• Korean Journal of Ichthyology
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• v.28 no.2
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• pp.72-78
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• 2016

The age and spawning characteristics of Iksookimia pacifica were investigated in this study to provide baseline data for its ecological characteristics in the Bukcheon (stream), Goseong-gun, Gangwon-do, Korea from January to December, 2013. Age groups of I. pacifica (female) estimated by the frequency distribution of total length in the spawning season indicated that the 30~49 mm group is 1 year old, the 50~74 mm group is 2 years old, the 75~99 mm group is 3 years old, the 100~124 mm group is 4 years old, and the 130~160 mm group is $5{\leq}$years old. The sex ratio (♂/♀) was 0.63, and females were 30~60 mm larger than males. The lamina circularis at the base of pectoral fins in males as a secondary sexual character was created at the 13th month after hatching. The spawning season according to the gonadosomatic index (GSI) was July to August (main spawning season in July) with water temperatures of $20{\sim}25^{\circ}C$. The average number of eggs was $2,503{\pm}1,337$ with a diameter of $1.11{\pm}0.04mm$ in mature eggs.

• Korean Journal of Ichthyology
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• v.28 no.2
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• pp.93-99
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• 2016

Spawning period and spawning characteristics of Kichulchoia multifasciata (Pisces: Cobitidae) inhabiting the Yugokcheon (stream) of Nakdonggang (river) were investigated in the area of Segangyo (bridge), Yugok-myeon, Uiryeng-gun, Gyeongsannam-do, Korea from November 2008 to October 2009. The total length of population indicated that 45~55 mm group is one year old, 55~75 mm group is two years old and longer than 75 mm is regarded over three years old in males and 40~55 mm group is one year old, 55~75 mm group is two years old, 75~95 mm group is three years old and longer than 95 mm is considered over four years old in females (January 2009). It has predicted that the spawning period is from May to June (water temperature in the range $21.0{\sim}26.6^{\circ}C$). Sexually matured individuals appeared over the two years old. The number of eggs in the ovaries was 202~747 ($491{\pm}154.0$).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.367-375
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• 2016

Marbled flounder Pseudopleuronectes yokohamae is a commercially important flatfish in the coastal waters of the East Sea off Pohang, Korea. Maturity and spawning dynamics of P. yokohamae were investigated based on samples collected by gill net and long line in the coastal waters off Pohang from January 2013 to December 2014. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), egg diameter, fecundity, and total length at 50% group maturity. We found that the spawning period was December to February, wherein fecundity ranged from 55,760 eggs at 20.40 cm total length (TL) to 1,559,007 eggs at 46.6 cm TL. The relationship between TL and fecundity (F) was F = 0.0017 TL^3.5604 (R² = 0.6984), and F increased with increasing TL. We estimated the TL at 50% group maturity as 27.4 cm for female and 23.5 cm for male P. yokohamae, respectively. The results from this research will aid in the development of policies on season and minimum catch length for sustainable production of P. yokohamae. We propose that it is necessary to conduct long-term ecological monitoring for this species because biological properties such as spawning ecology and growth performance are being affected by climate change.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.107-111
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• 2020

In this study, we examined the maturation and spawning of yellowback seabream Dentex tumifrons using samples collected by monthly bottom trawling in Korean coastal waters from January to December 2018. We analyzed monthly changes in gonadosomatic index (GSI), maturity stage, histology, fecundity, and total length at group maturity. Spawning occurred in May and October. Fecundity varied with total length as F=1.3754TL^3.2664, with a range of 1,220 to 155,625 eggs per female. At group maturity, 50%, 75%, and 97.5% estimates of female total length were 18.4, 20.5, and 25.3 cm, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.67-73
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• 2020

The maturity and spawning of the yellow goosefish Lophius litulon were studied using samples collected monthly from January to December 2018 from the coastal waters of Korea. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), total length (TL) at 50%, 75%, and 97.5% group maturity, egg diameter and fecundity. The spawning period was from January to June. The size of eggs spawned was between 0.30 to 1.28 mm. Fecundity varied between 328,314 to 1,624,783 eggs. The percentage of sexually mature females estimated from a logistic function was over 50% at 48.67 cm TL, 75% at 56.76 cm TL and 97.5% at 74.89 cm TL.

• Journal of Korean Society for Geospatial Information Science
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• v.6 no.1 s.11
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• pp.75-90
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• 1998

In this study, as a method for management of waterquality in stream, we build a database on a environmental information such as a pollution source, a waterquality. And especially, we simulate the BOD concentration which is a index indicate the status of organic pollution in stream. Also This study purposes not only building a database on all sorts of envirnomental data, but also searching, statistic and analysis of the database. The result of this study enables us to see and understand contamination state in stream esaily, so it can help to enhance the attention. Also, we can quickly know study area and the degree of effects when water contamination occurs abruptly. And also, we can compare and know pollution source state and the pollutant load among districts. It is expected to use it as an auxiliary basis when we make a policy about pollutant load reduction, because we can know the extent of the pollution in strean by each a pollution source.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.289-296
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• 2014

A simple analytical approach for stability assessment of underground storage caverns against ground uplift of overburden rock above the rock caverns for high pressurized fluid such as compressed air energy storage (CAES) and compressed natural gas (CNG) was developed. In the developed approach, we assumed that failure plane of the overburden is straight upward to ground surface, and factor of safety can be calculated from a limit equilibrium analysis in terms of this cylindrical shape failure model. The frictional resisting force on the failure plane was estimated by Hoek-Brown strength criterion which replaces with Mohr-Coulomb criterion such that both intact rock strength and rock mass conditions can be considered in the current approach. We carried out a parametric sensitivity analysis of strength parameters under various rock mass conditions and demonstrated that the factor of safety againt ground uplift was more sensitive to Mohr-Coulomb strength criterion rather than Hoek-Brown criterion.

• Korean Journal of Ichthyology
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• v.23 no.2
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• pp.111-118
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• 2011

The maturation and spawning of filefish, Stephanolepis cirrhifer were investigated using samples randomly collected in the East Sea of Korea from August 2009 to July 2010. The total length at 50% group maturity of filefish was estimated to be 11.7 cm. Based on monthly changes in maturity stages and gonadosomatic index (GSI), the spawning period was estimated to be from June to September, and the peak spawning from August to September. The fecundity (F) ranged from 693,981 eggs to 7,383,429 eggs at 23.6 cm between minimum and maximum total length (TL) 13.3 cm and 23.6 cm respectively. The relationship between TL and F was expressed as F=$12.19TL^{4.208}$ ($R^2$=0.727). The sex ratio of male to female was 1 to 0.9.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.296-305
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• 2018

Maturity and spawning of the pointhead flounder, Hippoglossoides pinetorum were investigated on the basis of samples collected in the coastal waters off Gangwon-do, East Sea from January 2012 to December 2013. The average total length of H. pinetorum was 25.0 cm and 21.9 cm for females and males, respectively. The spawning period was from May to July according to monthly changes gonadosomatic index (GSI) and maturity stages. The spawning period in Gangwon-do was delayed relatively to that in Gyeongbuk-do. The mature egg diameter ranged between $300-700{\mu}m$. The relationship between TL and fecundity (F) was F = 63.574 TL - 1471.3 ($R^2=0.7603$), that is, the larger total length, the more fecundity H. pinetorum had. We estimated that the TLs at 50% group maturity were 25.6 cm for females and 19.9 cm for males. The spawning ecology by sea area should be considered efficient resource management for H. pinetorum. Furthermore, it is necessary to study more on the relationships among growth, maturity and water temperature variations in the East Sea.

• Journal of Aquaculture
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• v.11 no.2
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• pp.173-182
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• 1998

The study has been conducted to understand gonadal development and the effects of $17^{\alpha}$-methyltestosterone on sex inversion of the red spotted grouper, Epinephelus akaara. Fish were collected from Deukyand bay in the southern coast of Korea in August, 1996 and then they had been cultivated at the indoor tank until August, 1997. Gonad somatic index (GSI) in the females of both treated and control group began to increase from February when water temperature was rainse again, and reached the maximum value in August, whereas it had decreased from September adn thereafter maintained relatively low value until January. Unlike females, GSI in the male or intersex of treated groups decreased after June. Hepatosomatic index (HSI) of the control group tended to show the relatively low around Autumn, whereas it showed relatively highr value in April and June when the ovary was in the growing stage. Although the treated groups showed relatively higher value of the HSI than the control, hte paterns in monthly variation of HSI were similar to the control. Sexual change of the female grouper to the male was attempted by acceleration with oral administration of $17^{\alpha}$-methyltestosterone at the dose of 0.2 and 0.5mg/kg fish for 120days. Transitional hermaphroditic gonads were observed from the various size of groupers ranging 21.0 to 36.1 cm in total length, while the functional males could be induced from th individuals of 28.8 to 33.5cm in total length. This result indicated that larger groupers than 30cm in total length should be used for sex inversion to maleness with $17^{\alpha}$-methyltestosterone.