• Journal of Life Science
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• v.10 no.6
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• pp.548-557
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• 2000

A eight weeks feeding experiment was conducted to investigate the effects of different dietary dimethyl-$\beta$-propiothetin (DMPT) levels on growth and chemical components in Korean rockfish (Sebastes schlegeli). The content of DMPT extracted from Enteromorpha intestinalis by autoclaving was 31.1 mg%. Body weight gain and feed efficiency 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 contents of muscle was elevated in the DMPT added groups compared to control group. Amino acid composition of muscle in fish fed the diets supplemented DMPT was not different to that of control group. Fatty acid contents of muscle in fish increased with dietary DMPT level.

• Journal of fish pathology
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• v.11 no.1
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• pp.83-86
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• 1998

The benedeniine monogenean Benedenia derzhabini (Layman, 1930) Meserve, 1938 from cultured Korean rockfish, Sebastes schlegeli, is described and reported for the first time in Korea. The parasite was recovered from the gills and inner wall of operculum. B. derzhavini is distinguished from B. seriolae and B. sebastodis by the relative shape and length between the accessory sclerites and the hamuli.

• Korean Journal of Environmental Biology
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• v.22 no.3
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• pp.387-393
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• 2004

Experiments were carried out to investigate the lipid peroxidation (LPO), superoxide dismutase (SOD) activity and histopathological change of hepatic tissue for rockfish, Sebastes schlegeli after feeding sub-chronic dietary Benzo(a)pyrene (BaP) in the concentration of 0 (control), 0.5, 1.0, 1.5, 2.0 mg $kg^{-1}$ dry food of diet for 30 days. In 2.0 mg $kg^{-1}$ dry food group, the significant increase of LPO was observed in all period, and SOD activity was incresed at 30 days significantly in the same concentration. In the histological investigation of liver, there was the swelling of hepatic cells at 10 days over the 1.0 mg $kg^{-1}$ dry food concentration. At 30 days Periodic acid-Schiff (PAS) positive granule was observed in the same group and at 20 days was observed in 2.0 mg $kg^{-1}$ dry food group. And there was necrosis of hepatic cell in some fish of 2.0 mg $kg^{-1}$ dry food group at 30 days.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.3
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• pp.888-898
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• 2017

Tenebrio molitor larvae, also known as yellow mealworms (MW), are rich in protein and lipid and can serve as a potential alternative protein and energy source in commercial aquafeeds. Therefore, this study attempts to evaluate the effects of different drying methods on the nutritional value of MW meal. For this, live MW were cold-anaesthetized before being subjected to three different types of drying methods, including freeze-drying, oven-drying at $60^{\circ}C$ and air-drying at room temperature for three days, and compared for proximate composition and energy content. An in-vivo digestibility test was then conducted to evaluate the nutrient digestibility of MW meal in diets for rockfish, Sebastes schlegeli. A test diet was prepared by mixing the MW meal with a reference diet (Ref) in a 30:70 ratio with chromium oxide as an inert marker at the inclusion level of 0.5%. Rockfish with mean body weight of 150 g were stocked into a fecal collection system equipped with fiberglass tanks of 400 L capacity. Each group of fish was fed one of the experimental diets to apparent satiation for 4 weeks. The results of the proximate analysis showed that drying methods had no significant effect on crude protein, crude lipid, ash and energy contents of MW. Despite being a rich source of protein and lipid, MW meal was deficient in certain amino acids, particularly methionine, and highly unsaturated fatty acids, particularly 22:6n-3 (DHA) and 20:5n-3 (EPA). MW meal showed high digestibility values for protein (93%), lipid (97%) and energy (88%). These results may indicate that MW meal is a nutritious and acceptable feed ingredient, with comparable digestibility values to conventional animal and plant feedstuffs such as fish meal and soybean meal, in practical diet for rockfish at grower stage.

• Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.345-353
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• 2014

Copper has been widely used to control algae and pathogens in fish culture ponds. However, its toxic effects on fish depend not only on its concentration in the water but also on the water quality. A laboratory experiment was conducted to assess copper toxicity in the black rockfish Sebastes schlegeli using a panel of antioxidant enzymes, including glutathione (GSH), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase (SOD), at different levels of copper at three water temperatures (WT, 18, 23, $28^{\circ}C$) for 4 days. After exposure to two copper concentrations (100 and $200{\mu}g/L$), GSH levels and GST activities increased significantly, depending on WT (P < 0.05) in the liver, gill, and kidney of the black rockfish. GPx and SOD activities decreased significantly with both increasing WT and copper treatment in the organs of black rockfish (P < 0.05). These changes can be seen as initial responses to temperature stress and as a sustained response to copper exposure. This also indicates that GSH and related enzymes activities were sensitive indexes to stress by toxicants such as copper. The present findings suggest that simultaneous stress due to temperature change and copper exposure can accelerate changes in enzymes activities in the black rockfish. This provides another example of synergism between environmental temperature and pollutants, which may have important implications for the survival of fish in polluted environments during seasonal warming and/or global climate change.

• Fisheries and Aquatic Sciences
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• v.21 no.8
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• pp.29.1-29.8
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• 2018

This study was conducted to evaluate the use of tuna by-product meal (TBM) as a substitute for fishmeal in juvenile Korean rockfish (Sebastes schlegeli) diets. Five isonitrogenous (52% crude protein) and isocaloric (4.9 kcal/g) diets were prepared. Control diet (Con) was formulated to contain brown fishmeal, whereas 25, 50, 75, and 100% of fishmeal was substituted with the same percentage of TBM in the TBM25, TBM50, TBM75, and TBM100 diets, respectively. Three replicate groups of fish (initial weight, $29.5{\pm}0.6g$) were fed one of the five diets for 12 weeks. The mean weight gain of fish fed the Con and TBM25 diets was significantly higher than that of fish fed the TBM100 diet (P < 0.05), but it was not significantly different from the weight gain of fish fed the TBM50 and TBM75 diets. The feed efficiency and protein efficiency ratios of fish fed the Con diet were significantly higher than those of fish fed the TBM100 diet (P < 0.05), but were not significantly different from those fed the TBM25, TBM50, and TBM75 diets. The TBM25, TBM50, TBM75, and TBM100 diets had significantly (P < 0.05) lower incidence cost and higher profit index than the Con diet. These results suggest that the tuna by-product meal used in this study could replace up to 75% of fishmeal protein in the diet without reducing growth and feed utilization in juvenile Korean rockfish weighing 29-53 g. By considering feed cost, the TBM 75 diet is recommendable for Korean rockfish farming.

• Fisheries and Aquatic Sciences
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• v.1 no.2
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• pp.180-186
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• 1998

A 10-week feeding experiment was conducted to determine the phosphorus requirement of juvenile Korean rockfish (Sebastes schlegeli). Three replicate groups of fish initially averaging 4.2g were fed the semipurified experimental diets containing graded levels of $NaH_2PO_4\;\cdot\;2H_2O$ to provide from $0.1\%$ to $1.32\%$ total phosphorus level in a flow-through seawater system. Korean rockfish muscle and casein were used as the protein sources of the basal diet. Weight gain, feed efficiency and protein retention of fish fed the $0.35\%$ phosphorus were higher than those of fish fed the $0.1\%$ phosphorus, although no significant improvements $(P>0.01)$ were observed above the level. Determined phosphorus requirement using the broken line model was found to be $0.3\%$ for weight gain. Moisture, protein and lipid contents of whole body and muscle were not affected by dietary phosphorus levels $(P>0.01)$. Lipid contents of liver in fish fed the $0.1\%$ phosphorus were lower than those in fish fed the $0.35\%$ and $1.32\%$ phosphorus $(P<0.01)$. Dietary phosphorus increased ash and phosphorus contents of the whole body, while those of bone were not affected $(P>0.01)$. The data obtained in this study indicate that a $0.3\%$ dietaryphosphorus level could be recommended for the optimum growth and efficient nutrient utilization of juvenile Korean rockfish.

• Journal of Veterinary Clinics
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• v.23 no.3
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• pp.236-242
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• 2006

Along with olive flounder(Paralichthys olivaceus), black rockfish(Sebastes schlegeli) is another very popular maricultured species in Korea. As there is many difficulties in handlling live fish for aquaculturist, use of suitable anesthesia for proper handling of fish is very important in the field. In this view, the effect of $AQUI-S^{\circledR}$ has analysed for its use in the field. $AQUI-S^{\circledR}$, contains 50% isoeugenol, is a new anesthics for fish and zero-withdraw time required since it was approved as a safe additives of food. In the present study, black rockfish adult exhibted sedation effect from 5 ppm at $10^{\circ}C\;and\;15^{\circ}C$, and 7.5 ppm at $20^{\circ}C$, on the other hand, anesthesia was at least required 7.5 ppm at $10^{\circ}C\;and\;15^{\circ}C$, and 10 ppm at $20^{\circ}C$. The fish was recovered from sedation and anesthesia after approximately 5 and 10 minutes, respectively. In case of black rockfish fry, sedation was recorded from 2.5 ppm at $20^{\circ}C$, and 5 ppm at $15^{\circ}C\;and\;20^{\circ}C$. The least concentraion of anesthesia was 2.5 ppm at $10^{\circ}C$, 7.5 ppm at $15^{\circ}C$, and 5 ppm at $20^{\circ}C$. The acute toxic test showed that black rockfish adult and nv showed mortality above 12.5 and 15 ppm concentration of $AQUI-S^{\circledR}$, respectivly. In sum, $AQUI-S^{\circledR}$ is considered as useful anesthetic drug for sedation and anesthesia of black rockfish, it is highly availbale to be prevented from a varity of stress.

• Journal of Aquaculture
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• v.10 no.4
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• pp.387-394
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• 1997

A total of 353 farmed rockfish, Sebastes schlegli Hilgendorf, 1880 were sampled from 3 localities on Korean coastline over a 12 month period. Full parasitological examination revealed the polypisthocotylean monogenean Micorcotyle sebastis Goto, 1894 to be abundant with infections consistently reaching over 90~100% prevalence throughout the year. A seasonal pattern in parasite abundance on the gills is evident, with the population peaking twice, the largest in winter and again in summer. While the parasitic load on the left and right gills was not dissimilar, parasites within the gill sets were found to favour settlement of the II and III gill arches. A comparison of parasite abundance with host length, revealed that the smaller length fish classes (<17cm standard body length) had significantly heavier infections than those of larger fish (>17 cm standard body length). This report represents the fist record of Microcotyle sebastis on farmed rockfish in Korean coastal waters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.383-391
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• 1995

In order to find out the distribution of neuropeptide Y (NPY) recently known as the gonadotropin (GtH) stimulation neurohormone in the brain tissues of marine teleost, detection and localization of NPY like substance in brain of two rockfish species, Sebastes oblongus and S. schlekeli were done by immunohistochemisty. Distribution of GtH cells in hypophysis were also observed by aldehyde fuchsin (AF)-fast green-orange G stain to compare with gonadal phases of the rockfish species. NPY immunoreactive cells were detected in olfactory bulb, telencephalon and mesencephalon of the brain, and NPY immunoreactive fibers were distributed not only in olfactory bulb, telencephalon and mesencephalon but also in optic nerve, hypothalamus and optic tectum. Regardless of ovarian maturation in two rockfish species, NPY immunoreactive fibers were observed in the neurohypophysis adjacent to the AF negative cells in the rostral pars distalis of hypophysis in both species. Moreover, the fibers were distributed in the rostral and proximal pars distalis near to the GtH cells of the hypophysis in both species possessing the growing or mature oocytes. Slight AF stainable GtH cells were detected in hypophysis of two species before parturition (S. oblongus) and in mature stage (S. schlegeli), but AF stainability of the cells in the proximal pars distalis after parturition was more increased than that of the cells Tn mature stage or before parturition. The size and nucleus diameter of GtH cells in S. oblongus and S. schlegeli before parturition were significantly bigger than those of GtH cells in individuals after parturiton (S. oblongus) or with resting ovary (S. schlegeli) (P<0.01).