• Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.7.1-7.8
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• 2020

Background: To minimize the use of antibiotics and to obtain a more sustainable fish culture and aquaculture industry, development of alternative natural source of immunostimulant to replace antibiotic in aquafeed is highly needed. Objective: Dietary inclusion effect of yacon (YC), ginger (GG), and blueberry (BB) on growth, body composition, and disease resistance of black rockfish against Vibrio anguillarum was compared to ethoxyquin (EQ). Methods: Four hundred eighty juvenile (an initial weight of 4.2 g) fish were randomly distributed into 12 of 50 L flowthrough tanks (forty fish per tank). Four experimental diets were prepared; the control (Con) diet with 0.01% EQ inclusion, and YC, GG, and BB diets at 1% each additive inclusion. Each additive was included into the experimental diets at the expense of wheat flour. Each diet was assigned to triplicate tanks of fish and hand-fed to satiation twice daily for 8 weeks. At the end of 8-week feeding trial, 20 fish from each tank fish were artificially infected by intraperitoneal injection with 0.1 mL of culture suspension of pathogenic V. anguillarum containing 3.3 × 10⁶ cfu/mL respectively. Fish were monitored for the following 8 days after V. anguillarum infection and dead fish were removed every 6 h for the first 4 days and 12 h for the rest of the study. Results: Weight gain, specific growth rate (SGR), and feed efficiency ratio (FER) of fish fed the YC diet was higher than those of fish fed all other diets. However, feed consumption, protein efficiency ratio, and protein retention was not affected by dietary additive. Moisture, crude protein, and crude lipid content of the whole body of fish were affected by dietary additive. Analysis of the Kaplan-Meier survival curves showed that survival of fish fed the YC, BB, and GG diets was higher than the Con diet. Conclusion: Oral administration of YC can improve not only weight gain, SGR, and FER of black rockfish, but lower mortality of rockfish at occurrence of V. anguillarum.

• Journal of fish pathology
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• v.11 no.1
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• pp.13-22
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• 1998

To know the features of Amyloodinium sp. parasitized in Black seabream, Acanthopagrus schlegeli, morphology and reproduction type of the parasite were investigated. Infection mode and histopathology of the parasites were also studied. In the developmental and morphological observation, the parasite passed through parasitic and non-parasitic phases with three developmental stages termed trophont, tomont, and dinospore. The trophont, 30-$80{\mu}m$ ovoidal or pyriform, for the vegetative stage had a spherical nucleus with $1.5{\mu}m$ in diameter, many food vacuoles and starch grains in cytoplasm. The tomont, 80-$90{\mu}m$ spherical, for the reproductive stage resorbed a stalk, secreted a cyst wall and reproduced within it. A dinospore, small 10-$15{\mu}m$ biflagellated, for the infestation stage had a stigma. The parasite was propagated for 15 days by serial passage in Korean rockfish (Sebastes schlegeli) at $25{\pm}1^{\circ}C$. Trophonts began to detach from the fish about 3 days after infection and was completed within 5 days at $25{\pm}1^{\circ}C$. It took from 3 to 5 days to reproduce at the same temperature. Reinfected fish showed that parasites penetrated under the epithelia of gill filament and gill lamellae causing hyperplasia and degeneration at infected area.

• 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).

• Fisheries and Aquatic Sciences
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• v.4 no.3
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• pp.112-119
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• 2001

Aim of this research is to investigate the effect of temperature shocks on the physiological responses of cultured olive flounder (Paralichthys olivaceus) and black rockfish (Sebastes schlegeli). Olive flounder and black rockfish were suffered with high and low temperature shocks for 4 and 8h, respectively, in laboratory conditions and then the changes in glucose, lactate, total protein, uric acid, and triglycerides-glycerol in blood plasma were analyzed. We observed that lactate and uric acid increased for up to 4h and then decreased for up to 8h by the high and low temperature shocks, and total protein decreased for up to 4h and then recovered for up to 8h by the high temperature shock in both fishes. Glucose by the high and low temperature shocks and triglycerides-glycerol by the low temperature shock increased for up to 4h, and then decreased in olive flounder, but increased for up to 8h in black rockfish. From the result, we speculated that the two fishes have an interspecific variation in the regulatory systems of glucose and triglycerides-glycero1. Glucose would play important role as an energy source during the temperature shocks and for an intermediate substance for low temperature tolerance, and glycerol of triglycerides-glycerol would play an important role for low temperature tolerance. In olive flounder, the turnover of chemical change by temperature shock took more than 4h, all chemicals returned almost to the initial level for up to 8h, but fish death followed only in 8h with the high temperature shocked group within two days. Therefore, we suggested that fish would be damaged severely by the longer time exposure of high temperature and mortality would occur after a certain time later than the shocked time as a post-effect.

• Journal of fish pathology
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• v.14 no.1
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• pp.21-30
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• 2001

From March 1998 to April 2000, 4 species of marine fishes including black rockfish (Sebastes schlegeli), goby (Acanthogobius flavimannus), fine-spooted flounder (Pleuronichthys cornutus), and croaker (Nibea albiflora) were captured from the coastal area of the Gogunsan island located in the mouth of the Kum River, and greenling (Hexagrammos otakii) was sampled from the coastal areas of the Gogunsan island and the Wan-do. Trematodes from the stomach and the intestine of the fishes were detected and identified on the basis of the morphological characteristics. Four species of trematodes were detected in the stomach and the intestine of the examined fishes ; Opecoelus lobatus Ozaki, 1925 from black rockfish, fine-spotted flounder and greenling, Coitoecum glandulosum Yamaguti, 1934 from goby, Phyllodistomum sp. Braun, 1899 from croaker, and Pharyngora sp. Lebour, 1908 from greenling captured from Wan-do. This report gave morphological descriptions of O. lobatus, Pharyngora sp. and Phyllodistomum sp. from coastal marine fishes in Korea.

• The Journal of Fisheries Business Administration
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• v.45 no.1
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• pp.95-107
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• 2014

This study is aimed to analyze the economic performance of black rockfish aquaculture by standardizing cost structures by region and farming size. The result of survey on farming and sale condition in each region, stocking density, survival rate, juvenile price, and unit production was the highest at Yeosu and Tongyeong, Heuksando showed the lowest. While rearing period was the longest at Tongyeong, the shortest region was Yeosu and Wando. In farming cost structure by region, amount of feeing was the highest at Tongyeong and Yeosu, and the lowest was Heuksando. Cost of medicine was high in Wando and Taean region, Yeosu and Hecksando was low. In case of farm size, feed cost ratio was high in the order of medium(0.75ha), small(0.25ha) and large(1.25ha) size. Standard production cost at every farm size of Heuksando showed the lowest among these regions. Taean and Yeosu was middle, and Tongyeong and Wando was the highest. According to the income, profit rate and investment return of farm size in all regions, as the bigger farm size, the higher income and profit rate was revealed. However, in case of Wando, Taean, and Heuksando which regions has high investment return, medium farm size was higher than large size. The result of economic analysis according to various factors, economic feasibility of black rockfish aquaculture in marine floating cage was showed significant changes by rearing and market condition.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.373-381
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• 1995

Oxygen consumption of marine fishes according to different water temperatures, fish population densities and body weights was measured in the respiratory chamber for the following six species: the olive flounder Paralichthys olivaceus, the tiger puffer Takifugu rubripes, the rockfish Sebastes schlegeli, the sea bass Lateolabrax Japonicus, the red seabream Pagrus major and the black seabream Acanthopagrus schlegeli. Also the lethal concentration of dissolved oxygen in them was determined. Oxygen consumption in each fish species increased as the water temperature increased. The relationship between the oxygen consumption rate $(Oc,\;ml/kg{\cdot}\;hr)$ and the water temperature (T,$^{\circ}C$) for each species appeared as the following equations demonstrate; olive flounder: Oc=34.0515T-339.5987 $(r^2=0.9730)$, tiger puffer: Oc=34.4941T-479.8732 $(r^2=0.9483),$ rockfish: Oc=44.7970T-634.2627 $(r^2=0.9718),$ sea bass: Oc=26.1488T-318.0633 $(r^2=0.9316),$ red seabream: Oc=61.1020T-722.8926 $(r^2= 0.9805),$ black seabream: Oc=75.1460T-947.9370 $(r^2=0.9392).$ The of gen consumption of fish with different population densities decreased as the number of fish increased. As the body weight of the olive flounder increased, the mass-specific oxygen consumption decreased. The relationship between oxygen consumption and body weight (W; g) was expressed as Oc=2532.0268W-0.6565 $(r^2=0.9229)$. The levels of lethal dissolved oxygen in the olive flounder, rockfish, tiger puffer and red seabream were 0.66, 0.79, 0.75 and 1.36 m1/1, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.119-128
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• 2002

This study investigates dorsal aspect target strength with fish size, tilt angle and frequency characteristics for the schlegel's black rockfish(Sebastes achlegeli) and the red seabream (Pagrus major). This study was carried out on free swimming fish in a cage in order to obtain acoustic data of the biomass estimation using the scientific echo sounder. The results obtained from this study are summarized as follows; 1 The coefficients of the schlegel's black rockfish and the red seabream using maximum TS with fish length were expressed -63.7dB and -62.6dB at a frequency of 38kHz, -64.4dB and -65.4dB at 120kHz, and -62.4dB and -65.0dB at 200kHz, respectively. 2. The coefficients of the schlegel\`s black rockfish and the red seabream using averaged TS with fish length were expressed -68.4dB and -67.9dB at a frequency of 38kHz, -73.4dB and -72.7dB at 120kHz, and -70.BdE and -73.4dB at 2001Hs, respectively. 3. The coefficients of the schlegel's black rockfish and the red seabream using maximum TS with body weight were expressed -52.0dB and -50.9dB at a frequency of 38kHz, -52.7dB and -53.7dB at 120kHz, and -50.7dB and -53.3dB at 200kHz, respectively. 4. The coefficients of the schlegel's black rockfish and the red seabream using averaged TS with body weight were expressed -56.7dB and -56.2dB at a frequency of 38kHz, -61.7dB and -61.0dB at 120kHz, and -59.ldE and -61.6dB at 200kHz, respectively. 5. Varying the tiIt angle of the two red seabream from -26$^{\circ}$to +25$^{\circ}$, the variation width of target strength expressed smaller at a frequency of 38kHz than at 120kHz and expressed about 3~6dB higher head up than head down at 120kHz.

• Journal of fish pathology
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• v.26 no.3
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• pp.173-183
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• 2013

From July to early September 2012, there was mass mortality of fishes, particularly black rockfish, which were being raised in the floating fish cage along the coast of Gyeongsangnam-do. The amount of damage was 1,802,000 fishes and the causes were confirmed to be rapidly rising water temperature and repeated daily changes in water temperature. The water temperature in this area of the sea rose to the maximum $28.4^{\circ}C$ and the daily range of changes in water temperature was maximum $6.5^{\circ}C$. As a result of investigating biological diseases of 194 fishes in 49 fishery areas, major pathogenic organisms such as red seabream iridovirus (RSIV), Vibrio sp. and Vibrio spp. or Microcotyle sp. were detected in rockfish in some fish farms. It is considered that the major causes of the mass mortality were high water temperature accompanied by repeated daily changes in water temperature, it is considered that biological diseases influenced the increase in the perish of fishes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.1
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• pp.20-25
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• 2008

The susceptibility of five different marine fish to iridovirus IVS-1 infection was analyzed and found a higher the cumulative mortality in the order of rock bream (Oplegnathus fasciatus), red sea bream (Pagrus major), sea perch (Lateolabrax sp.), rockfish (Sebastes schlegeli) and black porgy (Acanthopagrus schlegeli). However, the concentrations of virus in the infected spleens of these species did not differ significantly. To determine the release of iridovirus from infected fish into culturing seawater, rock bream were challenged with iridovirus IVS-1 and the concentration of virus in the water was analyzed using PCR. Over the 10 days of the analysis, the linear relationship between the number of dead fish and viral DNA concentration found in culturing seawater should be considered direct evidence of horizontal iridovirus transmission.