• Journal of fish pathology
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• v.24 no.2
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• pp.121-129
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• 2011

Aquatic animal raised in hatcheries play an important role in supplying seedling to stock enhancement and seed quality, especially, seed health is the key factor for survival in the field after release and for stocking effectiveness. We have inspected the hatchery-reared seeds of 33 marine species and 12 freshwater species for legally designated diseases in stock enhancement program in 2010. Results showed that abalone was the most abundant as 20.0% in the marine species group and then sea cucumber (15.6%), olive flounder (8.4%), rockfish (6.7%), black sea bream (6.3%) and swimming crab (6.1%) were followed. Crucian carp was the most abundant as 19.4%, and then eel (11.8%), Korean bullhead (10.9%), mandarin fish (10.8%), melanian snail (8.4%), catfish (7.7%) were followed in the freshwater species group. The total number of inspection cases for eight pathogens in this study were 2,105 and disqualification cases were 30 by detection of aquatic animals pathogens such as koi herpesvirus (KHV), red sea bream iridovirus (RSIV), white spot syndrome virus (WSSV) or viral haemorrhagic septicemia virus (VHSV).

• 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.

• Korean Journal of Ichthyology
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• v.10 no.2
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• pp.207-215
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• 1998

Just after hatching the embryo has a yolk sac and straighted digestive tract. Just after parturition in 5.0mm TL the mouth and anus were opened. In the larval stage of 5.2mm TL, digestive tract could be divided into pharynx, esophagus, stomach, pyloric caeca and intestine of the early differentiated state. The esophagus of larvae in 5.3mm TL has a PAS positive mucous cell. From over 5.7mm TL, PAS positive goblet cell recognized in the intestine. PAS positive absorptive cell began to appear in the intestine from 5.9mm TL. Yolky materials were absorbed completely in 6.0mm TL. In the larvae of B.5mm TL, gastric glands were observed in the mucosa, but the surface epithelium did not have PAS positive granules. From over 9.0mm TL, the histological structure of esophagus showed similar to adult. In the juvenile stage from 13.0mm to 15.0mm TL, histological structure of the stomach, pyloric caeca and intestine showed similar to adult. From the ultrastructural and histochemical study, it is concluded that the functional digestive tract is present in the juvenile stage from 18.0mm to 20.0mm TL.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.594-599
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• 2012

The objective of this study was to determine the processing conditions for salt dried rockfish Sebastes schlegeli by sun drying and cold-air drying, as measured by alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activity. We processed salt dried rockfish samples. The salinity of rockfish samples was within 1% following salting with 25% salt brine for 3 h. The moisture content of salt dried rockfish was found to reduce linearly from 70.12 to 39.5 g/100 g over the same time interval. The water activities of salt dried rockfish by sun and cold-air drying were 0.94 and 0.87, respectively, after three days of drying. Acid values (AV) were 10.71 and 5.96 mg KOH/g, respectively, after the three day drying period. The ADH activity in a water extract from salt dried rockfish following sun and cold-air drying for 24 h was 228.5% and 226.1% at 13.3 mg/mL, respectively, and was higher than that when drying lasted for 48 and 72 h. The ALDH activity was not affected but both ADH and ALDH activity tended to decrease as the drying time increased from 24 to 72 h. The conditions of processing for the best quality of salt dried rockfish were determined to be drying with a cold-air system for 24 h. These results indicated that water extracts from salt dried rockfish have valuable biological attributes owing to the metabolizing of alcohol and can provide useful information for the design of drying systems for salt dried rockfish.

• Journal of Veterinary Clinics
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• v.23 no.2
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• pp.164-168
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• 2006

The residue depletion of ampicillin was investigated in the olive flounder (Paralichthys olivaceus), rockfish (Sebastes schlegeli), and red sea bream (Pagrus major) after 5 days treatment with medicated feed at a dose of 100 mg/kg bw/day. Fishes were sampled for muscle on 1st, 2nd, 3rd, and 4th day after treatment. Ampicillin concentrations were determined by high performance liquid chromatography after SPE column extraction. The recovery rates of ampicillin in muscle samples ranged 94-98% and 83-88% for the concentration of 0.05 mg/kg and 0.1 mg/kg, respectively. Ampicillin concentrations detected on 1st day after treatment were 0.143, 0.138, and 0.187 mg/kg in the muscle of olive flounder, rockfish, and red sea bream, respectively. After a withdrawal of 3 days, muscle concentrations were 0.016, 0.012, and 0.021 mg/kg in the olive flounder, rockfish, and red sea bream, respectively. Ampicillin was not detectable in muscle samples on 4 days following withdrawal of the medicated feed. From results of the present study, a withdrawal period of ampicillin is proposed on 5 days after 5 days treatment with medicated feed at a dose of 100 mg/kg bw/day to avoid the presence of excessive residues of the edible muscles of olive flounder, rockfish, and red sea bream.

• Journal of Food Hygiene and Safety
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• v.17 no.4
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• pp.193-200
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• 2002

Three species of fish such as yellow tail (Seriola quinqueradiata), bastard halibut (Paralichthys olivaceus) and black rockfish (Sebastes schlegeli) were exposed to the dinoflagellate, Cochlodinium polykrikoides, and quality changes of fish after death were investigated during the extended storage. The volatile basic nitrogen (VBN) and aerobic plate counts (APC) were determined in the muscles of fish, arid organoleptic change was evaluated in the kills, skins and muscles. APC in all the fish species did not change in 6 hours of storage, but increased gradually thereafter. VBN contents in the muscles continuously increased throughout the storage of fish. Slightly higher levels of APC and VBN were observed in the tested fish than control fish, which had been exposed to air until died and stored in seawater without treating C. polykrikoides. After 12 hours of storage, APC and VBN contents in the muscles did not exceed the initial spoilage limit, 10$^{5}$ CFU/g fur APC and 30 mg/100 g for VBN, in all of the fish including control fish. Organoleptic change in fish treated with C. polykrikoides did not greatly differ from the control fish. After 8 hours of storage, distinctive deterioration of muscle was detected organoleptically in the treated fish and the control fish. The compiled result indicated that moribund fish exposed to C. polykrikoides bloom should be handled properly in 6 hours of storage after death of fish.

• Journal of fish pathology
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• v.11 no.1
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• pp.13-22
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• 1998

To know the features of Amyloodinium sp. parasitized in Black seabream, Acanthopagrus schlegeli, morphology and reproduction type of the parasite were investigated. Infection mode and histopathology of the parasites were also studied. In the developmental and morphological observation, the parasite passed through parasitic and non-parasitic phases with three developmental stages termed trophont, tomont, and dinospore. The trophont, 30-$80{\mu}m$ ovoidal or pyriform, for the vegetative stage had a spherical nucleus with $1.5{\mu}m$ in diameter, many food vacuoles and starch grains in cytoplasm. The tomont, 80-$90{\mu}m$ spherical, for the reproductive stage resorbed a stalk, secreted a cyst wall and reproduced within it. A dinospore, small 10-$15{\mu}m$ biflagellated, for the infestation stage had a stigma. The parasite was propagated for 15 days by serial passage in Korean rockfish (Sebastes schlegeli) at $25{\pm}1^{\circ}C$. Trophonts began to detach from the fish about 3 days after infection and was completed within 5 days at $25{\pm}1^{\circ}C$. It took from 3 to 5 days to reproduce at the same temperature. Reinfected fish showed that parasites penetrated under the epithelia of gill filament and gill lamellae causing hyperplasia and degeneration at infected area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.633-642
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• 1994

Distribution of ichthyoplankton in the adjacent waters to Kori were surveyed during the period from April, 1991 to January, 1992. The dominant fish eggs included the eggs of Engraulis japonica, Maurolicus muelleri, Callionymus spp. and others. The eggs of Engrualis japonica and Maurolicus muelleri were $79.52\%$ and $1.86\%$ of the total eggs abundance, respectively. A total of 15 taxa of fish larvae were found. The dominant species was Engraulis japonica accounting for $52.39\%$ of the total larvae and followed by Callionymidae fish($29.36\%$). Other major species were Stephanolepis cirrhifer($6.30\%$), Sebastes schlegeli($3.16\%$), Ammodytes personatus($1.33\%$) and Girella punctata($1.70\%$). These 6 taxa constituted $94.30\%$ of the total larvae collected. In this area, distributions of warm water had a great influence on larvae and juvenile distribution which usually is along the coast and the other places where there layer water movements since, upwelling in the open sea affects ichthyoplankton distribution.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.495-500
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• 2015

Currently the fish aquaculture industry of Korea is focused on the mass culture of flatfish (Paralichthys olivaceus) and and rockfish (Sebastes schlegeli) with completely controlled culture techniques. Recently, there has been considerable interest in new species development, such as the starry flounder (Platichthys stellatus). The value of starry flounder (Platichthys stellatus) as a raw fish increases with time because it is tasty, light, and bouncy. In this paper, the growth characteristics dependent on the LED wavelengths and the optimal growth conditions of the starry flounder were studied. In these experiments 4 different kinds of LED lighting, configurations were designed and prepared using red, green, blue and white, respectively. The fish aquaculture experiments were conducted over 10 weeks in four fish tanks, each installed with a different color of LED lighting. 10 starry flounders of 13 ~ 17g were placed into each tank. The effects of each color of light on the growth rate of the starry flounders were then examined. As a result, the starry flounders under the green LED lighting showed the highest growth rate, followed by the white, red, and blue LED lighting. Based on these results, a green light provides a suitable breeding environment for the starry flounder.

• Journal of fish pathology
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• v.36 no.2
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• pp.277-286
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• 2023

Korean rockfish, Sebastes schlegelii, is a representative bony fish that belongs to the family Scorpaenidae and the order Scorpaeniformes. It has high ecological and economic value and is widely cultivated in many East Asian countries, including South Korea, Japan and China. One of streptococci, Streptococcus iniae, is Gram-positive cocci with a negative reaction for catalase and oxidase. The Korean rockfish shows clinical signs when infected with S. iniae, such as body darkening, bleeding, enlarged kidneys, blurred eyes, abdominal distension, etc., ultimately leading to death. The Korean rockfish causes significant economic losses every year in South Korea due to streptococcosis. In this study, we identified bacteria from the fish using polymerase chain reaction and conducted analyses of hemolytic activity and biochemical tests using API 20 STREP and API ZYM systems. Results of confirming the hemolytic activity (n=4) observed in alpha-type hemolysis (25%), beta-type hemol- ysis (50%), and gamma-type hemolysis (25%) of isolates. The biochemical test results exhibited sig- nificant variation among S. iniae. Additionally, we performed intraperitoneal injection with S. iniae in the fish and analyzed the phylogenetic tree using housekeeping genes of S. iniae, including cpsD, arcC, glnA, groEL, gyrB, mutS, pheT, prkC, rpoB, and tkt, via multilocus sequence typing (MLST). The lethal dose (LD₅₀) showed strong pathogenicity, such as 3.34 × 10 colony-forming unit (CFU)/ml for 23FBStr0601 strain and 7.16 × 10 CFU/ml for 23FBStr0602 strain. 23FBStr0603 strain showed relatively low pathogenicity at 1.73 × 10⁵ CFU/ml. The strains 23FBStr0601 and 23FBStr0602, which showed strong pathogenicity, clustered into one monophyletic group. The 23FBStr0603 strain showed weak pathogenicity and formed a monophyletic group with KCTC 3657.