• Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.229-247
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• 2014

Seven feeding trials were conducted to determine the effects of feeding rate and frequency in the Korean rockfish Sebastes schlegeli at seven different water temperatures. Two feeding-rate experiments for 5-g Korean rockfish at $17^{\circ}C$ and $20^{\circ}C$; three feeding rate experiments for 16-g Korean rockfish at $16^{\circ}C$ and $24^{\circ}C$; and finally, two feeding frequency experiments for 93- and 100-g at $15^{\circ}C$ and $20^{\circ}C$ were conducted. Twenty fish averaging $5.5{\pm}0.2$ g ($mean{\pm}SD$) were randomly distributed into 18 indoor tanks containing 40-L seawater from a semi-recirculation system. Fish were fed a commercial diet for 4 weeks at water temperatures of $17^{\circ}C$ and $20^{\circ}C$. Two feeding trials were conducted to determine the optimum feeding frequency in growing Korean rockfish reared at temperatures of $15^{\circ}C$ and $19^{\circ}C$. Broken line regression analysis of weight gain (WG) indicated that the optimum feeding rates of 5-g growing Korean rockfish were 4.48% (BW/day; BW, body weight) at $17^{\circ}C$ and 4.83% (BW/day) at $20^{\circ}C$. Broken line regression analysis of WG showed optimum feeding rates of 16-g juvenile Korean rockfish of 3.41% (BW/day) at $16^{\circ}C$, 3.75% (BW/day) at $20^{\circ}C$, and 3.34% (BW/day) at $24^{\circ}C$. The biological performance, results, along with morphological indices and serological characteristics, suggest that a feeding frequency of 1 meal/day was optimal to improve WG in growing Korean rockfish grown from 93 to 133 g at a water temperature of $15^{\circ}C$, and 100 to 132 g at $19^{\circ}C$.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.9
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• pp.1319-1327
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• 2014

Two feeding trials were conducted to determine the optimum feeding frequency in growing Korean rockfish, (Sebastes schlegeli) reared at the temperatures of $15^{\circ}C$ and $19^{\circ}C$. Fish averaging $92.2{\pm}0.7$ g (mean${\pm}$standard deviation [SD]) at $15.0{\pm}0.5^{\circ}C$ and $100.2{\pm}0.4g$ ($mean{\pm}SD$) at $19.0{\pm}0.5^{\circ}C$ water temperature were randomly distributed into each of 15 indoor tanks containing 250-L sea water from a semi-recirculation system. A total of five feeding frequency groups were set up in three replicates as follows: one meal in a day at 08:00 hour, two meals a day at 08:00 and 17:00 hours, three meals a day at 08:00, 14:00, and 20:00 hours, four meals a day at 08:00, 12:00, 16:00, and 20:00 hours, and one meal every 2 days at 08:00 hour. Fish were fed at the rate of 1.2% body weight (BW)/d at $15^{\circ}C$ and 1.5% BW/d at $19^{\circ}C$. At the end of 8 wks of feeding trial weight gain and specific growth rate were significantly higher at the fish fed groups of one meal a day and two meals a day at $15^{\circ}C$ and fish fed groups of 1 meal every 2 days at $19^{\circ}C$ were significantly lower than those of all other fish fed groups. Glutamic oxaloacetic transaminase and glutamic pyruvic transaminase of fish fed group at 1 meal every 2 days was significantly higher than those of all other fish fed groups in both experiments. Weight gain, specific growth rate and condition factor were gradually decreased as the feeding frequency increased. The results indicate that growing Korean rockfish 92 and 100 g perform better at $15^{\circ}C$ than $19^{\circ}C$ water temperature. As we expected, current results have indicated that a feeding frequency of 1 meal a day is optimal for the improvement of weight gain in growing Korean rockfish grown from 92 g to 133 g at $15^{\circ}C$ and 100 g to 132 g at $19^{\circ}C$ water temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.4
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• pp.358-365
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• 2019

This study investigated the effects of dietary cactus Opuntia ficus-indica stem and fruit extract on the growth, flesh quality, lysozyme activity, and histological changes of growing Korean rockfish Sebastes schlegeli. Three replicates of fish (152 g/fish) were fed one of the following diets: containing 0 additions (control); 0.1, 0.5, or 1.0% cactus stem powder; or 1.0% fruit extract for 11 weeks. Growth performance did not differ significantly among treatments, including survival, final weight, feed efficiency, and daily feed intake. The experimental diets did not affect the proximate and fatty acid compositions, plasma biochemistry, or dorsal muscle texture of the fish. However, the plasma lysozyme activity of the fish fed the diet containing 0.1% cactus stem was significantly higher than that of the fish fed the control diet. These fish had variously sized lipid vacuoles in the liver tissue compared with the control. Distinct mucosal folds and mucus-secreting goblet cells developed in the fish fed the diet containing 1% cactus stem compared with the other dietary groups. These results suggest that feeding growing Korean rockfish cactus stem might increase the plasma lysozyme activity and induce histological changes in the gastrointestinal tract that might be related to digestion.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.777-784
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• 2013

This study compared the effects of diets consisting of experimental extruded pellets (EP), commercial soft extruded pellets (SEP), and raw-fish-based moist pellets (MP) on the growth, flesh quality, and histology of the Korean rockfish Sebastes schlegeli. Three replicated groups of 60 fish each (initial mean weight 152 g) were fed one of two experimental EPs (EP1 and EP2), two commercial SEPs (SEP1 and SEP2), or MP for 11 weeks. The survival, weight gain, and final mean weight of the fish did not differ significantly among the groups. The highest feed efficiency was in fish fed MP (P<0.05), and the protein efficiency ratio of fish fed MP was significantly higher than that of fish fed EP1, EP2, or SEP1, but not significantly different from that of fish fed EP2. The daily feed intake of the fish fed the EPs and SEPs was significantly higher than that of the fish fed MP (P<0.05). The condition factor, Hepatosomatic Index, and Viscerasomatic Index of the fish did not differ significantly among the groups. No notable differences in the textural properties of the dorsal muscle, plasma biochemical parameters, or histological features of the fish were observed in fish fed any diet. This suggests that extruded pellets can be used to feed growing Korean rockfish without compromising growth, flesh quality, or histopathological change in comparison to raw fish-based moist pellets.

• Proceedings of the Korean Aquaculture Society Conference
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• 2002.08a
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• pp.232-234
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• 2002

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.651-662
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• 1996

A 15-week growth trial was conducted in flow-through aquarium system to develop practical feeds for growing Korean rockfish. Two replicate groups of the fish averaging 114 g were fed one of nine diets containing $45\~50\%$ crude protein from various practical ingredients such as fish meal, meat meal, feather meal, blood meal, soybean meal, corn gluten meal, and wheat flour with or without supplemental essential amino acids (EAA) or enzyme mixture. The dietary EAA were adjusted by considering EAA composition of each dietary protein source, A/E ratio (each essential amino $acid\times1000/total$ essential amino arid including Cys and Tyr) calculated using Ah composition of the Korean rockfish whole body and the EAA requirement of other fish. Results indicate that animal and plant protein sources could substitute for fish meal up to $50\%$ in the diets, and the supplementation of amino acids and enzyme mixture have no beneficial effects on fish performance. Fish growth, body composition, nutrient utilization, and cost of fish production are discussed in relation to nutritional values of the protein sources used in diets.

• 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).

• Journal of Aquaculture
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• v.9 no.4
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• pp.377-384
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• 1996

A 15-week of growth trial was conducted to evaluate practical diets for growing Korean rockfish (Sebastes schlegeli). Two replicate groups of the fish average weighing 125 g were fed one of four experimental diets containing $41\~45\%$ protein and $6\~8\%$ lipid. A control diet with $58\%$ fish meal as protein source was included and practical form diets with $40\%$ fish meal and various practical ingredients such as meat meal, blood meal, soybean meal, and corn gluten meal were included. These experimental dry pellet diets were compared with commercial diets containing $51\~53\%$ protein and $5\~13\%$ lipid for marine fish or raw fish-based moist pellet (RMP) diet containing $58\%$ protein and $9\%$ lipid consisted of $50\%$ frozen horse mackerel and $50\%$ commercial binder meal. Weight gain, feed efficiency, daily feed intake and protein efficiency ratio in the fish fed the experimental diets and commercial diets were not significantly different to those in the fish fed the control diet. However weight gain, feed efficiency and protein efficiency ratio in the fish fed the RMP diet were significantly higher than those in the fish fed the experimental diets and commercial diets. These differences of growth performance between experimental diets and RMP diet may be reason for different dietary protein and energy levels. The experimental diet can save up to $20\%$ cost of fish production compare with control diet, whereas RMP diet is more expensive than other diets in the fish production.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.2
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• pp.135-142
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• 1996

Two experiments were conducted to investigate the utilization of various types of fish meal as dietary protein sources in Korean rockfish (Sebastes schlegeli). In the first experiment, averaging 5.7 g fish were divided into two groups and fed one of diets containing $55\%$ steam-dried white fish meal (SWFM) or $55\%$ brown fish meal (BFM) for 45 days. Weight gain and feed efficiency from fish fed SWFM were significantly (P<0.05) higher than those from fish fed BFM diet. However, daily feed intake, protein retention and lipid retention were not influenced by the two different diets. In the second experiment, averaging 86.6 g fish were divided into six groups and fed one of diets containing $56\%$ SWFM, $28\%\;SWFM+31\%$ flame-dried white fish meal (FWFM), $62\%\;FWFM,\;28\%\;SWFM+31\%\;BFM,\;56\%\;BFM$, or $28\%\;SWFM+29\%$ hydrolyzed fish protein (HFP) for 21 weeks. No significant differences were found among fish fed the six different diets in weight gain, feed efficiency, condition factor, whole body composition, and relative liver weight. Results of the present studies indicated that fish size should be considered in selecting feed ingredients and also feed cost could be lowered by replacing SWFM with FWFM or BFM in growing Korean rockfish diet.