• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.1
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• pp.50-55
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• 2012

We compared the nutritional requirements of whole larvae of the black seabream Acanthopagrus schlegeli, sweet fish Plecoglossus altivelis, olive flounder Paralichthys olivaeus and rock fish Sebastes schlegeli. The larvae were 20, 30, 14 and 5 DAH (or spawning) of black seabream, sweet fish, olive flounder and rock fish, respectively. Specific ${\alpha}$-amylase activity (mU/mg protein) was highest (8,324.9 mU/mg protein) in rock fish larvae (P<0.05). Specific trypsin-like protease activity was highest (11,330.1 mU/mg protein) in black seabream larvae (P<0.05), which also exhibited the highest activity, 685.5 mU/mg dry weight (P<0.05). The specific activities per mg protein and mg dry weight of black seabream were the highest (187.4 mU/mg protein and 11.3 mU/mg dry weight, respectively) (P<0.05). A/P, P/L and A/L ratios of rock fish were 1.47, 90.3 and 133.1, respectively (P<0.05). We present here basic larval digestive enzymatic nutritional requirement data.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.4
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• pp.1184-1193
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• 2015

Monitoring for megalocytivirus infection was conducted for ten months from March to December in 2013 in 15 aquatic farms culturing, red sea bream, rock bream, rock fish and black sea bream around Tongyoung coastal area in Korea, to assess spatial and temporal variability of detection prevalence, and to explore possible links with seawater temperature. In nested-PCR targeted major capsid protein (MCP) gene, asymptomatic megalocytivirus infection was detected in the externally healthy farmed fish with a significant prevalence in range from 0 to 58.3% for ten months. Higher prevalence of megalocytivirus (46.7% - 57.1%) was observed in high water temperature season from September to November than that in other months with lower prevalence of 0.0% to 20.0%. Even though an acute infection of megalocytivirus was occurred in rock bream (positive in the first PCR) with high mortality in one of fifteen farms, there was no expansion or transmission of the disease to the rock fish and red sea bream culturing in net cage just proximal to the rock bream cage in which disease outbreaked. Nucleotide sequence analysis of the cloned MCP gene isolated asymptomatically infected rock fish revealed that the megalocytivirus in this study was clustered together with the rock bream iridovirus (RBIV) under the subgroup II of the genus megalocytivirus (Iridoviridae), which is known to be the major megalocytivirus strain in Korea. The typical histopathological signs were not found in the spleen of rock fish asymptomatically infected by megalocytivirus. Experimental infection of rock bream with the spleen homogenate of the rock fish infected asymptomatically did not induce any mortality unlike the homogenate of infected rock bream with hih mortlity. However, these results may suggest that the asymptomatic infection of megalocytivirus in other fish species can be a potential risk threatening aquaculture industries as a transmission factor of megalocytivirus to susceptible fish species, especially rock bream.

• Journal of Fisheries and Marine Sciences Education
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• v.12 no.1
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• pp.1-10
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• 2000

In order to obtain the fundamental data on the auditory thresholds of fishes for marine ranching, the auditory thresholds of black rock fish Sebastes Schlegeli were measured in the presence of masking noise in the spectrum level range of 73 - 83dB (0dB re $1{\mu}Pa/{\sqrt{Hz}}$) with a classical cardiac conditioning technique. Critical ratios were about 19 - 30dB at 80 - 300Hz and 46 - 54dB at 500 - 800Hz. The ratio increased almost linearly with increasing frequency to 500Hz. The noise spectrum level at the start of masking was about 70dB within the frequency range of 80 - 800Hz excepting 65dB at 300Hz. This suggests that hearing of the black rock fish is masked in the natural environment with the noise spectrum level above 65dB. The sound pressure level of which the signal sound of 100 - 200Hz is recognized by black rock fish under the ambient noise is above 90dB and the critical ratio of them is above 20dB.

• Journal of fish pathology
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• v.24 no.3
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• pp.225-236
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• 2011

This study was aimed to determine the fish physical status according to the gross and histopathological findings of liver in cultured black rock fish, Sebastes schlegeli. All 47 fish submitted had no marked abnormalities in the external findings. 42.55% of fish showed normal liver, 25.53% yellow liver, 25.53% atrophic brown liver, 4.26% yellowish-green liver and 2.13% fatty liver in gross examination. Grossly normal liver showed no remarkable change in lobular structure but many vacuoles were found in hepatic cell. Hepatic cells took normal roundish, polygonal shapes containing spherical nuclei. In group of yellow-brown liver, many brown pigments were seen in hepatic cells, MMCs and brown-colored hyaline droplets within cytoplasm of hepatocytes. Yellowish green pigments were seen in hepatic cells and MMCs of yellow green liver and green colored hyaline droplets within hepatocytes. The dilated central veins are highlighted with atrophy of hepatic cells. Outline of atrophic hepatocyte became ambiguous and nucleus frequently become small and pyknotic. Fatty liver showed prominent vacuolar structures in cells as clear spaces or foamy cytoplasm with degenerative nuclei. From these results, it was strongly suggested that hepatic gross and histological findings could be used as important and critical health parameters of fish prior to progression to substantial manifestation as clinical disease.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.1
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• pp.20-25
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• 2008

The susceptibility of five different marine fish to iridovirus IVS-1 infection was analyzed and found a higher the cumulative mortality in the order of rock bream (Oplegnathus fasciatus), red sea bream (Pagrus major), sea perch (Lateolabrax sp.), rockfish (Sebastes schlegeli) and black porgy (Acanthopagrus schlegeli). However, the concentrations of virus in the infected spleens of these species did not differ significantly. To determine the release of iridovirus from infected fish into culturing seawater, rock bream were challenged with iridovirus IVS-1 and the concentration of virus in the water was analyzed using PCR. Over the 10 days of the analysis, the linear relationship between the number of dead fish and viral DNA concentration found in culturing seawater should be considered direct evidence of horizontal iridovirus transmission.

• Journal of Fisheries and Marine Sciences Education
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• v.11 no.1
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• pp.88-97
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• 1999

Auditory thresholds were determined by means of a conditioned response to sound stimuli at frequencies 80, 100, 200, 300, 500 and 800 Hz for a 10 black rock fish, Sebastes schlegeli. The conditioned response was a change of a cardiac rhythm. It was established through an electric shock as unconditioned stimulus, and could be monitored on an oscilloscope. A stable acoustic condition was obtained by suspending the fish in a small cage at fixed position in the test tank. The sensitive frequencies ranged from 80 Hz to about 800 Hz, showing the best frequency around 100 Hz where the mean threshold value was 90.5 dB. A gradual rise below 300 Hz and a relatively sharp turn above 500 Hz were indicated in the audiogram. The method presented here seemed to be useful for a rapid determination of the audiogram of fishes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.2
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• pp.78-84
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• 2006

A high performance liquid chromatography assay method for spiramycin in fish muscle was developed. The developed method was evaluated and validated by monitoring spiramycin in olive flounder (Paralichthys olivaceus), black rock fish (Sebastes schlegeli) and in live conger eel (Anguilla japonica) in fish farms and distribution centers. Using the developed method, the recovery rate was up to 82.4-88.8%, which was higher than that of conventional methods (77.6-87.1%). In particular, the proposed sample treatment protocol was suitable for use with fish samples to remove low molecular weight materials and pigments that could interfere an accurate analysis. The prepared stock solution was very stable, and it remained chemically stable for 5 weeks at $4^{\circ}C$. The performance limit of the developed method for spiramycin acid in fish muscle was 0.05 ppm. One hundred thirty-four fish samples including olive flounder, black rock fish and live conger eel were analyzed to evaluate the overall efficiency of the modified method and to monitor the actual condition of spiramycin usage in fish farms. Olive flounder and black rock fish were collected from fish farms in coastal areas of Korea, and live conger eels were purchased from a fish market in the Busan area from September 2001 to March 2002. According to the overall performance of the developed method, it was considered suitable for the monitoring of spiramycin in fish muscle. The suggested method of analysis for spiramycin in fish muscle is registered in the Korean Official Methods of Food Analysis and is currently tieing utilized for fishery products inspection by the Korea Food and Drug Administration and the National Fisheries Products Quality Inspection Service.

• Journal of fish pathology
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• v.19 no.3
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• pp.277-284
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• 2006

Application of wood vinegar in fish farms has been used for the disinfection of pathogenic microorganisms and the treatment of infectious diseases. This study was performed to know the acute toxicity of wood vinegar to carp Cyprinus carpio, flounder Paralichyhus olivaceus, rock fish Sebastes schlegeli and black sea bream Pagrus major. The 24 hr, 48 hr and 96 hr LC50 respectively were: carp 1243, 1143 and 1016 ppm; flounder 1397, 1253 and 1226 ppm; rock fish 1058, 993 and 967 ppm; and black sea bream 650, 616 and 596 ppm. Death and survival of fish exposed to lethal concentrations of wood vinegar were apparently related to massive necrosis, fusion and epithelial lifting of gill lamellar epithelium, suggesting the osmotic imbalance and lack of oxygen uptake.

• Journal of fish pathology
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• v.19 no.3
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• pp.253-265
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• 2006

The purpose of this study was to obtain reference data of parameters for hematological health diagnosis in marine fish and also evaluate application of veterinary chemistry analyzer used to those blood tests. A blood profile of total 522 fish for black rockfish (Sebastes schlegeli), red seabream (Pagrus major), rock bream (Oplegnathus fasciatu) and black seabream (Acanthopagrus schlegeli) cultured in mari-floating netcage of Gyeongnam province was determined by hematocrit (Ht), hemoglobin (Hb) and blood chemistry tests (total protein, albumin, alkaline phosphatase, blood urea nitrogen, lactate dehydrogenase, triglyceride, total cholesterol, creatinine, aspartate aminotransferase, alanine aminotransferase, glucose). Ht was measured by microhematocrit method. Hb and plasma chemistry were analysed by establishing baseline ranges for a dry chemical system of FUJI DRI-CHEM 3000. Actually recorded values of Hb and plasma chemistry by the analyzer were notably outside from the minimum and/or maximum of the established reference value. Albumin and alanine aminotransferase were not detectable in the range of 68～66%. Lactate dehydrogenase, total protein, alkaline phosphatase and glucose were not detectable in the range of 42～21%. Total cholesterol, aspartate aminotransferase, triglyceride, hemoglobin and creatinine were not detectable in the range of 18～3%. However, the values of blood urea nitrogen were below the detectable limits of the analyzer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.2
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• pp.66-71
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• 2006

Fluoroquinoles have a wide range of antimicrobial properties and are effective in the treatment of bacterial diseases in fish. The use of fluoroquinoles continues to grow steadily. Fluoroquinolone antibiotics are probably the most important class used among synthetic antibiotics in human and veterinary medicines because of their broad activity spectrum and good oral absorption. This study was conducted to estimate the residue of antibiotics in four species of farmed fishes, including olive flounder (Paralichthys olivaceus), black rock fish (Sebastes schlegeli), red sea bream (Pagrus major), and sea bass (Lateolabrax japonicus), collected from fish farms located in the southern coastal area of Korea. The residues of fluoroquinolones were determined using high performance liquid chromatography (HPLC) with a fluorescence detector. Residuals of five fluoroquinolones in muscle tissue of farmed fish were analyzed. We found that enrofloxacin was the most common agent in fish muscle, and that ciprofloxacin was the next most common. The range of detected concentrations of fluoroquinolones in olive flounder muscle was 0-0.859 mg/kg in 32.6% of all samples. Enrofloxacin was commonly detected in sea bass muscle at a range of 0-0.143 mg/kg in 38.9% of all samples. Fluoroquinolones were detected in 6.9% of black rock fish muscle and in 16.6% of sea bream, although the detected concentration was below 0.01 mg/kg. The maximum detection value of enrofloxacin and ofloxacin in olive flounder at the time of shipping was 0.102 mg/kg and 0.09 mg/kg, respectively; no other antimicrobials were detected. We detected no antimicrobial substances in red sea bream.