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Occurrence of exotic eels in natural waters of South Korea
홍양기,이완옥,김정은,이정호,송미영,박희원 한국통합생물학회 2017 Animal cells and systems Vol.21 No.5
We surveyed the proportion of anguillid eel species inhabiting South Korea natural waters. From September 2014 to August 2015, 429 eels were collected in various habitats for identification using morphological features and DNA-based molecular methods. We found 424 Japanese eels (Anguilla japonica, 98.8%), two European eels (A. anguilla, 0.5%), one American eel (A. rostrata, 0.23%), one tropical eel (A. marmorata, 0.23%), and one short-finned eel (A. bicolor pacifica, 0.23%). Three (A. anguilla, A. rostrata, and A. bicolor pacifica) are exotic species to the natural waters of South Korea; this study is the first record of their distribution in this region. Specifically, A. anguilla was found in the Lake Soyang and Cheongpyeong, while A. rostrata was found only in the Lake Cheongpyeong, and A. bicolor pacifica was found in the Geum River estuary.
홍양기,방인철,성하철,고명훈,김근식 한국통합생물학회 2017 Animal cells and systems Vol.21 No.4
To investigate distribution, habitat characteristics, and current conservation status of the endangered endemic species, rapid small gudgeon Microphysogobio rapidus (Cyprinidae), we surveyed a total of 79 sites from the historic records (20 sites) plus additional sites (59 sites) with good habitat conditions, analyzed their sites, and compared them with historic recorded sites to reveal the factors of extinction threats and causes. We found only eight out of 79 sites in the Nam River areas. The habitats were greatly reduced and restricted compared with the historic sites, which mainly cause from habitat modification, such as various types of river renovations at the main stream and tributary streams of the Nakdong River. The present habitats are higher water temperature and more number of fish species than the absent ones, but conductivity, total nitrogen, and number of weir are lower. In addition, the present sites are lower low velocity at pool and higher mean substrate at pool. From this study, we suggest that maintaining good water quality and preventing anthropogenic impacts greatly aid conservation of the M. rapidus in South Korea.
자호천에 서식하는 멸종위기어류 얼룩새코미꾸리 Koreocobitis naktongensis (Cobitidae)의 서식환경과 번식, 섭식생태
홍양기 ( Yang Ki Hong ),양현 ( Hyun Yang ),방인철 ( In Chul Bang ) 한국어류학회 2011 韓國魚類學會誌 Vol.23 No.3
멸종위기에 처한 우리나라 고유 담수어류인 얼룩새코미꾸리 Koreocobitis naktongensis의 서식환경과 번식, 섭식생태를 연구하기 위해 2010년 3월부터 2011년 6월까지 자호천에서 조사하였다. 본 종은 하천 중?상류에 하상구조가 돌과 자갈이 넓게 깔린 유속 5~10 cm/sec, 수심 50~110 cm인 곳에 주로 서식하였다. 채집한 개체의 성비(♂/♀)는 0.92로 나타났고, 산란시기는 수온이 17~20℃인 5~6월로 추정되었다. 포란수는 평균 22,643 (15,909~30,323)개였으며, 난경은 평균 0.87±0.05mm였다. 주요 먹이생물은 파리 목이었으며, 이 중 72.0%의 상대 중요성 지수값을 나타낸 깔따구류였고 그 다음은 26.9%인 물가파리류였다. Habitat, reproduction and feeding habit of endangered fish Koreocobitis naktongensis from Jaho stream, Gyeongsangbuk-do, Korea were investigated from March 2010 to June 2011. This species inhabits at the upper and middle parts of stream, which were composed of cobbles and pebbles bottom. The current velocities in these microhabitat were 5~10 cm/sec and depth were 50~ 110 cm. The sex ratio of female to male was 1: 0.92. It is presumed that the spawning season is from May to June when water temperatures were 17~20℃. The average number of mature eggs in ovary were about 22,643 (15,909~30,323), mean egg diameter was 0.87±0.05 mm. K. naktongensis fed mainly on Chironomidae (IRI, 72.0%) and Ephydridae (26.9%) of Diptera.
홍양기 ( Yang-ki Hong ),송미영 ( Mi-young Song ),박희원 ( Hee-won Park ),강정하 ( Jung-ha Kang ),이완옥 ( Wan-ok Lee ) 한국어류학회 2017 韓國魚類學會誌 Vol.29 No.2
2014년 9월부터 2015년 8월까지 국내 9개 지점에서 채집된 Anguilla japonica 454개체의 생물학적 특성을 조사한 결과, silvering index (SI) 구분과 GSI의 차이가 큰 pseudo-silver eel 이 소양호에서 2개체 (PS1~PS2)와 금강하구에서 1개체 (PS3)가 확인되었다. Pseudo-silver eel은 외부형태 기준으로는 S2 단계였으나, GSI, 소화관지수 (Gut index) 및 안경지수 (Eye index)에서는 모두 yellow eel 단계인 Y1 및 Y2였고, 생식소 발달단계와 난경에서도 Y2 단계였다. Three pseudo-silver eels (PS1~PS3) were found by analysis of silvering index and biological characteristics of 454 eels, Anguilla japonica, collected from the 9 sites of Korean fresh and brackish waters from September 2014 to August 2015. Two specimens (PS1~PS2) from Lake Soyang and one (PS3) from Geum river estuary were identified as pseudo-silver eel showing a large difference between silvering index and GSI. The external morphology of the pseudo-silver eels were in S2 (late silver eel) stage, but they were classified into Y1 (yellow eel) and Y2 (late yellow eel) stage in GSI, Gut index, Eye index and Y2 stage in gonadal development and mean egg diameter.
홍양기(Y. K. Hong),박상준(S. J. Park),정홍식(H. S. Jung) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.3
Both manufacturing parameters and particles' chemical composition controll coercivity and its distribution of magnetic particles. The coercivity and its distribution are important properties for high density magnetic recording, so these are used as tool for evaluation of reproducibility of magnetic particles. We report in this paper the applications of dM / dH versus H curve, which is derived from magnetic hysteresis loop, to the evaluation of coercivity distribution of magnetic particles and oxidation studies of recording metal particles. The coercivity distribution can be estimated from the full width half maximum (FWHM) and the peak shape of the dM / dH versus H curve. The peak shape of the curve depends upon distribution of particles' coercivity. The peak of dM / dH versus H curve becomes broad and lor is splitted into two or more peaks. It depends on uniformity of particles' coercivity. When the coercivity difference between Ba-Ferrite and γ-Fe₂O₃ is larger than 600 Oe, the peak becomes broad and is consequently splitted into two peaks. Ununiformly substituted Ba-Ferrite particles show broad peak. It is apparent that the analysis of the curve is one of sensitive measuring techniques for determination of coercivity distribution and studies on magnetic properties of substituted Ba - Ferrite and oxidation of magnetic recording metal particles.
고밀도 자기기록용 Ba - Ferrite 분말의 자기적 물성과 입자특성에 미치는 Co+²와 Ti+⁴의 효과
홍양기(Y. K. Hong),박상준(S. J. Park),정홍식(H. S. Jung) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.4
The sites for Fe+³ are partly substituted by Co+² and Ti+⁴ cations to control coercivity of Ba-ferrite particles for use in high density magnetic recording. The substituted Co+² cation has very much different effects on magnetic properties and particle characteristics from that Ti+⁴ cation has. The decrease in the coercivity with the Co+² substitution is attributed to the formation of excessive spinel-block(S-block) in pure Ba-ferrite crystal, while saturation magnetization is increased and the distributions of coercivity and particle size become broad. The substitution with the Ti+⁴ decreases the sauration magnetization, but has less effect on a change in coercivity than the Co+². The Ti+⁴ acts as a nucleation agent in amorphous phase of formulated compound, and consequently particle size and aspect ratio are decreased. Furthermore, the enhancement of substitution of the Co+² for the Fe+³ sites in rhombohedral-block(R-block) by the Ti+⁴ retards the nucleation of spinel phase of Ba-ferrite, which results in uniform magnetic properties of Ba-ferrite particles. It is suggested that the contents of the cations to be substituted for the Fe+³ sites are optimized on the bases of magnetic properties and particle characteristics rather than on the base of electrical charge balance.
입자간 Stacking이 자기기록용 Ba - ferrite 분말의 물성과 분산성에 미치는 영향
홍양기(Y. K. Hong),정홍식(H. S. Jung),박상준(S. J. Park) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.2
It has been known that during magnetic orientation of magnetic Ba-ferrite paint, particle stacking occurs, but also this stacking is found to occur in dry milling process of Ba-ferrite powder in this study. Edge mill was used for dry milling of substituted Ba-ferrite powder. The coercivity of milled Ba-ferrite powder increases linearly with its tap density, and is more dependent on pressure inside a mill than milling time. It is observed by TEM that an increase in the coercivity is attributed to the stacking of particles. A degree of tape's gloss is getting lower with increasing the tap density, which indicates poor dispersibility. The magnetic tape with 1.3 g/㎤ of tap density showed the highest squareness ratio and orientation ratio in the range of 1.1 to 1.7 g/㎤. Excessive dry milling process caused the particles to form clusters, and consequently the dispersibility and orientation became poor.
멸종위기어류 얼룩새코미꾸리 Koreocobitis naktongensis (Cobitidae)의 수조 내 산란행동
홍양기 ( Yang-ki Hong ),양현 ( Hyun Yang ),방인철 ( In-chul Bang ) 한국어류학회 2021 韓國魚類學會誌 Vol.33 No.1
멸종위기에 처한 우리나라 고유 담수어류인 얼룩새코미꾸리 Koreocobitis naktongensis의 호르몬 처리에 의한 산란행동을 관찰하기 위하여 2010년 4월 20~27일까지 산란시기에 성 성숙호르몬 (Ovaprim)을 주사하여 산란행동을 관찰하였다. 산란행동을 분석한 결과 산란 전 행동, 산란행동, 산란 후 행동으로 구분되었다. 산란 전에는 주로 휴식과 유영을 반복하였다. 호르몬 주사 후 평균적으로 11~12시간 경과하면 산란행동을 시작하여 암·수 1 : 1로 1~18회 산란하였고, 수중에서 수컷이 골질반을 이용하여 암컷의 등지느러미 뒷부분의 몸을 원의 형태로 감싸안고 산란이 이루어졌다. 산란 후 행동에서는 특별한 난 보호행동은 보이지 않았으며 산란에 참여하지 않은 개체들이 수정란 일부를 섭식하는 것이 관찰되었다. The Nakdong nose loach, Koreocobitis naktongensis is an endangered freshwater fish endemic to Korea. The spawning behaviour of the K. naktongensis was observed after treating Ovaprim in laboratory aquarium from 20~27 April 2010. The behavioral patterns were categorized into three stages of pre-spawning, spawning and post-spawning behaviors. Before spawning K. naktongensis usually repeated taking a rest and swimming. On average, initial spawning activity started 11 to 12 hours later after injection with Ovaprim. During the spawning period, the number of spawning acts ranged from 1 to 18. The spawning ratio of female to male was 1 : 1. The male embraced the back of the female’s dorsal fin with his lamina circularis. It looked like a complete circle at that time. After spawning, parental care was not observed. Individuals not participating in spawning have been observed to feed on some of the fertilized eggs.