• Journal of fish pathology
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• v.21 no.3
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• pp.247-257
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• 2008

To understand the activity of non-specific defence factors in cultured Sebastes, the antibacterial effect of the serum, skin mucus and homogenate of various organs from cultured oblong rockfish (Sebastes oblongus) and rockfish(Sebastes schlegeli) against pathogenic bacteria, Aeromonas hydrophila, Edwardsiella tarda, Vibrio anguillarum, and Streptococcus sp. was compared with that of flounder(Paralichthys olivaceus) and seabass(Leteolabrax japonicus). And the activities of proteolytic enzyme, chitinolytic enzyme and haemolycin as non-specific defence factor were investigated on the oblong rockfish and rockfish. Samples from oblong rockfish showed the highest antibacterial activity by lysoplate assay on agar plate mixed with pathogens, followed in descending order by rockfish, seabass, and flounder. Turbidimetric assay was carried to evaluate the lysozyme activity of fish samples against lyophilized cells of Micrococcus lysodeiktikus. The serum, kidney, liver, stomach, intestine and eyeball of oblong rockfish and the mucus and gill of rockfish appeared to have the highest lysozyme activity among the fish strains investigated. All samples except skin mucus, liver, and eyeball of oblong rockfish and rockfish showed proteolytic enzyme activity. Chitinolytic enzyme activity was showed in random sampling and haemolytic activity was remarkable in oblong rockfish. Therefore, Sebastes strain was proved to have effective defense mechanisms based on the antibacterial activities, and lysozyme, proteolytic enzyme, chitinolytic enzyme, and haemolycin were considered to act as the non-specific defence factor of Sebastes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.540-545
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• 2013

This study investigated the effect of diets supplemented with different levels (0, 1, 3, and 5 %) of turmeric Curcuma longa L. powder (TP) on the body composition of black rockfish Sebastes schlegeli. Fish weighing $10.05{\pm}0.44$ g were fed to apparent satiation twice daily for 8 weeks. Adding TP decreased crude lipid levels and increased crude protein and ash levels. Abundant fatty acids in the TP-added group were C16:0, C18:1 n-9 (cis), and C22:6 n-3. The major amino acids in samples were glutamic acid, aspartic acid, glycine, leucine, alanine, lysine, and arginine.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.3
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• pp.738-745
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• 2016

Aquaculture production of Korean rockfish Sebastes schlegeli has been continuously increased from 2000s and the fish has become the second most important mariculture fish in Korea. However, there are some environmental problems in aquaculture of Korean rockfish recently. In this regards, stress responses to high water temperature was examined via oxygen consumption, blood physiological parameter and endocrinological method. Oxygen consumption of Korean rockfish had significantly increased with rising water temperature. And oxygen consumption during the light time was no different with the dark time. The levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) showed no difference until $27^{\circ}C$, but it had rapidly increased at $30^{\circ}C$. Moreover high water temperature affected to increase in plasma glucose and cortisol levels.

• Environmental Analysis Health and Toxicology
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• v.17 no.3
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• pp.239-243
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• 2002

Changes of plasma vitellogenin (VTG) and glutamate pyruvate transaminase (GPT) were examined for determining whether hepatocyte was damaged during the process of VTG induction in the juvenile rockfish, Sebastes schlegeli exposed to exogenous estrogen (estradiol-l7$\beta$, E$_2$). Rockfishes were intraperitoneally injected with E$_2$(5 mg/kg B.W.) in 70% ethanol and plasma sampling were extracted at 0, 1, 3, 6, 9, 12, 15 days af-ter E$_2$administration. VTG and GPT were then analyzed by SDS -PAGE and Reitman -Frankel method, respectively. VTG band was detected at a molecular weight position of 175 kDa on Day 3 after E$_2$administration. This band became more distinct at 6 days, but its was gradually thinned with time -course, and not detected at 15 days. GPT was suddenly increased at 1 days after 22 administration and highest GPT was detected at 3 days. However. GPT was gradually decreased with time -course as the change of VTG. These results suggest that the process of VTG induction by exogenous E$_2$damage to hepatocyte, and plasma GPT was temporarily increased in the juvenile rockfish.

• Parasites, Hosts and Diseases
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• v.55 no.2
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• pp.219-224
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• 2017

In July 2012, philometrid nematodes were discovered in cultured rockfish (Sebastes schlegeli) in Cheonsuman (Bay), the Republic of Korea. The nematodes were detected in the epithelial tissues of the rockfish and were identified as Clavinema mariae based on morphological studies using light and scanning electron microscopy. They revealed the characteristics same as previously identified C. mariae, notably having a long body with narrow posterior half, no caudal projection, a cylindrical-shaped esophagus, a well-developed anterior bulbous part of the esophagus, cephalic papillae, and a dorsal esophageal gland. This is the first confirmation of C. mariae infection in rockfish in Korea.

• Fisheries and Aquatic Sciences
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• v.7 no.3
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• pp.99-108
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• 2004

Vitellogenin (VTG) was purified from serum of $estradiol-l7{\beta}-treated rockfish$(Sebastes schlegeli) by precipitation with $EDTA-Mg^{2+}$ and ammonium sulfate and two step chromatography (anion exchange chromatography and gel permeation chromatography) was performed on FPLC system. Rockfish VTG (rfVTG) was characterized and its properties were determined. The monomers have apparent, molecular mass of about 188 kDa as indicated by SDS-PAGE. Amino acid composition analysis of rfVTG was similar to VTG from other oviparous teleosts. Cysteine and lysine were present at relatively high level. Leucine was present at relatively lower level than in other species. The N-terminal amino acid sequence was evaluated to identify rfVTG. Western blot analysis using an antibody against the purified VTG showed that the antibody reacted with both plasma of $estradiol-l7{\beta}-treated rockfish$ treated male and purified VTG, whereas there was no reaction with male serum of the control. An ELISA was developed using monoclonal and polyclonal antibodies against rfVTG. The assay range was 3.2 ng/mL and 1,000 ng/mL and the value of the intra and inter assay variations were within $9.7{\%}$ and $11.2{\%}$, respectively. Recovery rate was $96.8{\%}$. The sandwich ELISA could be useful for the detection of VTG and could be good for screening of estrogenic compounds.

• Fisheries and Aquatic Sciences
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• v.6 no.4
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• pp.213-219
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• 2003

Experiments were carried out to investigate the accumulation and elimination changes in the tissue of juvenile rockfish (Sebastes schlegeli) after sub-chronic dietary Cu (0, 50, 125, 250 and 500 mg/kg) exposure for 60 days and depuration for 30 days. The profile of Cu accumulation in the tissue of rockfish was dependent on the exposure periods and Cu concentration. Liver of rockfish is a more important storage tissue than other tissues, and the order of Cu accumulation in tissues was liver > intestine > kidney > gill > muscle. The accumulation factors were increased with the exposure period in gill, intestine, liver, kidney and muscle. An inverse relationship was observed between the accumulation factor and the exposure concentrations in the gill, kidney and muscle. Cu elimination in tissues of rockfish were decreased with periods for the 30 days of depuration except kidney and muscle. The order of Cu elimination in organs during depuration was intestine > liver > gill.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.3
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• pp.432-442
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• 2020

Diagnostic monitoring in Korean rockfish cages was performed to survey the prevalence of pathogens in cultured Korean rockfish Sebastes schlegeli from May 2013 to July 2016. A total of 1,945 fish samples collected from the western (Cheonsu Bay and Heuksando), southern (Tongyeong and Namhae), and eastern coasts (Pohang) of Korea were tested for parasites, viruses, and bacteria. In this study, 1,264 and 334 fishes were infected with Microcotyle sebastis and Clavinema mariae, respectively. The prevalence rates of C. clavinema in fishes from Cheonsu Bay, Heuksando, and Tongyeong were 35.3%, 3.9% and 1.9%, respectively. No C. clavinema infection was detected in cultured rockfish from Namhae and Pohang. Furthermore, bacteria including Photobacterium damselae (8.9%), Photobacterium piscicola (2.3%), Photobacterium spp. (8.9%), Aeromonas salmonicida (1.8%), Aeromonas spp. (0.9%), Vibrio scophthalmi (1.5%), Vibrio spp. (3.3%), Streptococcus iniae (1.2%), and others (8.0%) were detected in 373 of 1,364 fishes. No virus was detected in any fish investigated in this study.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.4
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• pp.372-377
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• 2017

A feeding trial was conducted to evaluate the effects of partial replacement of fishmeal (FM) protein in a practical diet for rockfish Sebastes schlegeli juveniles with mealworm Tenebrio molitor meal (WM), in terms of growth performance, feed utilization, whole body composition and hematological parameters. Four isonitrogenous and isoenergetic diets were formulated to contain 8, 16, 24 and 32% WM (designated as WM8, WM16, WM24 and WM32). A FM-based diet without WM inclusion was used as a control. Triplicate groups of rockfish ($2.6{\pm}0.07g$) were hand fed one of the experimental diets to visual satiation twice a day for 8 weeks. Weight gain of fish fed the WM32 diet was lower than that of control. No significant differences were found in daily feed intake, feed efficiency and protein efficiency ratio. The whole-body protein content of fish fed WM0 and WM8 diets were significantly higher than that of fish fed WM32 diet. No statistical differences were observed in hematological parameters. These results indicate that WM has potential as alternative to FM in practical diets for juvenile rockfish and can be used at an inclusion level of up to 24% without having a significant negative effects on growth and feed efficiency.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.5
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• pp.603-610
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• 2014

We investigated a nematode infection in the epithelial tissue of rockfish Sebastes schlegeli cultured in Cheonsu Bay, western Korea, from May 2013 to April 2014. Nematodes infected the epithelial tissues of various external organs, including the fins, operculum, nares, mouth, and head. Over a 1-year period, the overall nematode infection rate in rockfish was 55% (n=89/163): 56.7% (n=17/30) in May 2013, 88% (n=29/33) in August 2013, 0% (n=0/30) in October 2013, 70% (n=21/30) in January 2014, and 55% (n=22/40) in April 2014. During this study, the only mass mortality of cultured rockfish in Cheonsu Bay was in August 2013, when we identified skin wounds on the rockfish caused by the nematodes escaping from their hosts. During this period, the accumulated mortality for 2 weeks was 1.4-22.4% in different farms. In addition, several pathogenic bacteria (Photobacterium damselae, Vibrio spp., and Streptococcus iniae) were isolated from the moribund rockfish; these were thought to be transmitted through the skin wounds caused by the nematodes.