• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.577-582
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• 2020

This study was conducted to investigate the replacement of fish meal (FM) with a plant and animal protein mixture (wheat gluten, soy protein concentrate, tankage meal and poultry by-product meal) in the diets of juvenile olive flounder Paralichthys olivaceus. The basal diet was formulated to contain 65% FM (Con). Four other experimental diets were formulated with alternative proteins replacing 20%, 30%, 40% and 50% of FM (FM20, FM30, FM40 and FM50, respectively). Taurine and betaine were added to the FM replacement diets. Triplicate groups of fish (mean±SD, 5.41±0.01) were fed the diets to apparent satiation for 15 weeks. After the feeding trial, no significant differences were found between any dietary groups in growth performance, feed utilization, survival, hematological parameters or whole-body composition. This result indicates that a proper mixture of the four protein sources with taurine and betaine supplements can be used as FM replacement to reduce FM levels from 65% to 32.5% in juvenile olive flounder diets.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.3
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• pp.314-321
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• 2015

We performed three sets of feeding trials to establish the optimal feed size (Exp-I), stocking density (Exp-II), and dissolved oxygen level (DO) (Exp-III) for olive flounder Paralichthys olivaceus. In Exp-1, four replicate groups of fish ($53.6{\pm}0.9g$) were fed commercial diets with three particle sizes (small, medium, and large). In Exp-II, fish ($30.0{\pm}0.1g$) were reared at four stocking densities (1.8, 3.5, 5.3, and $7.1kg/m^3$). In Exp-III, fish ($187{\pm}1.48g$) were reared under two different DO levels (2-3 and 6-7 mg/L). In Exp-I, fish fed the large-particle diet gained significantly more weight and had a lower feed conversion ratio than fish fed the small- and medium-particle diets. In Exp-II, fish reared at 1.8 and $3.5kg/m^3$ gained slightly more weight and had lower feed conversion ratios than fish reared at 5.3 and $7.1kg/m^3$, although these differences were not significant. In Exp-III, negative effects were observed in the low DO groups. Therefore, under our experimental conditions, the optimal feed particle size, stocking density, and DO level for olive flounder were 9-9.4 mm, $3.5kg/m^3$, and 6-7 mg/L, respectively.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.4
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• pp.373-379
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• 2023

The dietary inclusion of black soldier fly larvae meal Hermetia illucens (BSL) for starry flounder Platichthys stellatus was examined in a four-month trial at a Pohang fish farm. Two diets were prepared: a fish meal-based commercial diet (CD) and an experimental diet containing 7% BSL in the CD (BCD). Fish (average weight, 125.2 g) were reared in a square concrete tank (7×7 m) in triplicates. Feed efficiency was significantly higher in fish fed BCD compared to that of the fish fed CD. The DHA/EPA ratio in dorsal muscle was not significantly affected by the fatty acid composition of the experimental diets. Based on the growth performance, the feed cost for producing 1 kg of starry flounder was 1,797 won for CD and 1,814 won for BCD. With government subsidies the feed cost for producing 1 kg of starry flounder was 1,481 won for CD and 1,309 won for BCD. The results indicate that BSL can be included at 7% without adverse effects on growth performance, fillet composition, or feed cost. However, further research is needed to determine the optimum percentage of BSL as a replacement of FM in starry flounder diets.

• Journal of Microbiology and Biotechnology
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• v.33 no.10
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• pp.1390-1401
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• 2023

In this study, a 12-week feeding experiment was conducted to characterize the effects of exogenous α-amylase on the growth, feed utilization, digestibility, plasma α-amylase activity, feed degradation rate, and fecal particle size of olive flounder (Paralichthys olivaceus). Diet was supplemented with 0 (AA₀; control), 100 (AA₁₀₀), 200 (AA₂₀₀), or 400 (AA₄₀₀) mg/kg of α-amylase, respectively. Fish (273.1 ± 2.3 g) were stocked into 12 tanks (25 fish/1,000-L tank) and 3 tanks were randomly selected for each diet group. As a result, α-amylase was found to have no significant effects (p ≥ 0.05) on the growth, feed utilization parameters, and whole-body proximate compositions. α-Amylase-treated fish exhibited only a significant increase in the apparent digestibility coefficient of carbohydrates compared to the controls. In addition, in vitro analyses revealed that α-amylase dose-dependently increased (p < 0.05) the feed degradation rate, while photographs of the intestinal content after 2, 4, and 8 h of feeding demonstrated an improved degradation rate in the α-amylase-treated groups. Plasma α-amylase content was higher in the AA₂₀₀ and AA₄₀₀ groups, whereas the control group produced significantly larger-sized fecal particles (90% size class) than these two groups. In the intestine, no changes were observed in the expression levels of the immune-related TNF-α, IL-1β, IL-2, immunoglobulin-M, HSP-70, lysozyme, and amylase alpha-2A. However, growth-related genes IGF-1, IGF-2, TGF-β3, and growth hormone genes were upregulated in muscle tissues. Collectively, exogenous α-amylase has positive roles in the modulation of the digestibility coefficient, blood α-amylase concentration, growth-related gene expression, and diet degradation for improved digestion in olive flounder.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.3
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• pp.234-240
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• 2014

We investigated the effects of feeding rate on the growth performance, blood components, and histology of growing olive flounder Paralichthys olivaceus. We determined the optimum feeding rate (initial fish mean weight of $240{\pm}10.9$ g) at the optimum water temperature. Two replicated groups of fish were fed a commercial diet at rates of 0%, 0.5%, 0.75%, and 1.0% body weight (BW) per day, and to satiation. Feeding trial was conducted using a flow-through system with 10 1.2-metric ton aquaria receiving filtered seawater at $19-21^{\circ}C$ for three weeks. Weight gain (WG) for fish fed to satiation was significantly higher than that of unfed fish and fish fed at 0.5% and 0.75% BW per day. The WG of fish fed at 1.0% BW per day was significantly higher than that of unfed fish and of fish fed at 0.5% BW per day. However, there were no significant differences in WG between fish fed at 0.5% BW per day and those fed at 0.75% BW per day, between fish fed at 0.75% BW per day and those fed at 1.0% BW per day, and between fish fed at 1.0% BW per day and those fed to satiation. The specific growth rates of fish fed at 1.0% BW per day and those fed to satiation were significantly higher than those of unfed fish and of fish fed at 0.5% BW per day. Broken-line regression analysis of weight gain showed that the optimum feeding rate of olive flounder weighing 240 g was 1.09% BW per day at the optimum water temperature.

• Journal of Aquaculture
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• v.21 no.2
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• pp.102-106
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• 2008

This study was conducted to evaluate extruded pellets(EP) for the growth of sub-adult flounder Paralichthys olivaceus by comparing with raw fish-based moist pellet(MP). Two replicate groups of 150 fish per each tank(initial mean weight $594{\pm}6.5g$) were fed one of two EPs(EP1 and EP2) and a MP for 32 weeks. Survival was not significantly affected by experimental diets. Final mean weight of fish fed the EP1 was not significantly different from that of fish fed the MP, but that of fish fed EP2 was significantly lower than that of fish fed EP1 and MP (P<0.05). Feed efficiency and protein efficiency ratio of fish fed the EP1 and EP2 were significantly higher than those of fish fed MP(P<0.05). Daily feed intake of fish fed the EPs was significantly lower than that of fish fed MP(P<0.05). Condition factor was not significantly different among all groups. The contents of moisture, crude protein and lipid in dorsal muscle were significantly affected by experimental diets(P<0.05). Based on the results of this study, the dietary formulations used in EP1 and EP2 could be applied in the practical extruded pellet feeds for sub-adult flounder(594-1,126 g).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.606-611
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• 2012

This study examined the effects of dietary glycoprotein extracted from Porphyra yezoensi on growth performance and resistance against the pathogenic bacteria Edwardsiella tarda in olive flounder. A porphyra-originated glycoprotein (P) was extracted using sequential processes of water and ethanol treatment. P extracts were added to a fish-meal-based diet at concentrations of 0.0, 0.5, and 1.0% (designated as Con, $P_{0.5}$, and $P_{1.0}$, respectively). Fish were fed one of the three experimental diets for 10 weeks. All fish groups exhibited over 96.7% survival during the experimental period. Results indicated that the fish fed diets containing P showed an increase in growth performance, including enhanced weight gain, specific growth rate, and feed efficiency. An increase in insulin-like growth factor (IGF-1) was observed in the fish fed the $P_{1.0}$ diet, as compared to those fed Con. At the end of the 10-week feeding trial, all fish were infected with E. tarda, and accumulated mortality was monitored for 8 days. Fish fed the Con diet exhibited increasing mortality from day 3 to the end of the challenge test, whereas the mortality of P-fed fish ceased at day 5. We suggest that supplementation with P-originated glycoprotein in aquafeed may increase growth performance and resistance against pathogenic bacteria in olive flounder juveniles.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.4
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• pp.345-351
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• 2011

Two feeding trials were conducted to investigate the optimum feeding rates in juvenile olive founder Paralichthys olivaceus fed practical expanded pellet(EP) containing 58.1% crude protein, 10.7% crude lipid, and 10.8% ash at low and high water temperatures. In the first experiment, triplicate groups of 15 fish with average weight of 7.7 g were fed at one of seven feeding rates(0, 1, 1.5, 2, 2.25, or 2.5% of body weight/day or to satiation) for 4 weeks at low water temperature. In the second experiment, quadruplicate groups of 20 fish with average weight of 5.5 g were fed at one of eight feeding rates(0, 3, 3.5, 4, 4.25, 4.5, or 4.75% of body weight/day or to satiation) for 4 weeks at high water temperature. Based on growth performance, we estimated that the optimum feeding rates for juvenile olive flounder were 1.97-2.51% and 4.82-6.36% of body weight/day at low and high water temperatures, respectively.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1433-1442
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• 2018

To identify and quantify the effects of a combination of dietary $1{\times}10^8CFU/g$ Lactococcus lactis subsp. lactis I2 ($LI_2$) and 0.1% ${\beta}$-glucooligosaccharides (BGO) on the growth and immunity of olive flounder (Paralichthys olivaceus), a feeding experiment was conducted. Flounder ($14{\pm}0.5g$) were divided into two groups and fed control and synbiotic feeds for 8 weeks. Investigations were carried out on growth and feed utilization, innate immunity, serum biochemical parameters, intestinal lactic acid bacterial (LAB) viability, microvillus length, and changes in the expression levels of genes encoding pro-inflammatory cytokines (tumor necrosis factor $[TNF]-{\alpha}$, interleukin $[IL]-1{\beta}$, and IL-6). Results demonstrated the synbiotic diet had significantly better (p < 0.05) responses in terms of weight gain and specific growth rate, three innate immune parameters (respiratory burst, serum lysozyme, and superoxide dismutase), intestinal LAB viability, and the relative $TNF-{\alpha}$ expression level (p < 0.05). Moreover, after challenge with Streptococcus iniae ($1{\times}10^8CFU/ml$), the synbiotically fed group exhibited significantly higher (p < 0.05) protection against streptococcosis, validating the observed changes in immune parameters and induction of the cytokine-encoding gene. Therefore, according to the results of the present study, synbiotic feed ($LI_2+BGO$) increased growth, modulated innate immune parameters and protected olive flounder against streptococcosis.