• Korean Journal of Ichthyology
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• v.19 no.3
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• pp.185-192
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• 2007

The present experiment was carried out to study the effects of light intensity on growth, survival, caudal fin shape, body composition, skin color and blood component of river puffer, Takifugu obscurus. Four light intensities (0, 500, 1,000, 2,000 lx) were tested in duplicates for 60 days. Specific growth rate (SGR), daily feeding rate (FR) and food coefficient (FC) were reduced following to the decrease of light intensity. However in survival rate there was not significantly different among groups. The damage extent of caudal fin was increased in more strong light intensity. In body composition, moisture and crude protein were only significantly difference according to light intensity. In body color, L and a were the highest in 0 lx. In blood analysis, the content of AST, ALT, GLU significantly increased in more powerful the intensity groups. It is concluded that the supplement of low light intensity (e.g. 0 lx) recommended for the commercial scale aquaculture of river puffer in land-based tank without growth and survival retardation.

• Korean Journal of Ichthyology
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• v.30 no.4
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• pp.185-193
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• 2018

From 2017 to 2018, the disease has been monitored at four culturing eel farms in Incheon and Gyeonggi region in Korea. As a result, diseases with gill congestion frequently occurred. This disease occurred regardless of size of eel, but the frequency and cumulative mortality were high in eels within 3 months after stocking. The infected fish showed pathological histopathological features such as intense congestion and dilation in the central venous sinus (CVS) of gill filaments and hemorrhages in liver and kidney. Hexagonal viral particles measuring about 70 nm in diameter was observed in nuclei and cytoplasm of gill vascular endothelial cells. Molecular biologic diagnosis by both PCR and genetic analysis has been revealed that the causative agent of this disease is Japanese eel endothelial cells-infecting virus (JEECV), the cause of viral endothelial cell necrosis of eel (VECNE), which is mainly reported in Japan. This study is the first report on the characteristics of JEECV and VECNE infection in domestic eel farms.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.22-22
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• 2003

로티퍼는 해산어와 담수어뿐만 아니라 식용어와 관상어에 이르기까지 모든 어류의 인공 종묘 생산 과정에서 초기 먹이생물로 이용되고 있는 중요한 동물 플랑크톤이다. 그리고 로티퍼를 초기 자어의 첫 먹이로 사용하는 것을 시작으로 알테미아, 코페포다 또는 초미립자 사료 등을 사용하는 어류 인공종묘 생산 과정에서의 먹이계열이 확립되어 있다. 그러나, 사육하고자 하는 어종에 따라 초기 자어기에서 로티퍼를 섭이하는 시기와 사육 일령별 자어의 로티퍼 포식수를 알 수 있는 정확한 방법이 없다는 이유로 지금까지는 자어의 로티퍼 최초 포식 일령 및 로티퍼 포식수를 개개의 연구자들 나름대로의 방법으로 관찰하여 왔다. 일반적으로 자어가 로티퍼를 포식하였는지의 여부 및 포식수는 자어 소화기내에 존재하는 소화가 진행되기 전의 로티퍼 몸체의 수를 계수하는 방법으로 이루어졌다. 로티퍼의 체내에는 섬모환으로 모은 수중의 먹이 현탁액을 소화기계로 이동시키기 전에 먹이를 잘게 다지고 부수는 기능을 하는 저작기 (trophi)가 존재한다. 그리고 이 저작기는 로티퍼의 종에 따라서 다른 형태를 하고 있는 것으로 알려져 있다. 이 연구에서는 자어가 섭이한 로티퍼는 어류의 소화기내에서 소화가 진행되는 과정에서 로티퍼의 체 구조 중 저작기가 쉽게 소화되기 어렵고 소화기관의 연동 운동에 의해서도 쉽게 그 모양이 손상되지 않는다는 것을 발견하고 이 저작기의 수를 계수하므로서 로티퍼의 최초 섭이 일령 및 일령별 로티퍼 포식수를 계수할 수 있는 방법을 검토하였다. 그 결과, 소화기내의 잔존 로티퍼 몸체만으로 계수 관찰하던 기존 방법에 비교하여 로티퍼의 저작기를 계수하는 방법을 이용할 경우 보다 신뢰도가 높은 결과를 도출할 수 있음을 확인하였다. 경제적 가치의 우수성 때문만은 아니다. 미국은 자국의 대두 생산자들이 생산해 낸 대두를 판매하면서 조성한 자조금을 모아 대두의 생산성을 향상시키기 위한 연구 개발과 국내외 시장을 확대하기 위한 마케팅 활동에 쓰고 있다. 이런 자조 노력은 비단 미국의 대두 농민들에게만 국한된 것이 아니다. 가깝게는 일본의 수산업과 해산어 양식산업의 발전은 중앙 및 지방 정부, 수협과 같은 어민 조합 및 연근해 수산업 종사자들이 출연한 기금을 통해 이루어지고 있음을 지난 8월 북해도의 양식산업을 시찰했을 때 확인할 수 있었던 사실이다. 이제 우리나라도 국민소득 1만불 시대를 넘어 2만불 시대를 열기 위한 청사진을 그릴 만큼 모든 경제의 규모가 확대되었을 뿐 아니라 질적으로 고도화되었다. 우리에게 필요한 것은 성숙된 산업사회에 걸맞는 각 산업 주체들의 의식이다. 한국의 양식산업도 자조 정신을 갖추어 생산성 향상에 초점을 맞춘 양식기술의 개발, 환경 보전을 고려한 양식장 관리 및 소비를 확대하기 위한 유통시스템의 선진화에 스스로 투자를 해야 할 시기에 와 있다.치가 완전히 익은 15일 후에는 무첨가 김치, 0.1%, 0.2% 및 0.3% 고분자 키토산 김치의 젖산균 수는 5.4X107 cfu/g, 3.3X107 cfu/g, 8.6X106 cfu/g 및 2.6X106 cfu/g로 나타났다. 5. 발효가 진행 중에 대장균 군 수가 시간과 더불어 대장균군 수가 모든 구에 있어서 6일까지는 서서히 증가하다가 그 후부터는 대장균 군 수가 감소하였다. 즉, 발효초기에는 모든 구가 2.0X104∼4.0X105 cfu/g이었고, 6일 경에는 8.9X104∼4.5X105 cfu/g로 약간 증가하였으며 15일후에는 키토산 무첨가 김치가 2.0X

• Journal of Life Science
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• v.22 no.6
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• pp.788-793
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• 2012

High concentration of antibiotics has been used to treat the outbreak of edwardsiellosis caused by Edwardsiella tarda in aquaculture. However, not all of the bacteria have been killed with high concentrations of antibiotics treatment by the formation of persister cells with a dormant state. The main objective of this study was to kill persister cell using antibiotics with the addition of natural plant compounds. Antibiotics used in this study consist of 100 mg/ml florfenicol and 100 mg/ml amoxicillin. Ten natural plant compounds with persister cell inhibitor activity to E. coli were obtained from Protein Engineering and Systems Biology Lab. of Sungkyunkwan University. The persister cell inhibition activities of those natural plant compounds were evaluated in test tube. Concentrations of the antibiotics were in the ranges of 25~200 ${\mu}g/ml$. The persister cell formation was observed after 16 hours of culture. Persister cells were killed by antibiotics with natural plant compounds. Among ten natural plant compounds, Gynostemma pentaphyllum, Mallotus japonicus, and Orixa japonica showed persister cell formation inhibition activities. The optimal concentrations of G. pentaphyllum, M. japonicus, and O. japonica for the inhibitor of persister cell formation were 100 ${\mu}g/ml$, 100 ${\mu}g/ml$, and 200 ${\mu}g/ml$, respectively. In vivo study was carried out to evaluate the effect of the antibiotics with natural plant compounds using aquacultural fish, olive flounder, as test animals. G. pentaphyllum, M. japonicus, and O. japonica of 30 ${\mu}g/ml$, 10 ${\mu}g/ml$, and 10 ${\mu}g/ml$ with antibiotics reduced cumulative mortalities, showing the effectiveness of persister cell inhibition.

• Journal of fish pathology
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• v.18 no.2
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• pp.133-146
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• 2005

A bacteriological survey in maricultured fish farms was conducted in Korea from 2002 to 2004. A total number of 166 Vibrio isolates were collected from diseased fishes, including olive flounder (133 isolates), black rock fish (8 isolates), red sea bream (6 isolates), shrimp (5 isolates), black sea bream (4 isolates), abalone (3 isolates) and other fishes (7 isolates). All isolates were phenotypically characterized and then groups were obtained using the traditional biochemical test. Representative isolates of each group were genotypically characterized with sequencing the 16S rRNA genes or 16S-23S intergenic space genes. Above 14 species of Vibrio were identified as V. ichthyoenteri (45 strains), V. alginolyticus (34 strains), V. harveyi (32 strains), Ph. damselae subsp. damselae (Formerly V. damsela, 10 strains), V. campbellii (6 strains), V. costicola-like (6 strains), V. fisheri (5 stains), V. fluvialis (4 strains) and others Vibrio sp. (24 strains) by combining of biochemial and genetic characteristics.

• Journal of fish pathology
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• v.26 no.3
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• pp.129-137
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• 2013

The study surveyed infection rate of Kudoa septempunctata parasitized in the trunk muscle of olive flounder, Paralichthys olivaceus, cultured in Jeju Island and wild fish species caught in the coastal area around Jeju Island during 2012. Among 143 olive flounder that were randomly sampled from 26 different culture farms, K. septempunctata was detected in 7 fish samples (4.9%) from 4 different culture farms, showing no typical Kudoa infestation. However, K. septempunctata was not detected in olive flounder fry sampled from hatcheries and 8 species of wild fish. In addition, we compared 3 different sampling sites on trunk muscle of 7 Kudoa positive fish that included head part, tail part and entire muscle. Among 7 fish, K. septempunctata was detected in 3 fish that were sampled from head part; while 4 fish from tail part of trunk muscle. However, all 7 fish were positive when sampled from entire muscle. Thus, we suggest that it will be more efficient to use entire muscle sample than sampling partial muscle parts for detection of K. septempunctata.

• Journal of Life Science
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• v.34 no.9
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• pp.632-638
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• 2024

The antimicrobial activity of Bacillus amyloliquefaciens JFP-02 against nine fish pathogenic bacteria isolated from olive flounder aquaculture farms on Jeju Island was assessed under various medium compositions, pH levels, and incubation temperatures. The fish pathogenic bacteria isolated were Flexibacter maritimus, Staphylococcus caprae, Edwardsiella tarda, Streptococcus parauberis, Photo-bacterium damselae, Vibrio harveyi, Vibrio campbellii, Vibrio alginolyticus, and Vibrio anguillarum. The antibiotic susceptibility testing results for the fish pathogenic bacteria indicated the highest sensitivity to florfenicol, followed by gentamycin and neomycin. The bacteria exhibited the greatest resistance to penicillin, with amoxicillin and erythromycin showing the next highest levels of resistance. B. amyloliquefaciens JFP-02 exhibited the highest growth activity at pH 9, while the greatest antimicrobial activity was observed at pH 6. Likewise, although the highest growth occurred at 30℃, the most significant antimicrobial effect was observed at 20℃. Among the various medium components, the antimicrobial activity of B. amyloliquefaciens JFP-02 was highest when dextrin was used as the carbon source, leading to the greatest growth and antimicrobial activity. Additionally, among the nitrogen sources, the addition of yeast extract resulted in the highest growth and antimicrobial activity. For inorganic salts, although the highest growth activity was observed with MgSO₄·7H₂O and FeSO₄·7H₂O, the greatest antimicrobial effect was observed with KH₂PO₄.

• Journal of fish pathology
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• v.13 no.1
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• pp.45-51
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• 2000

Bacterial diseases with mixed infection have recently occurred at land-based flounder farms in Korea. Thus, single antibacterial is not effective for therapy of mixed bacterial diseases of fish because of their different causative bacteria. The purpose of the present study was to obtain basic data for positive usefulness of a combination of antibacterials used for synergism to mixed bacterial diseases of fish. Snergistic interaction in combination of antibacterials was determined by in vitro antimicrobial activity against selected fish-pathogenic bacteria, Vibrio anguillarum, Edwardsiella tarda, Streptococcus sp., Staphylococcus epidermidis, on the basis of Checkerboard assay using fractional inhibitory concentration (FIC) indices. Synergistic interactions were observed in combinations of (oxytetracycline HCL+lincomycin), (tetracycline HCL+florfenicol), (oxytetracycline HCL+florfenicol) against V. anguillarum, (sodium nifurstyrenate+florfenicol), (tetracycline HCL+florfenicol), (sodium nifurstyrenate+oxolinic acid), (oxytetracycline HCL+florfenicol) against E. tarda, (ciprofloxacine+oleandomycin), (oxytetracycline HCL+oleandomycin), (tetracycline HCL+oleandomycin), (oxytetracycline HCL+lincomycin), (oxytetracycline HCL+spiramycin), (oxytetracycline HCL+erythromycin), (doxycycline HCL+oleandomycin), (tetracycline HCL+spiramycin) against Streptococcus sp., and (ciprofloxacine+erythromycin), (florfenicol+erythromycin), (doxycycline HCL+oleandomycin), (ciprofloxacine+oleandomycin) against S. epidermidis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.285-289
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• 1997

A Held experiment was carried out to confirm the effect of underwater sound on the luring of fish school of rudder fish in a set net at the coast of Cheju Island. The effects of the acoustic emission on the luring of fish school were observed at a cage around a set net fishing ground using a manufactured underwater speaker. Underwater sounds that were emitted for the luring of fish school were the pure sounds of which frequency were 300Hz and 400Hz, engine noise and swimming sound. The results of the observation are as follows : 1. The input and output wave forms of a manufactured underwater speaker in water tank were similar to those in measurement frequencies. The result of the observation indicated that it could be used for the purpose of the sound emission in measurement frequencies. 2. The effect of the emitted pure sound of 300Hz, 400Hz was remarkable for the luring of fish school in 2 minutes after the sound emission. The reaction of fish school was more sensitive to the pure sound of 400Hz than 300Hz. 3. The effect of the emitted engine noise was more remarkable than that of the pure sound for 3 minute continuously. On the feeding sound, fish formed a shoal and swimmed, but didn't gather around the underwater speaker. 4. The feeding and swimming sound spectra on rudder Hsh showed similar sound pressure distribution each other, they appeared low sound pressure in frequencies of 200-600Hz.

• Journal of Aquaculture
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• v.10 no.1
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• pp.9-15
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• 1997

The pathogenic organisms occurred in cultured marine fishes in Kamak Bay were investigated from March to November in 1993. The samples were collected at 7 sampling stations once a month. Nine species of pathogenic organisms (Vibrio sp., Edwardsiella sp., Flexibacter sp., Streptococcus sp., Micrococcus sp., Caligus sp., Trichodina sp., Lymphocystis and Staphylococcus sp.) were identified as pathogenic organisms from four different species of fish (Sebastes schlegeli, Paralichthys olivaceus, lateolabrax japonicus and Pagrus major) collected in the study areas. Most of pathogenic organisms were found at over 20^{\circ}C$ of sea water temperature from June to October in 1993. On the test of drug sensitivity, Vibrio sp. (KS-9303) was sensitive to oxytetracycline and chloramphenicol ; Edwardsiella sp. (KP-9315) to oxytetracycline ; Flexibacter sp. (KP-9318) to oxytetracycline, chloramphenicol and oxolinic acid ; Streptococcus sp. (KP-9319) to erythromycin, chlorampheicol and oxytetracycline. However, all these 4 isolated bacteria were resistant to ampicilin, steptomycin, sulfamethoxazole and nitrofurazone.