• 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.21 no.4
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• pp.244-249
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• 2006

The residue depletion of amoxicillin was investigated in the olive flounder (Paralichthys olivaceus), rockfish (Sebastes schlegeli), and red sea bream (Pagrus major) after 7 days treatment with medicated feed at a dose of 400 mg/kg bw/day. Fishes were sampled for muscle on 1st, 2nd, 3rd, 4th, and 5th day after treatment. Amoxicillin concentrations were determined by high performance liquid chromatography with fluorescence detector. The recovery rates of amoxicillin in muscle samples ranged 84.3-101.3% and 75.0-91.5% for the concentration of 0.05 mg/kg and 0.1 mg/kg, respectively. Amoxicillin concentrations detected on 1st day after treatment were 0.137, 0.131, and 0.172 mg/kg in the muscle of olive flounder, rockfish, and red sea bream, respectively. After a withdrawal of 3 days, muscle concentrations were 0.012, 0.010, and 0.017 mg/kg in the olive flounder, rockfish, and red sea bream, respectively. Amoxicillin 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 amoxicillin is proposed on 4 days after 7 days treatment with medicated feed at a dose of 400 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 fish pathology
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• v.34 no.2
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• pp.213-224
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• 2021

Experiments were performed to investigate changes in metabolic rate (MO₂), critical oxygen saturation (S_crit) and hematological parameters of black rockfish, Sebastes schlegeli exposed to hypoxia at 15, 20 and 25℃. The MO₂ was measured at an interval of 10 min using intermittent-flow respirometry. The normoxic standard metabolic rate (SMR) was 116.5±5.5, 188.6±4.2 and 237.4±6.8 mg O₂/kg/hr, and S_crit was 22.1±1.2, 30.6±1.5 and 41.9±1.4% air saturation at 15, 20 and 25℃, respectively. Q₁₀ values were 2.62 between 15 and 20℃, 1.58 between 20 and 25℃, and 2.04 over the full temperature range. In the investigation of blood (hematocrit and hemoglobin) and biochemical parameters (plasma cortisol, glucose, electrolyte and osmolality), the rockfish were subjected to S_crit for each temperature during 4 hr. All of hematological parameters of the rockfish exposed to hypoxic water were significantly higher than those of normoxic control. Moreover, blood and biochemical parameters of the rockfish maintained to normoxic water showed the tendency of increase with temperature, and were significantly higher at 25C. As a result of this experiment, it was found that physiological stress due to hypoxia increased at high temperature.

• Journal of Aquaculture
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• v.10 no.2
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• pp.163-169
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• 1997

An experiment was conducted to determine the effects of feeding extruded-floating (EP), slow-sinking (SP), fast-sinking (FP) or moist (MP) prepared with two different levels of fish meal, respectively, on the growth, feed efficiency and body composition in Korean rockfish (Sebastes schlegeli). Triplicate groups of the 50 fish averaging 75g were fed each of the following diets : high fish meal (72% in diet)-EP, low fish meal SP, low fish meal-FP and low fish meal-MP for 15 weeks. Dietary fish meal levels or pellet types did not influence weight gain, feed efficiency and bo요 composition of the fish (P>0.05). Findings showed that each of EP, SP or FP can by used as a practical type of diet for Koran rockfish.

• Parasites, Hosts and Diseases
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• v.61 no.3
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• pp.332-337
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• 2023

Infestations of parasites, particularly those caused by copepods and monogeneans, are a major hindrance to aquaculture and have a big negative economic impact. Sebastes schlegelii, a farmed Korean rockfish, is particularly prone to copepods and monogeneans. This study comprehended how parasitic copepods and rockfish from a farm in Tongyeong-si, Gyeongsangnam-do, Korea, are related to the monogenean trematode Microcotyle sebastis. Our research revealed that monogeneans predominated, with a rate of 98.4% and an average infection intensity of 7 per infected fish. With an average infection intensity of 4 per sick fish, the infection rate for parasitic copepods was equally considerable, coming in at 91.7%. The high co-infection rate of both parasite families, at 90.8%, is noteworthy. Furthermore, Lepeophtheirus elegans and Peniculus truncatus, 2 parasitic copepod species, were discovered to have M. sebastis eggs attached to their bodies. This demonstrates a connection between parasitic copepod infestations in farmed Korean rockfish and the monogenean trematode M. sebastis. These discoveries highlight the necessity for creating more potent parasite control methods for the aquaculture sector and shed light on the intricate relationships between various parasite species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.6
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• pp.736-752
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• 1995

Fine structural changes of germ cell during the gametogenesis of Korean rockfish, Sebastes schlegeli sampled in west coast of Korea were investigated from September 1993 to August 1994. In a layer of microvilli of oocyte with active yolk duplication, many pinocytotic vesicles containing protein granules regarded as yolk precursors were observed. The multivesicular bodies were formed by gathered mitochondria. They are participated in formation of the primary yolk globules homogeneously filled with high dense particles and enclosed within a limiting membrane. The precursors of yolk globule appeared to be formed by modification of mitochondria and they developed into the primary yolk globules with participation of large and dense pinocytotic vesicles. Yolk globules in mature oocyte were consisted of three components: the crystalline type main body, the superficial layer with dense and fine granules, and the limiting membrane. Steroid hormone secreting cells were recognized in the interstitial cells of growing testis. Numerous endoplasmic reticula and large mitochondria with well developed tubular cristae appeared in their cytoplasms. The axoneme in the tail flagellum of spermatozoon consisted of nine pairs of microtubules at the periphery and one pair at the center, and they were covered with doublet microtubules.

• Parasites, Hosts and Diseases
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• v.59 no.1
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• pp.89-95
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• 2021

Microcotyle sebastis is a gill monogenean ectoparasite that causes serious problems in the mariculture of the Korean rockfish, Sebastes schlegelii. In this study, we isolated the parasite from fish farms along the coasts of Tongyeong, South Korea in 2016, and characterized its infection, morphology and molecular phylogeny. The prevalence of M. sebastis infection during the study period ranged from 46.7% to 96.7%, and the mean intensity was 2.3 to 31.4 ind./fish, indicating that the fish was constantly exposed to parasitic infections throughout the year. Morphological observations under light and scanning electron microscopes of the M. sebastis isolates in this study showed the typical characteristics of the anterior prohaptor and posterior opisthaptor of monogenean parasites. In phylogenetic trees reconstructed using the nuclear 28S ribosomal RNA gene and the mitochondrial cytochrome c oxidase I gene (cox1), they consistently clustered together with their congeneric species, and showed the closest phylogenetic relationships to M. caudata and M. kasago in the cox1 tree.

• Journal of fish pathology
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• v.36 no.2
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• pp.369-378
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• 2023

In this study, clinically healthy Korean rockfish were provided by a farm and then raised in a lab for 14 days at three different temperatures (10℃, 15℃, and 20℃) to establish hematological, blood biochemical, and histopathological reference intervals against normal fish. Hematocrit, MCV, MCHC, total protein, BUN, and GPT values in the blood showed significant differences among temperature groups. As the water temperature increased, neutrophil, thrombocyte, and lymphocyte counts also rose, while the monocyte value peaked at 15℃. The histopathological score revealed significant variations in the gills, stomach, and inflammation indices by temperature group; the gills and inflammation indices peaked at 20℃, whereas the stomach index peaked at 15℃. It is expected that information on these normal values will serve as a fundamental collection of data for further studies related to laboratory-based experiments.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.3
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• pp.394-399
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• 2017

To resolve environmental pollution caused by synthetic packaging materials, biodegradable films have been studied as an alternative. In this study, we prepared rockfish skin gelatin (RFG) and nano-clay (Cloisite $Na^+$ and Cloisite 10A) composite films to compare the effects of nano-clay on the physical properties of RFG film. Gelatin was extracted from rockfish skin and used to prepare RFG film with sorbitol as a plasticizer. Tensile strength (TS), water vapor permeability (WVP), and water solubility (WS) of the RFG film were 15.0 MPa, $2.70{\times}10^{-9}g\;m/m^2\;s\;Pa$, and 53.8%, respectively. Addition of nano-clay to the RFG film increased TS and decreased WVP and WS. The X-ray diffraction analysis and scanning electron microscopic results suggest that RFG/nano-clay composite films formed an exfoliated structure. These results indicate that RFG/nano-clay composite films can be applied as biodegradable packaging materials in the food industry.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.2
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• pp.129-136
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• 2005

The movement ranges and diurnal behavior of the rockfish (Sebastes schlegeli) sonic tagged externally were measured by the acoustic telemetry in the marine ranching area of Tongyoung on 20 to 26 March and 4 October to 3 November, 2003. The results of study are as follows: 1. Two cage cultured fishes (body length: $30-34{\cal}cm$) were released the point where located approximately $250{\cal}m$ from the caught point on 30 March, 2003. They moved to the south $500{\cal}m$ away Sojangdudo and stayed within a $500{\cal}m$ radius of the position during the study. 2. Three wild fishes (body length: $28-32{\cal}cm$) were released around the caught point on 4 and 8 October, 2003. It was often measured that tagged fishes moved out the $500{\cal}m$ radius of released point for a week after release. After several days, the movement range tended to be reduced. Finally, they stayed within the $250{\cal}m$ radius of released point. 3. There was no significant difference of diurnal behavior of the rockfish between the cage cultured and the wild fishes. The movement range, however, for the night-time was a little wider than for the day-time.