• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.2
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• pp.149-158
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• 2019

This study investigated the effects of replacing fish meal (FM) with a mixture of four protein sources (wheat gluten, soy protein concentrate, tankage meal, and poultry byproduct meal) in an extruded pellet (EP) diet for olive flounder Paralichthys olivaceus. Five experimental diets were formulated with alternative proteins replacing 0%, 20%, 30%, 40%, and 50% of FM. Taurine and betaine were added as attractants in the diets. Triplicate groups of fish (initial body weight: $196{\pm}2g$) were fed the diets to apparent satiation. Over the course of a 6-month feeding trial, there were no significant differences between the groups in growth performance, feed utilization, survival, or villus height. The dry matter and protein digestibility of FM50 diet were significantly lower than those of the control diet at water temperatures below $18.5^{\circ}C$ in months 4 and 6. This is a highly significant first report on FM replacement in an EP diet given to olive flounder over a 6-month-long feeding period. It shows that the proper mixture of protein sources can replace up to 50% of FM in olive flounder EP diets with taurine and betaine supplementation. It also shows that 40% of FM could be safely replaced in EP diets during periods of low water temperature.

• Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.153-162
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• 2021

In this study, a fish metabolic accelerator (a combination of butaphosphan and cyanocobalamin [BPC]) was injected into the muscle of the olive flounder, Paralichthys olivaceus, to investigate its effect on immunity and stress in fish maintained at low temperatures. A single dose of BPC was injected (100 mg/kg body weight) into the olive flounder, and its immunity and stress were observed after one and two weeks. Immunity tests revealed the presence of lysozyme (LZM), nitroblue tetrazolium (NBT), myeloperoxidase (MPO), anti-protease (AP), glutathione peroxidase (GPx), and total immunoglobulin (TIg). BPC injection was found to increase immunity activity compared to the control group. In particular, there was significantly high GPx activity. There was similarly high activity for MPO and GPx in the first week following the injection, followed by significant differences between the BPC-injected and control groups in the second week. There was a reduced low water-temperature stress response in the BPC-injected fish, as evidenced by the cortisol and glucose levels of the control and BPC groups. Lower levels were also observed in the BPC group than the control group during the second week. Cortisol levels were significantly lower in the BPC group than the control group. Histological examinations were conducted in the first and second weeks after the intramuscular injection of the recommended BPC dose to confirm the safety of BPC in aquaculture. There were no abnormalities observed in any tissue samples. This study confirms that the injection of BPC is safe even when used in a culture situation. BPC helps relieve stress and improves non-specific immune responses (innate immunity) in the olive flounder.

• Fisheries and Aquatic Sciences
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• v.24 no.2
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• pp.99-107
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• 2021

Water temperature (WT) is a major environmental factor of metabolic rate in fish; it directly affects food intake, ammonia excretion, oxygen consumption (OC), growth, and survival. Thus, the purpose of this study was to investigate changes in the OC and the hematological response of olive flounder Paralichthys olivaceus because of WT changes. In Exp. I, WT was increased from 20℃ to 29℃ within 18 h and maintained at 29℃ for 96 h. Then, WT was decreased from 29℃ to 20℃ within 18 h and maintained at 20℃ for 24 h. In Exp. II, WT was decreased from 20℃ to 11℃ within 18 h and maintained at 11℃ for 96 h. Then, WT was increased from 11℃ to 20℃ within 18 h and maintained at 20℃ for 24 h. The Exp. III maintained that the Exp. I and II was consecutively. In Exp. I, the OC increased from 116.7 mg O₂ kg^-1 hr^-1 to 317.5 mg O₂ kg^-1 hr^-1 with increasing WT. In Exp. II, the OC decreased from 96.5 mg O₂ kg^-1 hr^-1 to 71.3 mg O₂ kg^-1 hr^-1 with decreasing WT. In Exp. III, OC tended to increase or decrease in inverse proportion to temperature. In Exp. I, cortisol, glucose, and aspartate aminotransferase (AST) values increased with increasing WT. In Exp. II, Cl^-, osmolality, AST, and alanine aminotransferase (ALT) values significantly changed during the experimental period: glucose values increased, whereas cortisol values decreased with decreasing WT. Exp. III was shown to be a more stressful environment to olive flounder than Exp. I and Exp. II. The results of our study will be useful for evaluating current aquaculture procedures of olive flounder and developing techniques to minimize stress in aquaculture farms.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.3
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• pp.379-385
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• 2022

This study was conducted to evaluate the dietary supplementation of citrus byproduct (CBP) on the growth performance, feed utilization, and innate immune responses of juvenile olive flounder Paralichthys olivaceus under low water temperatures (11-15℃). Dietary L-ascorbyl-2-polyphosphate was replaced with graded CBP levels at 0 (Con), 25 (CBP25), 50 (CBP50), 75 (CBP75), and 100% (CBP100). Triplicate groups of juvenile olive flounder were handfed with one of the diets twice a day for 42 days. The growth performance and feed utilization of fish fed with diet containing levels of CBP75 or CBP100 increased significantly compared to those of fish with fed Con. Dietary CBP supplementation increased the protein efficiency ratio in fish. There was no significant differences in innate immune responses between groups, even though CBP supplementation tended to increase. These findings indicate that CBP could be used as a vitamin C source and improve the growth performance of juvenile olive flounder under low water temperatures.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.974-981
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• 2021

The aim of this study was to evaluate genetic parameters of growth traits for improving selective breeding in olive flounder Paralichthys olivaceus produced in April 2019. The total length and body weight at 11-, 18-, and 22-months-old were measured for 7,479, 2,831 and 1,904 individuals, respectively. Since 2004, we have been conducting a selective breeding program to improve growth traits in the olive flounder. Data were analyzed using the restricted maximum likelihood method using the multiple traits animal model. The effect of sex and production period showed significant differences in all traits (P<0.05). The heritability of all traits was 0.428-0.520, which is relatively high by measurement month. Therefore, it is considered that individual selection will be more advantageous than family selection. However, to maintain an appropriate degree of inbreeding and genetic diversity for future generations, it is necessary to consider family selection adequately. Results of the correlation analysis between the same traits according to the measurement period indicated that considering production costs such as feed cost, selection at 18-months-old will be advantageous. Olive flounder is a major aquaculture species in Korea, and continuous selective breeding research is essential to improve productivity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.533-540
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• 2022

We evaluated a worm-based extruded pellet diet with black soldier fly Hermetia illucens larvae (BSF) meal and BSF oil for olive flounder Paralichthys olivaceus through field feeding experiments at a commercial aquafarm. We prepared two experimental diets by replacing fish meal and fish oil with BSF meal and BSF oil (BEP-1, BSF meal 7%, BSF oil 1%) and (BEP-2, BSF oil 2%), respectively. We prepared raw-fish based moist pellets (MP) for comparison between the two experimental diets. We distributed the olive flounder (220±6.29 g) in square (10 m×10 m×1 m) concrete, 100 ton tanks at a density of 1,600 fish per tank (n=3) in triplicate for each dietary treatment. We fed the diets to the fish to apparent satiation for 7 months. At the end of the feeding trial, we found no substantial differences between the groups in terms of growth performance, survival, or feed utilization. None of the diet groups showed any changes in either hematological or non-specific immune responses. The histological observation of the intestine showed that the goblet cell number and cholecystokinin-producing cell activity increased in the fish fed the BEP diet compared with the those of the fish fed the MP diet. These results indicated that dietary BSF meal and oil can be used for olive flounder without compromising growth or, hematological and histological parameters.

• Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.243-249
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• 2022

Bacillus SW1-1 is a probiotic isolated from shrimp intestines. We investigated the effects of Bacillus SW1-1 coated diets on the growth, feed utilization, innate immunity, hematological parameters and resistance to Edwardsiella tarda in olive flounder (Paralichthys olivaceus). A commercial diet was used as the control (AP0) and two other diets were prepared by coating 0.25% (AP25) or 0.50% (AP50) probiotic powder which contains 1.0 × 10⁷ CFU/g Bacillus SW1-1. Four replicate groups of olive flounder (153 ± 2 g) were fed one of the diets for 12 weeks. Growth performance and feed utilization of the fish were not significantly affected by the dietary Bacillus SW1-1. After the challenge with E. tarda, AP50 group showed significantly higher survival than AP0 and AP25 groups. Innate immunity and anti-oxidant capacity of the fish were not significantly affected after the feeding trial. However, after the E. tarda challenge, the innate immune parameters (immunoglobulin, lysozyme and anti-protease) were significantly improved in fish fed AP25 and AP50 diets compared to those in fish fed AP0 diet. After the challenge test, significantly lower glucose level was observed in AP50 group compared to AP0 group. These results indicate that dietary supplementation of Bacillus SW1-1 could increase the disease resistance of olive flounder against E. tarda infection. The optimum coating levels of Bacillus SW1-1 needs to be further elucidated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.4
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• pp.532-540
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• 2023

This study aimed to evaluate the effects of dietary supplementation with two different types of hydrolyzed blood meal (HBM) on the growth performance, feed utilization, digestibility and innate immunity of olive flounder Paralichthys olivaceus. A control diet (Con) consisting of 60% fish meal was formulated and four diets containing two different types of HBM at varying concentrations were prepared 2.5 and 5.0% liquid HBM (L2.5 and L5.0) and 0.5 and 1.0% powdered HBM (P0.5 and P1.0). A total of 450 olive flounder (average body weight: 50±0.07 g) were distributed in 15 tanks (240 L), with three replicate groups per diet. The fish were fed the diets to apparent satiation for 9 weeks and subsequently exposed to Edwardsiella tarda. The results showed that fish fed L2.5, L5.0 and P0.5 diets exhibited significantly higher lysozyme activity compared to those fed the Con and P1.0 diets. During the challenge test against E. tarda, the L5.0 and P0.5 fish groups exhibited higher disease resistance than that of the Con group. These findings indicate that dietary supplementation with HBM could positively effect the innate immunity and disease resistance of olive flounder.

• Analytical Science and Technology
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• v.20 no.2
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• pp.170-175
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• 2007

To determine levels of benzopyrene in olive oils, a selective analytical method of HPLC/FLD has been applied. After removing fat in food samples with hexane, it was extracted in aqueous N,N-DMF solution, cleaned-up on florisil SPE cartridge and analyzed by the instrumental analysis. The mobile phase was a mixture of acetonitrile and water in 8:2 by the isocratic elution and the excitation wavelength of fluorescence detector was 294 nm and emission wavelength of it was 404 nm. The average recovery was about 95 % and the limit of quantitation was $0.9{\mu}g/kg$. The levels of benzopyrene in the selected olive oil samples were ranged from not detected to $1.9{\mu}g/kg$, however, they were under $2.0{\mu}g/kg$, the maximum level of benzopyrene in olive oil which was established in the food code.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.6
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• pp.930-935
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• 2023

This study aimed to analyze the structure of the value chain of the olive flounder aquaculture industry to increase the value of this industry. Based on the value chain theory, olive flounder aquaculture industry activities were classified as primary and support activities. The primary activities included seed production, fish production, producer distribution, consumer distribution, and consumption. The support activities were production infrastructure, organization and specialization, R&D, and government policy. A survey was conducted on the costs of seed and fish production in the primary activities to investigate the business structure, and the distribution structure was analyzed to examine distribution costs and margins. In the support activities, the recent trends in R&D and government policy were mainly examined, based on which, a measure to reduce costs and maximize profits was suggested. It is necessary to reduce costs across the production processes by improving seed quality and reducing labor, feed, and management costs, which are strongly associated with support activities. Therefore, lowering costs will be possible in the olive flounder aquaculture industry when R&D outcomes, such as species development, feed quality improvement, and aquaculture system development, are stably diffused and applied in tandem with government policy regarding the industry.