Growth Of Flounder Research Articles

Stable cell-surface expression of Japanese flounder growth hormone in yeast Saccharomyces cerevisiae and growth-promoting effect on juvenile fish by oral administration

A cost-effective method for producing and using recombinant growth hormone (GH) has been developed. A cell-surface protein display system was constructed to produce recombinant Japanese flounder growth hormone (r-JfGH) in yeast Saccharomyces cerevisiae and the biological activity of expressed r-JfGH was evaluated by oral delivery to juvenile Japanese flounder. The expression vector pYD-E2, containing the JfGH gene, S. cerevisiae GAL1 promoter, and the S.cerevisiae URA3 gene downstream and upstream sequences, was designed and constructed to integrate the GH gene into the yeast genome and secrete r-JfGH stably on the surface of the yeast cell. Expression of r-JfGH was confirmed by flow cytometry until the 50th continuous generation of transgenic yeast strain y-E2, and over 0.98 μg r-JfGH per 1 mg total protein of y-E2 was estimated by an ELISA–RA assay. Growth of Japanese flounder was promoted significantly by the direct supplementation of freeze-dried transgenic yeast into the Japanese flounder juvenile feed at levels of 0.5 and 1%. The weight-specific growth rate and feed conversion ratio of the treated groups were 23.07 and 21.57% (0.5% feeding level) and 28.85 and 41.18% (1% feeding level), respectively, higher than that of the control group in a 7-week bioactivity study.

Estimates of genetic and phenotypic parameters for weight and length in Paralichthys olivaceus (Temminck et Schlegel)

The complete diallel cross design was employed to estimate the genetic parameters of the growth of Japanese flounder (Paralichthys olivaceus). A total of 60 full-sib families were cultivated and two growth-related traits, body weight (BW) and body length (BL), were examined at average 2, 3 and 8 months of age respectively, with 1 800 individuals measured in each age group (30 per family). Based on the additive-dominance-maternal-effect genetic analysis model, the restricted maximum likelihood approach was used to estimate various (co)variance components. The results showed that narrow-sense heritability estimates of BW and BL were respectively: 0.29±0.01 and 0.22±0.02 at 2 months of age, 0.32±0.02 and 0.30±0.04 at 3 months of age, 0.48±0.04 and 0.40±0.05 at 8 months of age; broad-sense heritability estimates were respectively: 0.44±0.02 and 0.54±0.04 at 2 months of age, 0.35±0.01 and 0.36±0.03 at 3 months of age, 0.49±0.03 and 0.45±0.04. All heritabilities were statistically significant (P <0.05). Additive genetic correlations between BW and BL at 2, 3 and 8 months of age were consistently positive and highly significant (P <0.01): 0.93±0.02, 0.95±0.03 and 0.92±0.03 respectively. Maternal effect was significant (P <0.05) only at 2 months of age, and was not detected at 3 and 8 months of age. According to the heritability estimates, the mass selection strategy should be efficient for the breeding of Japanese flounder.

Effect of dietary fish protein hydrolysate on growth, feed utilization and IGF-I levels of Japanese flounder (Paralichthys olivaceus)

This study was conducted to investigate the effect of fish protein hydrolysate on growth performance, insulin-like growth factor I (IGF-I) levels and the expression levels of liver IGF-I mRNA in juvenile Japanese flounder (Paralichthys olivaceus). Fish hydrolysate was produced by enzymatic (alcalase and flavourzyme) treatment and size-fractionated by ultrafiltration. The permeate after ultrafiltration (UF) and the non-ultrafiltered fish hydrolysate were tested as feed ingredients using high plant protein diets. Fish meal was used in the control diet (FM). The feeding trial lasted for 60 days, and fish fed with 37 g kg−1 UF showed the best growth, feed efficiency, digestibility and protein utilization. Plasma IGF-I level was examined with radioimmunoassay, and the expression levels of liver IGF-I mRNA were evaluated using real-time PCR normalized against the 18S rRNA gene. Plasma IGF-I levels were significantly increased by inclusion of fish protein hydrolysate. Liver IGF-I mRNA expression was significantly higher in fish fed with 37 g kg−1 UF diet than fish fed with control diet. The results indicated that small molecular weight compounds from fish protein hydrolysate showed a positive effect on growth and feed utilization in juvenile Japanese flounder. Dietary fish protein hydrolysate could improve plasma IGF-I levels and liver IGF-I mRNA expression in Japanese flounder.

Response of dietary substitution of fishmeal with various protein sources on growth, body composition and blood chemistry of olive flounder (Paralichthys olivaceus, Temminck &amp; Schlegel, 1846)

Animal and/or plant protein sources substituting fishmeal in the diets keep being developed due to its high price. The purpose of this study is to determine response of dietary substitution of fishmeal with silkworm pupae meal, promate meal®, meat and bone meal and/or their combination on the performance of juvenile olive flounder. A 60% fish meal was used as the main protein source, used as the control (Con) diet. The 10 and 20% fishmeal were substituted with silkworm pupae meal and meat and bone meal, referred to as the SPM10, SPM20, MBM10 and MBM20 diets, respectively. And the 10, 20 and 40% fishmeal were substituted with promate meal®, referred to as the PM10, PM20 and PM40 diets, respectively. Finally, the 10 and 20% fishmeal were substituted with combined silkworm pupae meal and promate meal®, refereed to as the SPM + PM10 and SPM + PM20 diets, respectively. Weight gain and specific growth rate of fish fed the MBM10 diet were higher than those of fish fed the Con, SPM20, PM20, PM40 and SPM + PM20 diets. Feed efficiency ratio of fish fed the SPM10, MBM10, MBM20, PM10 and SPM + PM10 diets was higher than that of fish fed the SPM + PM20 and PM40 diets. Protein efficiency ratio of fish fed the MBM10 and MBM20 diets was higher than that of fish fed the SPM20, PM20, PM40 and SPM + PM20 diets. In conclusion, dietary substitution of fishmeal with 10% SPM, 20% MBM, 10% PM and 10% SPM + PM could be made.

Trophic Ecology of Summer Flounder in Lower Chesapeake Bay Inferred from Stomach Content and Stable Isotope Analyses

AbstractTrophic studies of summer flounder Paralichthys dentatus have relied on traditional stomach content analyses to infer contributions of prey to species productivity. We applied both stable isotope and stomach content analyses to identify prey groups that are responsible for summer flounder productivity in lower Chesapeake Bay and to explore ontogenetic patterns in prey utilization. Summer flounder (total length = 138–682 mm; age = 0–11 years) were collected for stomach and tissue samples (liver, blood, and muscle) during spring–summer (May–July) and fall (November) of 2006 and 2007. Commonly consumed crustacean and fish prey species were also collected: mysid shrimp Neomysis americana, sevenspine bay shrimp Crangon septemspinosa, mantis shrimp Squilla empusa, bay anchovy Anchoa mitchilli, spotted hake Urophycis regia, and juvenile sciaenids. Analysis of the nitrogen stable isotope ratio (δ15N; ratio of 15N to 14N relative to a standard) revealed that crustaceans comprised the majority (72–100% on average) of the summer flounder diet except in spring 2006, when fish consumption was more dominant. Analysis of corresponding stomach contents indicated a lower contribution of crustacean prey. Based on isotopes, summer flounder tended to occupy the same trophic level as the prey fishes. The δ15N in all tissues exhibited a positive trend with body length, indicating that larger summer flounder fed at approximately one trophic level above smaller individuals; the positive trend also corresponded with increasing proportions of fish in summer flounder stomachs. Our stable isotope analysis indicates that growth and production of summer flounder in lower Chesapeake Bay are highly dependent on assimilation of mysid shrimp, sevenspine bay shrimp, and mantis shrimp—more so than previously expected based on stomach content research.

어분 종류 및 소맥분 함량이 다른 배합사료가 넙치 (Paralichthys olivaceus)의 성장과 소화율에 미치는 영향

A feeding trial was carried out to investigate the effect of different fish meal and wheat flour contents in extruded pellets on the growth and apparent nutrient digestibility of olive flounder Paralichthys olivaceus. Four extruded pellets (HB1, HB1T, HB2 and HB2T) were prepared using two kinds of high quality brown fish meal and low quality tuna fish meal. Two diets (HB1 and HB2) contained two different kinds of brown fish meal, respectively; in HB1T and HB2T, we substituted 50 % of the brown fish meal with 10 % wheat flour. Three replicate groups of fish (initial body weight of 82 g) were fed the experimental pellets to visual satiation for 15 weeks. The highest weight gain was observed in fish fed HB1, and weight gain of fish fed HB2 was significantly higher than that of fish fed HB2T (P<0.05). Feeding efficiency for fish fed HB1 was significantly higher than that of fish fed HB1T and HB2T (P<0.05), but was not significantly different from fish fed HB2. Apparent dry matter digestibility in HB1 and HB2 was significantly higher than in HB1T and HB2T (P<0.05). The highest crude protein digestibility was observed in HB1, and protein digestibility in HB1T and HB2 was higher than in HB2T (P<0.05). The results of this study suggest that fish meal quality considerably affects growth and nutrient digestibility of olive flounder fed extruded pellets, and the use of HB1 is recommended over HB1T, HB2 and HB2T for efficient olive flounder production.

Effects of the Dietary Moisture Levels and Feeding Rate on the Growth and Gastric Evacuation of Young Olive Flounder Paralichthys olivaceus

This study determined the effects of the dietary moisture level and feeding rate on the growth and gastric evacuation of young olive flounder. Four experimental diets with different moisture levels (9%, 21%, 30%, and 40%) were prepared through the addition of water to the commercial extruded pellet. Three replicate groups of fish (initial weight: <TEX>$106{\pm}1.4\;g$</TEX>) were fed diets containing 9%, 21%, 30%, and 40% moisture to satiation or a moisture level of 9% and 30% at a restricted feeding rate (95% of satiation) for 15 weeks. The mean water temperature was <TEX>$22{\pm}1.6^{\circ}C$</TEX> during the feeding trial. Gastric evacuation rates were determined post-feeding. The dietary moisture levels did not significantly affect weight gain, but the weight of the fish receiving 9% and 30% moisture diets to 95% satiation were significantly lower than those of the fish fed 9-40% moisture diets to 100% satiation (P<0.05). The feed efficiency, protein efficiency ratio, viscerosomatic index, and survival were not significantly affected by the dietary moisture levels and feeding rates. The daily feed intake of the fish fed to 100% satiation did not significantly differ among the treatment groups. The stomach contents that peaked within 3 h of feeding gradually decreased, and the stomachs of fish were completely evacuated within 18 h. The contents of the intestine peaked at 3-12 h post-feeding, and then declined with the intestine being mostly evacuated at 30 h. The moisture of the stomach contents reached approximately 70% within 3 h post-feeding and gradually increased to approximately 75% within 12 h. No considerable differences were observed in the gastric evacuation and moisture levels of the stomach contents in the fish fed the different diets. The results of this study suggest that the gastric evacuation of olive flounder was not affected by the dietary moisture level and that the addition of water into the diet displayed no beneficial effects on the growth of young olive flounder.

Effects of dietary protein sources on feed intake, growth and plasma thyroid hormones levels of Japanese flounder (Paralichthys olivaceus)

An 8-week feeding trial was conducted to compare the effects of dietary protein sources on growth performance and plasma thyroid hormones levels of Japanese flounder Paralichthys olivaceus. Four isonitrogenous and isoenergetic diets were formulated to contain one of the followings as main protein source: fish meal (FM), fish protein concentrate (FPC), soy protein concentrate (SPC), and soy protein isolate (SPI). Each diet was randomly assigned to triplicate aquaria stocked with 25 fish each. The feed intake, specific growth rate, feed efficiency, and protein efficiency ratio in fish fed fish protein-based diets were significantly higher than those in fish fed soy protein-based diets. Feed intake and specific growth rate were significantly higher in FM treatment compared to FPC treatment and higher in SPI treatment compared to SPC treatment. The FM treatment had significantly higher levels of plasma cortisol, triiodothyronine, and thyroxin than the other treatments. These results indicate that high inclusion levels of soy protein in diets markedly inhibit the feeding rate and growth of P. olivaceus due to poor palatability caused by the removal of feeding stimulants and/or the incorporation of feeding deterrents. The reduced growth may be partly attributed to the amino acid imbalance, absence of small nitrogen compounds, and presence of antinutritional factors.

배합사료의 수분 함량이 여름 및 겨울철에 사육된 미성어기 넙치(Paralichthys olivaceus)의 성장 및 소화관내 사료 통과 시간에 미치는 영향

Two experiments were conducted to investigate the effects of dietary moisture content on the growth and gastrointestinal evacuation of sub-adult olive flounder (Paralichthys olivaceus) in the summer and winter seasons. In the first experiment, three experimental diets containing different moisture levels (7%, 15%) and additives were prepared by adding water and commercial additives (1% nutrients, 1% digestives) to commercial extruded pellets. Fish (initial weight: <TEX>$332{\pm}9.2$</TEX> g) were distributed randomly into six 3000 L tanks (25 fish/tank) in a flow-through tank system. Two replicate groups of fish were fed the experimental diets to satiation for 14 weeks during the summer season (<TEX>$21.4{\pm}2.5^{\circ}C$</TEX>). Survival, weight gain, feed efficiency, and daily feed intake did not differ significantly among groups. In the second experiment, two experimental diets containing different moisture levels (8%, 23%) were prepared by adding water to commercial extruded pellets. Fish (initial weight: <TEX>$646{\pm}6.7$</TEX> g) were randomly distributed into six 3000 L tanks (20 fish/tank) in a flow-through tank system. Three replicate groups of fish were fed the experimental diets to satiation for 19 weeks during the winter season (<TEX>$12.2{\pm}1.2^{\circ}C$</TEX>). Weight gain, feed efficiency, and daily feed intake did not differ significantly among groups. Gastrointestinal evacuation rates were determined after the end of the winter feeding trials. The stomach contents of fish fed diets containing different moisture levels peaked within 3 h after feeding and then decreased gradually over 40 h to approach pre-feeding levels. Intestinal contents began to accumulate 3 h after feeding and reached a maximum at 32 h, then declined until nearly complete evacuation around 56 h. The stomach contents reached moisture levels of approximately 70% within 3 h after feeding and then increased gradually. No considerable difference in moisture levels was observed in the stomach contents of fish fed diets with different moisture contents. The results of this study suggest that the gastric evacuation of sub-adult olive flounder was not affected by dietary moisture level and the addition of water to the diet had no beneficial effect on the growth of sub-adult olive flounder in the summer and winter seasons.

Effect of Intermittent Feeding on Growth, Feed Utilization and Body Composition of Subadult Olive Flounder Paralichthys olivaceus in Suboptimal Temperature

The effect of intermittent feeding on growth, feed utilization and body composition of subadult olive flounder fed extruded pellet (EP) in suboptimal temperature () was determined. Two hundred twenty five subadult fish averaging 272 g were randomly distributed into fifteen of 300 L circular flow-through tanks (fifteen fish per tank). Five treatments with different days of feeding a week were prepared in triplicate: fish were hand-fed with EP to apparent satiation once a day, seven days a week (7DF), which was used as the control group or consecutive six, five, four and three days a week, for 12 weeks, referred to as 6DF, 5DF, 4DF and 3DF treatments, respectively. Weight gains and specific growth rates of fish in 6DF treatment were higher than those of fish in 7DF, 4DF and 3DF treatments, but not different from those of fish in 5DF treatment. Daily feed intake of fish in 6DF and 7DF treatments was higher than that of fish in 5DF, 4DF and 3DF treatments. Feed efficiency and protein efficiency ratio of fish were not different among treatments. There was no difference in the chemical composition of fish between treatments. Results of this study demonstrated that feeding five days per week could be recommended for subadult olive flounder fed extruded pellet in suboptimal temperature.

Effect of Dietary Protein and Lipid Levels on Compensatory Growth of Juvenile Olive Flounder (Paralichthys olivaceus) Reared in Suboptimal Temperature

Effect of dietary protein and lipid levels on compensatory growth of juvenile olive flounder (Paralichthys olivaceus) was determined in suboptimal temperature (). Five hundred forty fish averaging 79.2 g were randomly distributed into 27 of 300 L flow-through tanks (20 fish/tank). Nine treatments were prepared in triplicate: fish were hand-fed with control (C) diet for 10 weeks (10WF-C); four fish groups were starved for 1 week and then fed with C, high protein (HP), high lipid (HL) and combined high protein and high lipid (HPL) diets for 9 weeks, referred to as 9WF-C, 9WF-HP, 9WF-HL, 9WF-HPL, respectively; and other four fish groups were starved for 2 weeks and then fed with C, HP, HL and HPL diets for 8 weeks, referred to as 8WF-C, 8WF-HP, 8WF-HL and 8WF-HPL, respectively. Weight gain and specific growth rate of fish in 9WF-HP, 9WF-HPL, 8WF-HP and 8WF-HPL treatments were higher than those of fish in 9WF-HL and 8WF-HL treatments. Feed efficiency of fish in 8WF-HP treatment was higher than that of fish in 9WF-C, 9WF-HL and 8WF-HL treatments. Protein efficiency ratio of fish in 10WF-C, 8WF-C, 8WF-HP and 8WF-HPL treatments was higher that that of fish in 9WF-HL and 8WF-HL treatments. Juvenile olive flounder subjected to 2-week feed deprivation could achieve full compensatory growth with dietary supplementation of protein or combined high protein and high lipid.

Effects of Dietary Inclusion of Red Ginseng Byproduct on Growth, Body Composition, Serum Chemistry, and Lysozyme Activity in Juvenile Olive Flounder (Paralichthys olivaceus)

This study examined the effects of the dietary inclusion of various concentrations of red ginseng byproduct (RB) and a mixture containing red ginseng byproduct, garlic extract, yeast and filler (CR) on the growth, body composition, serum chemistry, and lysozyme activity of juvenile olive flounder (Paralichthys olivaceus). Juvenile fish (n= 630) weighing 5.0 g were randomly distributed into 21 180 L flow-through tanks (30 fish/tank). Seven experimental diets were prepared in triplicate: a control diet without additive, and diets containing 0.5, 1 and 2% concentrations of RB (RB-0.5, RB-1, RB-2) and CR (CR-0.5, CR-1, CR-2) at the expense of wheat flour. After an 8-week feeding trial, serum chemistry and lysozyme activity of fish were measured. Mean weight gain was significantly higher in fish fed the control diet than in fish fed the RB and CR diets. The dietary inclusion of RB and CR reduced feed utilization. Mean serum glucose and triglyceride (TG) levels were higher in fish fed the control diet than in fish fed the other diets. Mean glutamate pyruvate transaminase (GPT) levels of fish fed the control and RB-2 diets were higher than those of fish fed the RB-0.5, RB-1, CR-1, and CR-2 diets. Mean lysozyme activity levels of fish fed the RB-0.5 and RB-1 diets were higher than those of fish fed the control and CR diets. The results of this study indicate that red ginseng byproduct may be utilized as an immunostimulant rather than as a growth promoter for juvenile olive flounder. Dietary inclusion of 0.5% red ginseng byproduct effectively improved serum glucose, GPT, TG, and lysozyme activity of the fish in this study.

Effects of Dietary Nutrient Composition on Compensatory Growth of Grower Olive Flounder Paralichthys olivaceus under Different Feeding Regimes at Suboptimal Temperature

The effects of dietary nutrient composition on compensatory growth of grower olive flounder (Paralichthys olivaceus) under different feeding regimes at suboptimal temperature were determined. Four hundred five fish weighing 271.2 g were distributed into 27 300 L flow-through tanks (15 fish per tank). Nine treatments were prepared in triplicate: fish were hand-fed with control (C) diet for 12 weeks (12WF-C); four groups of fish were starved for 1 week and then fed C, high-protein (HP), high-lipid (HL), or combined high-protein and high-lipid (HPL) diets for 11 weeks; these groups are referred to as 11WF-C, 11WF-HP, 11WF-HL, and 11WF-HPL, respectively. Four other groups of fish were starved for 2 weeks and then fed C, HP, HL, and HPL diets for 10 weeks; these groups are referred to as 10WF-C, 10WF-HP, 10WF-HL, and 10WF-HPL, respectively. Weight gain and specific growth rate of fish from 12WF-C group were greater than those of fish from 11WF-C, 11WF-HP, 11WF-HL, 10WF-C, 10WFHP, and 10WF-HL groups, but not different from those of fish from 11WF-HPL and 10WF-HPL groups. Feed-efficiency ratio of fish from 12WF-C, 11WF-HP, 11WF-HPL, 10WF-HL, and 10WF-HPL groups was higher than that of fish in 11WF-C, 11WF-HL, 10WF-C, and 10WF-HP groups. The results of this study demonstrated that grower olive flounder subjected to 1- or 2-week feed deprivation were able to achieve full compensatory growth at suboptimal temperature only when fed HPL diet.

선발 육종넙치 Paralichthys olivaceus 및 일반넙치의 성장비교

To estimate the effect of selective breeding on the improvement of growth in olive flounder Paralichthys olivaceus, we compared the growth of a strain selected for rapid growth to that of an unselected strain from a commercial hatchery. The fish strains were fed with either moist pellets (MP) (dry matter, 59.8% crude protein; 14.1% lipid) or extruded pellets (EP) (dry matter, 50.4% crude protein; 13.8% lipid) for 190 days and were reared under similar conditions. The mortality rates were less than 2% and were not significantly different among the experimental groups. The growth rate of the selected fish was significantly greater than that of the unselected fish regardless of the diet type, and both strains fed MP grew significantly faster than those fed EP. The selected fish consumed more feed than the unselected fish. However, there was no significant difference in the feed efficiency between the selected and unselected fish. These results demonstrate that the selected fish exhibited superior growth rates, and that this was associated with a greater intake of food. Thus, selective breeding may be useful for improving the growth of commercial olive flounder.

Effect of dietary nutrient composition on compensatory growth of juvenile olive flounder Paralichthys olivaceus using different feeding regimes

Effect of dietary nutrient composition on compensatory growth of juvenile olive flounder, Paralichthys olivaceus using different feeding regimes was determined. Six treatments were prepared in triplicate: fish were daily hand-fed with the control (C) diet twice a day, 7 days a week, for 8 weeks (8WF-C); fish were starved for 1 week, and then fed with the C and high protein and lipid (HPL) diets twice a day, 7 days a week, for 7 weeks, referred to as 7WF-C and 7WF-HPL, respectively; and fish were starved for 2 weeks, and then fed with the C, HPL and HPL with supplementation of the mixture of amino acids (HPLA) diets twice a day, 7 days a week, for 6 weeks, referred to as 6WF-C, 6WF-HPL and 6WF-HPLA, respectively. Growth of fish in 7WF-HPL treatment was greater than that of fish in any other treatments. Feed efficiency of fish in 7WF-HPL, 6WF-HPL and 6WF-HPLA treatments was higher than that of fish in 8WF-C, 7WF-C and 6WF-C treatments. The high protein and lipid diet effectively improved compensatory growth of fish. However, supplementation of the mixture of amino acids into the high protein and lipid diet did not improve compensatory growth of fish further.

Effects of dissolved oxygen concentration and stocking density on the growth, energy budget and body composition of juvenile Japanese flounder, Paralichthys olivaceus (Temminck et Schlegel)

An energetic method was used to investigate the effects of stocking density and dissolved oxygen (DO) concentration on the growth of juvenile Paralichthys olivaceus. Fish, with initial weights of 14±2.1 g, were exposed to a normal and a high DO of 5.5±0.5 and 14±2 mg L−1, as well as four stocking densities per DO concentration (100, 200, 300 and 400 ind m−2 for the normal DO and 200, 400, 600 and 800 ind m−2 for the high DO). The feed efficiency (FEW) decreased significantly with increasing stocking density and increased significantly with increasing DO concentration. The maximum weight was achieved at 400 ind m−2 under a high DO depending on our rearing conditions. The stocking density and DO concentration change energy ingestion and its allocation for respiration, growth and excretion lost in nitrogen excretion, but do not affect the energy loss through faeces. The results of the body composition of fish indicated that the stocking density and DO concentration had no significant effects on the moisture, lipid content and gross energy, but are affected by the same. Energetic analysis demonstrated that high DO concentrations could alleviate the growth depression caused by high stocking densities, decrease energy loss in respiration and nitrogen excretion and increase the energy proportion allocated to growth.

Effect of dietary nutrient composition on the growth of olive flounder (Paralichthys olivaceus) with different feeding regimes

We have examined the effect of dietary nutrient composition on the growth, body composition and blood chemistry of juvenile olive flounder (Paralichthys olivaceus) maintained on two different feeding regimes. Three experimental diets [HP (high protein), HE (high energy) and IPE (intermediate protein and energy)] were crossed in a two-factor design with the two feeding regimes, which consisted of 2WS + 2WF (2-week starvation and then 2-week feeding) and 4WS + 4WF (4-week starvation and then 4-week feeding)], for 8 weeks. The total days of feeding in all treatments were the same. The final weight of fish was affected by feeding regime, but not by dietary nutrient composition. Long-term starving and feeding (the 4WS + 4WF treatments) yielded higher growth than the alternating short-term starving and feeding regime (2WS + 2WF treatments). The feed consumption of fish was affected by dietary nutrient composition, but not by feeding regime, while the feed efficiency of fish was affected by feeding regime, but not by dietary nutrient composition. Moisture, crude protein and crude lipid contents of the liver of the fish were affected by dietary nutrient composition, but not by feeding regime.

Effects of feeding frequency and feed type on the growth, feed utilization and body composition of juvenile olive flounder, Paralichthys olivaceus

A factorial (3 × 4) feeding trial was conducted to investigate the effects of feeding frequency and feed type on the growth performance, feed utilization and body proximate composition of juvenile olive flounder. Three feed types including a sinking moist pellet (MP), a sinking dry pellet (DP) and a floating extruded pellet (EP) were used. Fish (average weight, 11.1 ± 0.4 g) were randomly distributed in thirty-six 300 L tanks in a flowthrough system. Triplicate groups (30 fish per tank) of fish were fed each feed type to visual satiation at three meals per day, two meals per day, one meal per day and one meal every 2 days for 7 weeks. At the end of the feeding trial, the survival of fish was not significantly different among the treatments. Weight gain was affected by the feeding frequency. The highest weight gain was observed in fish fed the EP at three meals per day. The daily feed intake of fish fed the MP and DP tended to be higher than that of fish fed the EP at each feeding frequency. The feed efficiency and the protein efficiency ratio of fish fed the EP were higher than those of fish fed the MP and DP. The body proximate composition of fish was altered by the feeding frequency. The crude lipid content increased with the increase in the feeding frequency. The present findings suggest that three feedings per day at visual satiation of the floating EP may be sufficient for the maximal growth performance of olive flounder grown from 11 to 60 g.

배합사료 공급율 및 공급횟수가 겨울철에 사육된 육성기 넙치의 성장 및 체조성에 미치는 영향

Two 15-week feeding trials were conducted to investigate how the rate and frequency of feeding affected the winter growth of olive flounder (<TEX>$13^{\circ}C$</TEX>). In the first experiment, triplicate groups of fish (initial mean weight <TEX>$117{\pm}6.0$</TEX> g) were fed extruded pellets twice a day at feeding rates of 0.1, 0.25, 0.4, 0.55, and 0.57% (satiation) body weight per day (BW/d). The weight gain, specific growth rate, and feed efficiency increased significantly (P<0.05) with the feeding rates from 0.1 to 0.55% BW/d, but no significant differences in these parameters were found for fish fed diets of 0.55% BW/d and satiation. The moisture and ash contents of whole body of fish tended to decrease as the feeding rate increased, but the opposite trend was found for crude lipid content. In the second experiment, triplicate groups of fish (initial mean weight <TEX>$117{\pm}6.3$</TEX> g) were fed extruded pellets to apparent satiation at the three different feeding frequencies: one meal 2 days, one meal a day and two meals a day. The weight gain and specific growth rate of fish fed one meal 2 days were significantly (P<0.05) lower than those of fish fed one or two meals a day, whereas no significant differences in the weight gain and specific growth rate were found between fish fed one and those fed two meals a day. Feed efficiency and condition factor were not significantly affected by feeding frequency. Based on these results, a feeding rate of 0.3% BW/d is recommended as maintenance feeding level, and the optimum feeding frequency is one meal a day with satiation feeding for the growth of olive flounder (117-147 g) during winter (<TEX>$13^{\circ}C$</TEX>).

Effects of Dietary Protein and Lipid Levels on Growth and Body Composition of Subadult Olive Flounder, Paralichthys olivaceus, at a Suboptimal Water Temperature

A 3 × 2 factorial experiment was conducted to investigate the proper dietary protein and lipid levels for growth of subadult olive flounder reared in suboptimal water temperature. Six diets were formulated to contain three levels of protein (40, 45, and 50%) and two levels of lipid (7 and 14%). Triplicate groups of fish (initial body weight of 255 g) were hand‐fed to apparent satiation for 14 wk in suboptimal water temperature (15.5 ± 1.3 C). The highest weight gain and feed efficiency were observed in fish fed the 45 and 50% protein diets with 14% lipid. Protein efficiency ratio, daily feed intake, condition factor, and hepatosomatic index of fish fed the 14% lipid diets were significantly or slightly higher than those fed the 7% lipid diets at the same protein level. Crude lipid contents of the liver and viscera of fish fed the 14% lipid diets were significantly higher than those fed the 7% lipid diets at the same protein level. The results of this study suggest that at 15 C an increase of dietary lipid level from 7 to 14% can improve growth and protein utilization irrespective of protein levels (40, 45, and 50%), and the diet containing 45% protein and 14% lipid would be suitable for optimal growth and effective protein utilization of subadult olive flounder when reared at 15 C.