters, survival rate, instantaneous coefficients of natural and fishing mortalities, and age at first capture of the soft-shelled clam, Mya japonioa in the intertidal zone of South Sea in Korea. For describing growth of the clam a von Bertalanffy growth model was adopted, The von Bertalanffy growth curve had an additive error structure and the growth parameters estimated from a non-linear regression were SH/sub ∞/=79.83mm, K=0.26, and t/sub 0/= -0.01. Survival rate (S) of the soft-shelled clam was 0.26 (SD=0.02). The instantaneous coefficients of natural mortality (M) was estimated to be 0.78/year and fishing mortality (F) 0.57/year for the soft-shelled clam. The age at first capture (t/sub c/) was estimated as 2.69 year. The mean densities of the soft-shelled clam by bottom type were 3.40 inds./m²(SE=0.18) in the sand, 63.4 inds./m²(SE= 0.53) in the muddy sand, and 0 inds./m2 (SE=0) in the gravelly sand. The mean densities of the soft-shelled clam by 3 different areas were 4.88 inds./m²(SE=0.09), 2.61 inds./m²(SE=0.13), 7.20 inds./m²(SE=0.18), respectively and the biomass of the clam were estimated as 131mt, 121mt, 665mt, respectively. An yield-per-recruit analysis showed that the current yield-per-recruit of about 8.30g with F=0.57/year and the age at first capture (t/sub c/) 2.69 year, was lower than the maximum possible yield-per-recruit of 9.60g. Fixing to at the current level and increased fishing intensity (F) could produce an increase in the predicted yield-per-recruit from 8.30g to about 9.40. However, estimated yield-per-recruit increased to 1.30g by decreasing to from the current age (2.69 year) to age two with F fixed at the current level. Yield-per-recruit was estimated under harvest strategies based on F/sub max/ and F/sub 0.1/.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.448-453
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• 2015

This study was performed to estimate biomass and to provide management plan through population ecological characteristics, including survival rate, instantaneous coefficient of natural and fishing mortalities, and age at first capture of Flathead grey mullet, Mugil cephalus, in the coastal waters of Yeosu. Survival rate (S) of the flathead grey mullet was 3.671. The instantaneous coefficients of natural mortality (M) and fishing mortality (F) was estimated to be 0.325/year, 0.962/year for flathead grey mullet. Also fist capure age of flathead grey mullet was 3.61year. The current biomass of the flathead grey mullet in the study area was estimated to be 19.6 M/T and $F_{0.1}$ and $F_{40%}$ were estimated 0.340/year, 0.225/year. For the stock assessment result, flathead grey mullet was not overfished but overfishing.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.721-729
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• 2022

We investigated the ecological characteristics and biomass of white croaker Pennahia argentata population in the South Sea of Korea using catch data from Danish seins fishery and biological data from 2018 to 2020. Survival rate (S), which was estimated using Pauly method (1984) was 0.361 per year, and the instantaneous coefficient of total mortality (Z) was 1.019 per year. The instantaneous coefficient of natural mortality (M) and that of fishing mortality (F) were estimated as 0.351 and 0.668 per year, respectively. At first capture, age was estimated to be 1.19 years and length at this age was 18.7cm. The annual biomass was estimated with a biomass-based cohort analysis using annual catch data between 1997-2020 in Korean water. The biomass of the white croaker declined sharply from 4,000 tons in 1999 to the lowest level of approximately 1,000 tons in 2004. Post 2004, the biomass started to increase gradually and reached approximately 7,000 tons. The amount of resources was 35.7%, 34.8%, and 16.5% at age one, two, and three years, respectively, and 86.9% of all captured white croaker individuals belonged to the age group of 1-3 years.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.3
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• pp.209-221
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• 2002

In the present paper, a method which enhances the circulation of harbor waters by using wave energy was investigated. The overflow levee was selected as a coastal structure helping the harbor circulation, and was applied to Jeju-outer-port site so as to estimate its effectiveness quantitatively in probabilistic point of view. It was assumed that sea water influx rate through the overflow levee into the harbor depended upon wave height and tidal level and a functional relationship among them was calculated using the results of hydraulic experiment. The probability distribution of water influx could be obtained from hindcasted wave data and measured tidal elevations at Jeju harbor. The Gamma distribution was appeared to best fit the estimated influx distribution, and the optimal location of the levee was discussed. Finally, water quality purification effect was investigated by computing the contaminant material dispersion according to whether the levee was or not.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.272-277
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• 1998

Filtering rates of two farming ascidians Styela clava and S. plicata, and of a farming mussel Mytilus edulis were experimentally investigated with reference to effects of water temperature and size. Absorptiometric determinations of filtering rates were carried out in a closed system with experimental animals being decreased indicate dyes neutral red. Optical density (OD) of 440 nm in path length 22 mm cell used as the indication of food particles absorption was appeared directly in proportion with the concentration of neutral red dyes. The filtering rate F is calculated by Kim's equation $F\;=\;V(1-e^{-z})$, where V is the water volume ($\ell$) in the experimental jar, and Z is the decreasing coefficient of OD as meaning of instantaneous removal speed as In $C_t\;=\;In\;C_{o}-Z{\cdot}t$, in this formula $C_t$ is OD at the time t. Filtering rate of S. clava increased as exponential function with increasing temperature while not over critical limit, and the critical temperature for filtering rate was assumed to be between $28^{\circ}C$ and $29^{\circ}C$. In case of S. plicata, the critical temperature was to be below $13^{\circ}C$, and through the temperature range $15\~25^{\circ}C$ appeared a little difference in level even though with significant. M. edulis was not appear any significant effects by water temperature less than $29^{\circ}C$. The model formula derived from the results is as below, where F is filtering rate (${\ell}/hr/animal$), T is water temperature ($^{\circ}C$), and DW is dry meat weight (g) of experimental animal. $$S.\;Clava;\;F\;=\;e xp\;(0.119\;T-4.540)\;(DW)^{0.6745},\;T<29^{\circ}C$$) $$S.\;plicata;\;F\;=\;e xp\;(A_t)\;(DW)^{0.5675},\;(13^{\circ}C $$[A_t =-8.56+0.6805\;T-0.0153\;T^2]$$ $$M.\;edulis;\;F\;=\;0.3844\;(DW)^{0.4952},\;<29^{\circ}C$$)