• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.753-760
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• 2013

Two feeding trials were conducted to investigate the effects of feeding rate and frequency on growth performance and body composition of juvenile Korean rockfish Sebastes schlegeli reared at $15.0{\pm}0.3^{\circ}C$. In the first trial, three replicate fish groups averaging $2.07{\pm}0.03g$ were fed a commercial diet with one of seven different daily feeding rates: 1.00%, 2.00%, 2.50%, 2.75%, 3.00%, 3.25%, and satiation (3.34%) based on body weight (BW). After four weeks of feeding, fish fed the 3% diet showed significantly higher weight gain (WG) and feed efficiency (FE) than fish that received the other feeding rates. In the second trial, the optimum feeding frequency was evaluated with three replicate fish groups averaging $2.04{\pm}0.03g$. Fish were fed a commercial diet at 2.87% BW with six different daily feeding frequencies: 2, 3, 4, 5, 7, or 9 meals. After four weeks of feeding, WG, specific growth rate, FE, and protein efficiency rate in fish fed 3 meals $d^{-1}$ were significantly higher than those of fish fed 7 or 9 meals $d^{-1}$. In both feeding trials, proximate composition of the entire body changed depending on the feeding rate or frequency. A broken-line regression analysis based on weight gain suggested that the optimum daily feeding rate and frequency for juvenile Korean rockfish at $15^{\circ}C$ was 2.9% BW $d^{-1}$ and 2-3 meals $d^{-1}$, respectively.

• Journal of fish pathology
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• v.25 no.3
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• pp.231-241
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• 2012

Diagnostic monitoring in fish farms with land-based tanks and netpen cases were conducted in eastern, western, southern and Jeju island of Korea during summer of 2007~2011. In total, 2413-fish samples of 4 marine fish species were tested for the detection of bacteria and parasite. Fish species tested were olive flounder (Paralichthys olivaceus), black rockfish (Sebastes schlegeli), red sea bream (Pagrus major), pacific white shrimp (Litopenaeus vannamei). During the diagnostic monitoring from 2007 to 2011, the infection rates by single infection of bacterial or parasitic pathogens were relatively higher than the mixed infections. The main bacterial pathogens in olive flounder, black rockfish and pacific white shrimp were Vibrio spp. (V. harveyi, V. ichthyoenteri, Vibrio sp.). The main bacterial pathogens in red sea bream were also Vibrio sp. and Photobacterium damselae subsp. damselae. The main parasitic pathogens were both Miamiensis avidus and Trichodina sp. in olive flounder, Microcotyle sebastes in black rockfish, Microcotyle tai in red sea bream and Zoothamnium sp. in pacific white shrimp.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.203-209
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• 2015

Low-value fish is the most commonly used feed in Asian fish farms despite the fact that its application is controversial in regard to the sustainability and biosecurity of aquaculture. In this study, the causal agent of a disease outbreak at a Korean rockfish Sebastes schlegeli farm was investigated to determine whether the low-value fish used at the farm was the source. Infected Korean rockfish and Pacific sand eel used as feed were sampled from the farm, and bacterial cultures recovered from the internal organs of all sampled rockfish were isolated as pure cultures and later identified as Vibrio harveyi. The causal agent of the disease was also isolated from the kidneys of some of the sampled Pacific sand eels. This study provides additional evidence that the low-value fish used as feed at fish farms can be a key source of infectious diseases.

• Korean Journal of Ichthyology
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• v.25 no.1
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• pp.1-8
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• 2013

Rockfish, Sebastes schlegeli (total length; $10.36{\pm}0.49cm$, total weight; $16.28{\pm}1.86g$, N; 290) were exposed to various concentrations of naphthalene for 28 days. Exposure concentrations of naphthalene established control, ethanol (solvent) control, 0.5, 1.0, 1.5 and 2.0 mg Nap $L^{-1}$. After exposure, We observed survival rate, and degree of tissue change (DTC) in gill under optical microscopy. Survival rate of the rockfish was more than 90% in control, ethanol control, 0.5 and 1.0 mg Nap $L^{-1}$, whereas it decreased in 1.5 and 2.0 mg Nap $L^{-1}$ (respectively 80%, 62.2%). In histological observation of gill, hyperplasia of epithelial cells observed in all exposure groups. But no showed increase of DTC which was related to concentration. Whereas, DTC at fusion of gill lamellar, lamellar telangiectasia, stasis, aneurysm and necrosis showed dose dependent increase. Especially, fusion of gill lamellar, lamellar telangiectasia and stasis observed at more 1.0 mg Nap $L^{-1}$, and aneurysm and necrosis at more 1.5 mg Nap $L^{-1}$. These results showed naphthalene caused survival and severe change to the gill of the rockfish which was related to exposure concentration.

• Journal of Life Science
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• v.10 no.3
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• pp.292-299
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• 2000

This study was conducted to investigate the effects of different dietary dimethy-β -propiothetin (DMPT) levels on growth and body composition in Korean rockfish (Sebastes schlegeli) after a eight weeks feeding experiment. Body weight gain, feed efficiency and feed intake were significantly increased with dietary DMPT level. After eight weeks of feeding trial, moisture content decreased with supplemented DMPT level, while crude protein and lipid contents increased with dietary DMPT level. Amino acid content was elevated DMPT feeding groups compared to the control group. Amino acid composition was not significantly different in the dietary groups. Fatty acid content increased with dietary DMPT level.

• Journal of Aquaculture
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• v.7 no.2
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• pp.97-107
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• 1994

Experimental diets containing 5 different levels of a-cellulose $(0\%,\;5\%,\;10\%,\;15\%\;or\;20\%)$ were fed to juvenile Korean rockfish (20.5g of initial mean weight) for 10 weeks to study their ability to utilize dietary $\alpha-cellulose$. Weight gain, feed efficiency, and protein and energy retention efficiency in the fish fed diets containing $0\%,\;5\%,\;or\;10\%$ of $\alpha-cellulose$ were significantly higher than those in the fish fed diets containing $15\%\;or\;20\%$ of $\alpha-cellulose$ (P<0.05). Whole body lipid content of the fish fed $10\%$ $\alpha-cellulose$ diet were significantly higher than that of fish fed other diets (P<0.05). The results suggest that the optimum dietary fiber levels for Korean rockfish would be less than $10\%$.

• Journal of fish pathology
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• v.11 no.1
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• pp.29-33
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• 1998

Distribution of a monogenean helminth Microcotyle sebastis on the gills of cultured Korean rockfish (Sebastes schlegeli) was investigated with regard to gill arches, sides of gill hemibranches (anterior or posterior), and their sections (dorsal, medial and ventral). M. sebastis has a significant preference for the second and third pair of gills, and shows marked affinity for anterior hemibranches of each gill branch, and medial sections of each gill hemibranch. The results suggest that the larger volume of water flows and surface area of the second and third pair of gills might affect the distribution of M. sebastis, and the concentrated distribution of M. sebastis on the anterior medial section of gills would be related with the increasing chances of mating by niche restriction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.5
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• pp.458-462
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• 2003

This study was to survey proper condition of nitrate removal by hydraulic retention time (HRT) and measured growth of black rockfish (Sebastes schlegeli) and giant croaker (Nibea japonica) in the seawater recirculating culture system designed for nitrate removal. Nitrate conversion to nitrogen at 8 hr-HRT was higher than 16 hr-HRT, amounting to $32.2\;g/m^3/day$ in the seawater recirculating culture system. The removal efficiency of nitrate improved when dissolved oxygen was situated less than 0.5 mg/L. Daily growth rate (DGR) and feed efficiency (FE) of S. schlegeli with mean body weight of 108 g in 8 hr-HRT were significantly higher values than those in 4 hr-HRT (P<0.05). The DGR and FE of N. japonica with mean body weight of 12 g in added carbon system showed not differing in the values from N. japonica in control system (P>0.05).

• Journal of Aquaculture
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• v.8 no.3
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• pp.221-229
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• 1995

Two long term feeding trials using moist pellet diet were conducted to study the growth pattern of Korean rockfish (Sebastes schiegeli). Two groups of the fish with initially averaging of 6.8g and 11.0g were stocked in the indoor FRP tanks, and were fed with moist pellet for 22 months and 10 months, respectively. It took approximately 11 months and 23 months after parturition to grow up to 200g and 500g of average body weight, respectively. Average body weight of fish increased almost linearly, and no significant growth stagnation was observed even in winter (the lowest water temperature was $11^{\circ}C$) and summer (the highest water temperature was $25^{\circ}$) seasons. Growth rate, feed intake and protein intake decreased gradually with fish size up to approximately 200g of average body weight, and these values were remained relatively consistent afterward.

• Korean Journal of Veterinary Research
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• v.47 no.2
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• pp.241-245
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• 2007

Parallux (IDEXX Laboratories, USA), a solid-phase fluorescence immunoassay (SPFIA) developed for antibiotics residue detection in milk, was applied for analysis of antibiotics in muscle tissue of olive flounder (Paralichthys olivaceus), rockfish (Sebastes schlegeli), and red sea bream (Pagrus major). Fishes were dipped in streptomycin 20 g/ton water, the recommended therapeutic dose, for 3 consecutive days. Muscle was sampled after 1st, 2nd, 3rd, 4th and 5th day drug treatment. The concentration of streptomycin in muscle, determined by SPFIA, was compared with that of internal standard (200 ppb as streptomycin). The absorbance ratio of sample to internal standard (S/C) was employed as an index to determine the muscle residues in fishes. The standard solutions were added to muscle samples to give final concentrations in muscle of 0.2 and 0.5 mg/ml to investigate the recovery rate. The recovery rates of all spiked samples were > 84% of the spiked value. Streptomycin was detected in muscles of fishes treated after the 1st day of withdrawal period. The present study showed that the SPFIA can be easily adopted in predicting muscle tissue residues for streptomycin in farmed fishes.