• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.2
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• pp.183-193
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• 1995

Assuming that fishing nets are porous structures to suck water into their mouth and then filtrate water out of them, the flow resistance N of nets with wall area S under the velicity v was taken by $R=kSv^2$, and the coefficient k was derived as $$k=c\;Re^{-m}(\frac{S_n}{S_m})n(\frac{S_n}{S})$$ where $R_e$ is the Reynolds' number, $S_m$ the area of net mouth, $S_n$ the total area of net projected to the plane perpendicular to the water flow. Then, the propriety of the above equation and the values of c, m and n were investigated by the experimental results on plane nettings carried out hitherto. The value of c and m were fixed respectively by $240(kg\cdot sec^2/m^4)$ and 0.1 when the representative size on $R_e$ was taken by the ratio k of the volume of bars to the area of meshes, i. e., $$\lambda={\frac{\pi\;d^2}{21\;sin\;2\varphi}$$ where d is the diameter of bars, 21 the mesh size, and 2n the angle between two adjacent bars. The value of n was larger than 1.0 as 1.2 because the wakes occurring at the knots and bars increased the resistance by obstructing the filtration of water through the meshes. In case in which the influence of $R_e$ was negligible, the value of $cR_e\;^{-m}$ became a constant distinguished by the regions of the attack angle $ \theta$ of nettings to the water flow, i. e., 100$(kg\cdot sec^2/m^4)\;in\;45^{\circ}<\theta \leq90^{\circ}\;and\;100(S_m/S)^{0.6}\;(kg\cdot sec^2/m^4)\;in\;0^{\circ}<\theta \leq45^{\circ}$. Thus, the coefficient $k(kg\cdot sec^2/m^4)$ of plane nettings could be obtained by utilizing the above values with $S_m\;and\;S_n$ given respectively by $$S_m=S\;sin\theta$$ and $$S_n=\frac{d}{I}\;\cdot\;\frac{\sqrt{1-cos^2\varphi cos^2\theta}} {sin\varphi\;cos\varphi} \cdot S$$ But, on the occasion of $\theta=0^{\circ}$ k was decided by the roughness of netting surface and so expressed as $$k=9(\frac{d}{I\;cos\varphi})^{0.8}$$ In these results, however, the values of c and m were regarded to be not sufficiently exact because they were obtained from insufficient data and the actual nets had no use for k at $\theta=0^{\circ}$. Therefore, the exact expression of $k(kg\cdotsec^2/m^4)$, for actual nets could De made in the case of no influence of $R_e$ as follows; $$k=100(\frac{S_n}{S_m})^{1.2}\;(\frac{S_m}{S})\;.\;for\;45^{\circ}<\theta \leq90^{\circ}$$, $$k=100(\frac{S_n}{S_m})^{1.2}\;(\frac{S_m}{S})^{1.6}\;.\;for\;0^{\circ}<\theta \leq45^{\circ}$$

• Journal of the Korean Society of Food Culture
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• v.1 no.3
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• pp.183-196
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• 1986

This study was designed to be link in the chain of the investigation on daily life and consciousness of longevous people in Korea, and to investigate the social life and daily life habit in the past of longevous people. The social life and daily life habit were surveyed on 379 subjects (male 121, female 258) of the aged who were above 80 years of age, from June to November in 1985. 1. 'Generally regular' in the rising time and bedtime between 40 and 60 years of longevous people had the highest figures of 81.8% and 63.1%, respectively. The longevous peoples of 59.4% got up by before 6 a.m., and 61.3% of these aged went to bed from 9 to 11 p.m. But there was no significant difference between male and female. 2. Of the occupation engaged in the longest term of longevous people, the self-management (86.3%) included farming, fishing and household affairs was the highest, whereas administrative position, small-scale management and white-collar worker were only 0.8%, 0.8% and 1.8%, respectively. Therefore, their work involved mainly physical labor (heavy 48.5%, light 47.2%), and mental work was only 2.8% of longevous people. It is believed that this fact was deeply related to the educational degree of them. 3. The longevous people of 58.3% retired from the occupation and household affairs abover 70 years of age, and especially 24.3% of them is including the aged above 80 years of age. 4. The longevous people of 57.2% were shared the role in the home after retirement from the occupation and household affairs, whereas 35.9% of them didn't share. Of the way in killing time in case having no role in the home, 'at home'(50.0%) was the highest, and decreased in the order of 'old people's home' (30.9%), 'ill in bed' (10.3%) and 'asylum for the aged' (8.8%). 5. The acquaintance frequency before retirement from the occupation and household affairs of longevous people showed in the order of 'wide' (38.5%), 'common' (38.0%) and 'narrow' (19.0%), and 56.5% of them had the acquaintance after retirement. 6. Only the longevous people of 38.5% had the hobby and recreation activities of 'more than once' after retirement from the occupation and household affairs, but 53.0% of them was none. Of the kinds of hobby and/or recreation, 'TV-watching' (79.2%) was the highest, and decreased in the order of 'talking with grandchild' (54.2 %), 'working at home' (35.4%), 'religion' (25.0%) and 'chess etc.' (18.1%).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.737-747
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• 1999

To estimate biomass and distribution of the Antarctic krill (Euphausia superba), hydroacoustic survey was conducted on board of R/V Yuzhmorgeologiya, which was chartered by Korea Antarctic Research Program (KARP) group from 18 to 21 December 1998, in the northern part of the South Shetland Islands, Antarctic Ocean, The scientific echo sounder (towing body type) used was EK- 500 (SIMRAD, Norway) with echo integrator (BI-500) at 38 kHz frequency and recorded mean backscattering cross-section coefficient (SA) per 1 $mile^2$ of sea surface. Also, Bongo net sampling was carried out to determine the size of krill and CTD (Conductivity, Temperature and Depth) casting to understand physical structure. Water column was divided into 5 layers (22$\~$65 m, 65$\~$115 m, l15$\~$65 m, 165$\~$215 m and 215$\~$315 m) to know vertical distribution of krill biomass. The standard length of krill collected was between 30 mm and 51 mm, and adult krill had single mode (41 mm). Maximum horizontal length of krill patch was about 35 nautical mile and vertical thickness was about 275 m. High density of krill was appeared in frontal area between Circumpolar Deep Water (>$1^{\circ}C$) and very low temperature water mass (< $-0.5^{\circ}C$) that originate from Weddell Sea. According to the results calculated using target strength equation, krill density was totally higher in continental slope and open water areas than in coastal area. In the study area, krill seems to distribute in depth; density was low at first layer ($\={\rho}=17.0\;g/m^2$) and higher at fourth layer ($\={\rho}=40.19\;g/m^2$). The estimated krill biomass at total survey area and water column was about 2.77 million metric ion ($\={\rho}=151.0\;g/m^2$) and coefficient of valiance ( CV, $\%$) was 19.92. The proportions and biomass of krill biomass at each layer were as follows; layer 1 ($11.3\%$, 0.31 million metric ton, CV=16.24), layer 2 ($13.3\%$, 0.37 million metric ton, CV=34.91), layer 3 ($23.7\%$, 0.66 million metric ton, CV=41.5), layer 4 ($26.6\%$, 0.74 million metric ton, CV=27.84) and layer 5 ($25\%$, 0.69 million metric ton, CV= 26.83).

• Journal of the Korean Society of Food Culture
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• v.1 no.2
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• pp.116-126
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• 1986

This study was designed to be a link in the chain of the investigation on daily life and consciousness of longevous people in Korea, and to investigate the regional feature of longevity areas. The daily life and consciousness were investigated on 379 subjects(male 121, female 258) of the aged who were above 80 years of age, from June to November in 1985. This paper is to report the results investigated the longevity rate, distribution, classification and weather of longevity districts, and also the actual conditions such as the functions of daily life and educational degree of longevous people. 1. The number of longevous people in Korea was 171,449 (male 42,842, female 128,607), and the average longevity rate was 0.46% against total population in Korea(male 0.23%, female 0.69%). 2. Of the longevity rates of shi and/or do in Korea, Cheju(1.03%) was the highest among these districts, and decreased in the order of Chonnam(0.79%), Chonbuk(0.66%), Kyongbuk(0.65%) and Kyongnam(0.61%), whereas the large cities such as Inchon(0.22%), Seoul(0.23%), Pusan(0.23%) and Taegu(0.28%) were remarkably lower than districts in seasides and mountains. 3. The districts above 1.0% of longevity rate in Korea showed 17-guns, and the distribution of these districts was 10-guns of Chonnam, 2-guns of Kyongbuk and Kyongnam, and 1-gun of Kyonggi, Cho-nbuk and Cheju, respectively. 4. Of these districts, Pukcheju(1.65%) was the highest, and decreased in the order of Namhae(1.56%), Sungju(1.24%), Posong(1.22%) and Koksong(1.20%). The highest figure(male 0.71%, female 2.51%) was observed in Pukcheju as contrasted with 0.23%(male) and 0.69%(female) of the average longevity rate in Korea. 5. The sex ratio of longevous people in Korea showed the female/male ratio of 3.0. It is, therefore, believed that the longevity rate of female was 3 times higher than that of male. 6. The longevity districts were classified into seven districts in seasides, three districts in isolated islands, and seven rural districts in mountains. 7. The situation of weather in longevity districts was in the range of 11.2 to $14.8^{\circ}C$ at annual average temperature, and 878.5 to 1585.9mm at annual average rainfall. 8. Of the educational degree of longevous people, uneducated(71.5%) was the highest, and followed by the order of village school(15.8%) and above elementary school(4.8%). 9. In the functions of daily life, the aged moving actively(53.0%) was the highest among these longevous people, followed by the aged moving a little(23.5%). Therefore, it is believed that health degree of these longevous peoples by the functions of daily life was very gratifying.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.2
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• pp.105-118
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• 2000

Anchored measurements (12.5 hr) of suspended sediment concentration and other hydrodynamic parameters were carried out at two stations located at the entrance to Hampyung Bay in summer (August 1999). Tidal variations in water temperature and salinity were in the range of 26.0-27.9$^{\circ}C$ and 30.9-31.5, respectively, indicating exchange offshore and offshore water mass. Active tidal mixing processes at the entrance appear to destroy the otherwise vertical stratification in temperature and salinity in spite of strong solar heating in summer. On the contrary, suspended sediment concentrations show a marked stratification with increasing concentrations toward bottom layer. Clastic particles in suspended sediments consist mostly of very fine to fine silt (4-16 ${\mu}$m) with a poorly-sorted value of 14.7-25.9 ${\mu}$m. However, at slack time with less turbulent energy, flocs larger than 40 ${\mu}$m are formed by cohesion and inter-collision of particles, resulting in a higher settling velocity. Strong ebb-dominated and weak flood dominated tidal currents, in the southwestern and the northeastern part, respectively, result in a seaward residual flow of -10${\sim}$-20 cm $s^{-1}$ at station H1 and a bayward residual flow less than 5.0 cm $s^{-1}$ at station H2. However, mean concentration of suspended sediments at station H1 is higher at flood (95.0-144.1 mg $1^{-1}$) than in ebb (75.8-120.9 mg $1^{-1}$). On the contrary, at the station H2, the trend is reversed with higher concentration at the ebb (84.7-158.4 mg $1^{-1}$) than that at the flood (53.0-107.9 mg $1^{-1}$). As a result, seaward net suspended sediment fluxes ($f_{s}$) are calculated to be -1.7 ${\sim}$-$15.610^{3}$ kg $m^{-2}$ $s^{-1}$ through the whole water column. However, the stations H1 and H2 show definitely different values of the flux with higher ones in the former than in the latter. Alternatively, depth-integrated net suspended sediment loads ($\c{Q}_{s}$) for one tidal cycle are also toward the offshore with ranges of 0.37${\times}$$10^{3}$ kg $m^{-1}$ and 0.21${\times}$$10^{3}$ kg $m^{-1}$, at station H1 and H2, respectively. This seaward transport of suspended sediment in summer suggests that summer-time erosion in the Hampyung muddy tidal flats is a rather exceptional phenomenon compared to the general deposition reported for many other tidal flats on the west coast of Korea.

• Journal of Fisheries and Marine Sciences Education
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• v.10 no.2
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• pp.139-161
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• 1998

This thesis includes a study on the legal regulation, the system and formalities on the control of illegal fishing. And the author analyzed the details of the lists of illegal fishing controlled by fishing patrol vessels of Ministry of Maritime Affairs and Fisheries from 1994 to 1996 in adjacent sea area of Korea. The results are summarized as follows ; 1. The fishing patrol vessels controlled total 826 cases in 2,726 days of 292 voyages by 17 vessels in 1994, total 1,086 cases in 3,060 days of 333 voyages by 18 vessels in 1995 and total 933 cases in 3,126 days of 330 voyages by 19 vessels in 1996. 2. The fishing period of illegal fishing was generally concentrated from April to September. But year after year, illegal fishing was scattered throughout the year. 3. The most controlled sea area of illegal fishing was the south central sea area in the sea near Port of Tongyeong. The sea area occupied about 36~51% of totality and the controlled cases were gradually increased every year. The second was the south western sea area in the sea near Port of Yosu. The sea area occupied about 18-27% and the controlled cases were a little bit increased every year. The third was the south eastern sea area in the sea near Pusan. The sea area occupied about 13~23% and the controlled cases were gradually decreased year by year. 4. The most controlled kind of illegal fishing was the small size bottom trawl. This occupied about 81-95% of totality and the controlled cases were gradually increased year by year. The second was the medium size bottom trawl. This occupied about 4-7% and the controlled cases were gradually decreased year by year. The third was the trawl of the coastal sea, this occupied about 2~4% and the controlled cases were a little bit decreased every year. 5. The most controlled address of illegal fishing manager was Pusan city which occupied about 33-51% of totality. The second was Cheonnam which occupied about 24-29%. The third was Kyungnam which occupied about 16~35%. 6. The most controlled violation of regulations was Article 57 of the Fisheries Act which occupied about 56-64% of totality. The second was Article 23 of Protectorate for Fisheries Resources which occupied about 21-36%. And the controlled cases by it were gradually increased every year.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.599-607
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• 1998

To clarify annual reproductive cycle of Korean dark sleeper, Odontobutis platycephala (Iwata et Jeon), we examined the seasonal changes of gonadosomatic index (GSI), the proportional frequency of oocyte development stages in the ovary and the changes of sex steroid hormone levels in blood from December 1995 to November 1997. In July and August, GSI was 0.35 to 0.72 and most oocytes in the ovary were chromatin-nucleolus stage and perinucleolar stage (proportional frequency: $87\%\~96\%$). In September, GSI was 1.20 $\pm$ 0.12, some oocytes in the ovary were yolk vesifle stage (proportional frequency: $22.8\%$) and vitellogenic stage which appeared very rarely(proportional frequency: $2.2\%$). GSI increased gradually from October and reached 4.59± 0.61 to December. During this period, oocytes of vitellogenic stage increased slightly (proportional frequency in December: $22.1\%$). In January, GSI was 4.32 $\pm$ 0.72 but the proportional frequency of oocytes in vitellogenic stage increased (proportional frequency: $51.2\%$). from February, GSI was increased sharply and reached to 10.51 $\pm$ 1.04 in March, the highest value throughout the year and the proportional frequency of oocytes in vitellogenic stage also reached the highest levels (proportional frequency: $60\%$). From April, GSI was gradually decreased and fell down to 1.11 $\pm$ 0.35 in June. During this period, the proportional frequency of mature oocytes was the highest in April (proportional frequency of mature oocyte stage: $40\%$ in April, $12\%$ May, $5\%$ June) throughout the year, and atretic ovarian follicles were appeared. The blood level of estradiol-17$\beta$ ($E_2$), which stimulates the hepatic synthesis and secretion of vitellogenin, was $0.84{\pm}0.20\;ng/m{\ell}$ in August, and thereafter was not changed until December. from January, it increased sharply and reached the highest level of $ 2.85{\pm}0.35\;ng/m{\ell}$ in March throughout the year, but fell to $0.14{\pm}0.02\;ng/m{\ell}$ in July(P<0.05), 17$\alpha$-hydroxprogesterone(17$\alpha$-OHP) was the peak $13.37{\pm}0.52ng/m{\ell}$ in March, but no significant changes in other period(below $3ng/m{\ell}$, P<0.05). 17$\alpha$, 20$\beta$-dihydroxy-4-pregnen-3-one(17$\alpha$, 20$\beta$-P), which was known as the final maturation inducing hormone in teleost, was $0.74{\pm}0.09ng/m{\ell}$ in April and $0.54{\pm}0.07ng/m{\ell}$ in May, but no significant changes in other period (below $0.26\;ng/m{\ell}$, p<0.05). Taken together these results, the annual reproductive cycle of O. platycephala divided into 4 periods as follows: 1) ripe and spawning period from April to June, main spawning period was from April to May, 2) Resting period from July to August, 3) Growing period from September to December, 4) Maturing period from January to March. Moreover, It was showed that the changes of sex steroid hormone in blood played a important roles in the annual reproductive cycle of O. platycephala.