The transmission potential of Loma salmonae (Microspora) in the rainbow trout, Oncorhynchus mykiss (Walbaum), is dependent upon the method and timing of exposure

The ability of a parasite to transmit from one fish to another is important in the dissemination of disease. Groups of 25 naive rainbow trout (RBT), Oncorhynchus mykiss (Walbaum), were exposed to Loma salmonae by feeding on the viscera (gills, hearts and spleens) from L. salmonae -infected donor RBT (DRBT) or by cohabitation with infected DRBT. Exposure occurred 3, 7, 11 and 15 weeks after the DRBT were infected. All naive RBT were examined 7 weeks post-exposure (PE) to the DRBT. Naive RBT, exposed to DRBT at week 3 PE, by feeding on viscera or by cohabitation, failed to develop visible branchial xenomas. Cohabiting naive RBT with DRBT, at week 7 PE and week 11 PE, resulted in the development of branchial xenomas. Xenomas failed to develop in naive RBT exposed via cohabitation to week 15 PE DRBT. Naive RBT, exposed by feeding on the viscera of DRBT at week 7 PE, week 11 PE and week 15 PE, developed branchial xenomas. The transmission potential of viscera from L. salmonae -infected DRBT at week 15 and week 20 PE was also examined. Naive RBT, fed with viscera free of visible branchial xenomas, from DRBT at week 15 PE and week 20 PE, developed branchial xenomas by week 7 PE. A polymerase chain reaction (PCR) was used to detect L. salmonae DNA from the water and sediments of a tank of L. salmonae -infected RBT at week 7 PE. The method and timing of exposure of naive fish to L. salmonae -infected fish are important in disease transmission and may be useful in predicting and preventing disease outbreaks in aquaculture.     

Interaction of water temperature and challenge model on xenoma development rates for Loma salmonae (Microspora) in rainbow trout, Oncorhynchus mykiss (Walbaum)

This study evaluated the regulatory effects of water temperature on the development of branchial xenomas caused by Loma salmonae using a high-dose per os-challenge model compared with a low-dose cohabitation-challenge model. Approximately 275 juvenile rainbow trout (RBT), Oncorhynchus mykiss, were randomly distributed to six tanks with two tanks each maintained at 11, 15 and 19 degrees C. Fish in one tank from each temperature setting were exposed per os to macerated L. salmonae-infected gill material and fish in the other tank from each temperature setting were exposed to L. salmonae using the cohabitation-challenge model. Fish were monitored for the development of branchial xenomas beginning at day 21 post-exposure. Survival analyses were used to evaluate the effect of water temperature and challenge model on the number of days until the first visible branchial xenoma was detected. The survivor curves for the per os-challenge model revealed that there was at least one significant difference, whereas the cohabitation challenge did not reveal any significant differences amongst the temperature settings. The proportional hazards model revealed a significant interaction between the challenge model used and water temperature. This indicated that the effect of water temperature was different depending on challenge model. Additionally, from the mean xenoma intensities, on average, the per os-challenged fish showed higher xenoma intensity compared with the cohabitation-challenged fish. Overall, the impact of water temperature on disease pathogenesis was greater when the RBT were per os challenged compared with using the cohabitation model.     

Loma salmonae-associated xenoma onset and clearance in rainbow trout, Oncorhynchus mykiss (Walbaum): comparisons of per os and cohabitation exposure using survival analysis

Survival analysis techniques were used to compare experimental exposure methods of Loma salmonae (Microspora) in rainbow trout (RBT) by measuring xenoma onset and clearance time. Twenty‐eight naive RBT were exposed per os (fed L. salmonae spores) and 28 RBT were exposed by cohabitation with 28 L. salmonae‐infected RBT. Exposed fish were examined once every week (7 days) post exposure (PE). For xenoma onset, the median survival time, the time to first appearance of branchial xenomas, was 6 weeks PE for both per os and cohabitation exposure. For xenoma clearance, the median survival time, the time to total clearance of branchial xenomas, was 10 weeks for per os exposure and 12 weeks for cohabitation exposure. There was a significant difference between the survival curves of per os fish compared with cohabited fish for both xenoma onset and xenoma clearance. The incidence rate of xenoma development was greater for per os exposure (0.1745 cases per fish‐week) compared with cohabitation exposure (0.1342 cases per fish‐week). Similarly, the rate of xenoma clearance was greater for per os exposure (0.1028 cases per fish‐week) compared with cohabitation exposure (0.0885 cases per fish‐week). Differences between exposure methods were attributed to differences in the frequency and duration of exposure to spores. Survival analysis was useful for examining the onset and clearance of L. salmonae and may have applications for understanding disease dynamics in aquaculture.     

Whole body net ion fluxes, plasma electrolyte concentrations and haematology during a Loma salmonae infection in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

Loma salmonae infections of salmonids culminate in the development of branchial xenomas and subsequent focal hyperplasia of the lamellar or filament epithelium following xenoma rupture and spore release. The effects of this acute branchial disruption upon net ionic flux rates and plasma electrolyte concentrations were determined in juvenile rainbow trout given an experimental oral exposure to L. salmonae. Mean numbers of branchial xenomas peaked at week 5 post-exposure (PE), which coincided with a reduction in the specific growth rate, although there were no significant differences in mass, length or condition of Loma-exposed fish compared with unexposed controls. Following exposure, negative net whole body Na(+) and K(+) fluxes decreased, whereas net Cl(-) fluxes remained unchanged compared with non-exposed control fish. At week 3 PE during the initial branchial xenoma formation stage, there was a significant negative whole body net K(+) flux in Loma-exposed trout compared with other points during the exposure and subsequent infection. Additionally, Loma-exposed fish had marginally elevated plasma Na(+) and Cl(-) concentrations, whilst K(+) levels remained unchanged, compared with control fish. Although there was a progressive decrease in leucocrit, haematocrit remained unchanged over the course of the Loma exposure and subsequent infection. These results suggest that ionic compensation can occur at the gills during the development of xenomas during exposure to L. salmonae and the resultant infection, therefore allowing defence of plasma electrolyte concentrations, unlike the acute ionic disturbances seen with some other parasitic diseases.     

分级对银鲫生长和个体大小差异的影响

在室内水槽进行12周的饲养实验以检验分级对银鲫生长和鱼群内个体大小差异的影响。用隔网将实验水槽分为两部分,每个水槽内放养10尾大鱼（体重8.0~9.0 g）和10尾小鱼（体重6.5~7.5 g）,分级时将个体大小相近的10尾鱼分布在隔网同一侧。实验中,3组鱼分别隔1周、2周或4周分级1次,1组鱼不进行分级作为对照。鱼摄食率和生长率随分级间隔时间缩短而降低。实验结束时,隔1周分级1次的鱼体重低于对照组,隔4周分级1次的鱼体重与对照组无显著差异。实验结束时被分级的鱼群中大鱼体重的变异系数高于小鱼,表明大鱼对分级操作更敏感。本实验结果表明,分级未能明显提高银鲫生长速度和降低鱼群内个体大小的差异程度。     

The effects of grading on the growth and survival of juvenile Dover sole (Solea solea L.)

A 3-month study was carried out to investigate the effects of grading on the overall production, growth performance and survival of juvenile Dover sole (Solea solea L.). Juvenile fish (4.0–40.4 g) were sorted into three size groups: small (4.0–15.5 g), medium (16.0–21.5 g) and large (22.0–40.5 g). In addition, a group of unsorted fish was followed for comparison. The fish from each sorted group and the unsorted group were divided between triplicate tanks at a stocking density of 1.5 kg m⁻². The fish were weighed and counted 21, 42, 63 and 92 days after stocking. In addition, 30 randomly chosen fish in each tank (=90 from each group) were individually tagged. The survival, size distribution, growth and productivity were calculated for small, medium, large and unsorted groups. In addition, comparisons were made between combined sorted and unsorted fish. There was no significant difference between the mean weight and distribution of sorted and unsorted fish by the end of the trial. An increased overall productivity in combined sorted fish was observed. Regular grading could therefore still be beneficial for sole farming as long as the grading interval supports maximum growth (in this case over 90 days). Survival was not significantly affected by the grading process.     

Altered tissue distribution of Loma salmonae: effects of natural and acquired resistance

This study compared and contrasted the fate of the microsporidian Loma salmonae , a branchial pathogen of salmonids of the genus Oncorhynchus , upon exposure of (1) naive susceptible rainbow trout (RT) O. mykiss , (2) naive RT passively immunized with sera from RT previously exposed to L. salmonae , (3) previously exposed and resistant RT and (4) two species believed to be innately resistant to the parasite, Atlantic salmon (AS) Salmo salar and brook trout (BT) Salvelinus fontinalis . The fish were infected per os with viable L. salmonae spores. The infection was followed in the fish by detection of parasite DNA by polymerase chain reaction (PCR) at several times post-infection. Spore germination and intestinal invasion by the parasite occurred in all groups of fish. In the susceptible RT, parasite DNA was detected in the heart by day 3 post-exposure (PE), followed by the gill at 2 weeks PE, whereas visible xenoparasitic complexes (xenomas) were detected by week 4 PE. In the passively immunized RT, the parasite's fate was similar to that of controls, however, its arrival in the heart was delayed by 1 week. A delay was also detected in RT which had been previously exposed to L. salmonae and then recovered from disease. In these resistant fish, the parasite was able to reach the heart by week 3 PE, however, it failed to reach the gill and form xenomas. In AS and BT, the parasite reached the heart and gills quickly, where it remained for 2 weeks before being cleared; xenomas never formed. We speculate that failure to complete the life cycle in AS, BT and resistant fish might be because of interference by the immune system in the development of the parasite, resulting in the absence of disease in these fish.     

Effect of Continuous Food Supply on the Oxygen Consumption of Young Mediterranean Yellowtail (Seriola dumerili Risso, 1810)

The aim of this work was to investigate the effect of a continuous food supply on the oxygen consumption of young Mediterranean yellowtails (Seriola dumerili Risso, 1810) during the photophase period (14LL:10DD). Four groups with six fish each, weighing individually approx. 600 g, were distributed into open 2 m³ quadrangular fibreglass tanks, and fed with commercial pellets for 60 days. Two of the tanks received a continuous feed supply by means of automatic band feeders (ABF), whilst fish in the other two tanks were fed by hand, twice a day. To improve accuracy in calculating oxygen consumption, the effect of oxygen diffusion between the air and the water was determined by the use of a control tank of similar characteristics, containing no fish. Oxygen consumption instantaneous rate was calculated by the difference between dissolved oxygen concentrations in tanks with and without fish, multiplied by the water flow and divided by the estimated total fish biomass in each tank. In both feeding regimes, an increase in the oxygen consumption levels after feeding commencement was observed. The amplitude, however, was lower and the duration of feeding effect was higher in the group fed by ABF.     

Influence of management protocols on carp growth under nursery conditions: relative importance of food and water quality

Twenty outdoor holding tanks (10 m–3 each), were filled with ground water and grouped into five feeding schemes: live zooplankton cultured outside the fish growing tank (LFS); direct nursery pond fertilization schedule in static (MS) as well as in exchanged water (EMS); intermediate conditions between the LFS and MS (IS); and supplementary food system using mixture (1:1) of finely ground mustard oilcake and boiled rice (SFS). Two hundred common carp (Cyprinus carpio) fry were introduced into each of the twenty outdoor tanks maintained at ambient temperature outside the laboratory. After 90 days of rearing, the fish were harvested and analysed for various growth parameters and food conversion efficiency. The average weight of carp attained in the LFS was significantly higher than that in the other four feeding schemes. The frequency distribution of final body weight of common carp showed the preponderance of large and small fish in the LFS and MS, respectively. Likewise, plankton intake by the carp fry was highest in the LFS. The rate of survival was much higher in the LFS as compared with the rest of the treatments. The water quality remained far better in the former than the latter. © Rapid Science Ltd. 1998     

Influence of stocking density on growth of juvenile red porgy Pagrus pagrus L. under different feeding conditions

The influence of stocking density and feeding regime on the growth of red porgy was studied during winter and spring 1997. Fish were held in 500-L tanks at densities of either 50 or 100 fish per tank, and were fed by means of self-feeders under 6 h restricted (day or night) or free-access feeding regimes. Fish were tagged individually, and weight gain was recorded by individual weighing every second week over an 8-week period during each season. In winter, growth was influenced by feeding time. Fish tended to grow best when fed without restriction and worst when fed at night, although differences were not significant when tank means were compared. Stocking density was influential in the spring trial. Fish stocked at low density and feeding freely grew better than high-density fish that fed either freely or at night. The division of fish into three size classes revealed that, within each treatment, no differences occurred among classes, but growth of fish belonging to the same class was influenced by rearing conditions. No significant differences were found among feeding regimes in terms of the coefficients of weight variation ratio (CV_f:CV_i) and feed efficiency.     

Effects of Gender and Size on Feed Acquisition in the Pacific White Shrimp Litopenaeus vannamei

Pacific white shrimp, Litopenaeus vannamei, are sexually dimorphic for growth, where subadult and adult females typically are larger than males of the same age. This character may be attributed to physiological and/or behavioral differences between the sexes. To determine if growth differences are the result of a more aggressive feeding behavior by females, four concurrent feeding trials were conducted to study the effects of gender and size on feed acquisition time. Feeding trials consisted of tanks (three replicate tanks per trial) stocked with (1) all females with small‐ and large‐size groups, (2) all males with small‐ and large‐size groups, (3) a random selection of males and females (resulting in larger females than males), and (4) males and females of equal size. Depending on the trial, tanks were stocked with either an equal number of males and females or small and large shrimp. Shrimp were fed a limited ration of squid, and the total feeding time (TFT) of shrimp between groups within a tank was compared. Results show that both gender and size are important factors in TFT as large shrimp out‐competed small shrimp in both all‐female and all‐male feeding trials. Gender is more important than size as males out‐competed females for feed even when they were smaller than competing females. These results suggest that sexual growth dimorphism is not the result of more aggressive feeding by females. In fact, males have a competitive advantage over females in acquiring feed. These results are counterintuitive because females typically are larger than males. Additional research is needed to investigate the physiological basis for sexual growth dimorphism in this commercially important shrimp.     

A study of the bacterial types occurring on the skin and in the intestines of farmed plaice (Pleuronectes platessa L.)

Four small identical tanks fed with power station effluent were each stocked with 10 × “1-group” plaice. The fish in each of the tanks were fed minced fish containing different binding agents. Bacteria were isolated from skin and intestinal samples of two fish taken from each tank. Five generic/group generic types were isolated from fish skin while ten types were isolated from fish intestines. Organisms belonging to the Enterobacteriaceae were isolated from both skin and intestines. The types isolated from intestines also included Aeromonas species (spp.). However, strict anaerobes were unable to be isolated.All intestinal bacteria were tested for their ability to grow on a minimal salt agar medium containing each of the binders as sole carbon source. There was no special relationship between the binder to which the isolates were exposed in the fish intestine and the binders which they could utilise as sole carbon sources. Few isolates could utilise hydroxypropyl-methyl cellulose.     

Dietary yeast culture supplementation improves initial rearing of McConaughy strain rainbow trout

The addition of a yeast culture food supplement (DVAqua from Diamond V. Mills, Cedar Rapids, IA, USA) was evaluated during feeding of McConaughy strain rainbow trout Oncorhynchus mykiss. Two trials were run consecutively, starting with initial feeding, and were replicated over 2 years. The yeast culture was added to commercial trout starter at levels of 0.125 and 0.25 g kg^?1. The number of rainbow trout that died during the first 4 weeks of rearing was significantly reduced in the tanks receiving either of the yeast culture‐supplemented diets compared with the tanks receiving a control starter diet. Ending tank weights and gain were significantly and consistently greater in the tanks fed the 0.25 g kg^?1 yeast culture diet. Individual fish weights were also significantly heavier in the fish‐fed yeast culture containing diets in each year of the study at the end of 27 days. In the trials from 4 to 8 weeks postinitial feeding, mortality rates were significantly less only in the tanks receiving 0.25 g kg^?1 yeast culture supplementation. Individual fish lengths and weights at the end of the second trial were significantly greater in the tanks receiving either level of yeast culture compared with the control diet only in 1 year. Total tank weights and feed conversion were not significantly different between any of the treatments. The inclusion of DVAqua yeast culture provided significant increases in trout survival and growth through the first 4 weeks of feeding, with continued benefits for the next 4 weeks.     

Normal and aberrant tissue distribution of Loma salmonae (Microspora) within rainbow trout, Oncorhynchus mykiss (Walbaum), following experimental infection at water temperatures within and outside of the xenoma-expression temperature boundaries

Temperatures above 20 °C or below 9 °C interrupt the life cycle of the gill intracellular microsporidian parasite Loma salmonae (Microspora) prior to sporogony, inhibiting the production of xenomas. This study intended to characterize this life-cycle failure. Juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), were experimentally infected with L. salmonae spores, and the effect of water temperature on the progress of infection, as determined by polymerase chain reaction, was compared for fish held at water temperatures of 5, 15 and 21 °C. At 15 °C, parasite DNA was first detected in the heart (3 days post-exposure [PE]), and then in the gills and spleen (2 weeks PE). Branchial xenomas developed by week 4 PE. In contrast, at 5 °C, the arrival of the parasite in the heart was delayed until 7 days PE. However, even though parasite DNA was detected in the gills at 7 days PE, xenomas failed to form in the gill, and by week 4 PE, parasite DNA was no longer detected. In fish held at 21 °C, parasite DNA was detected in the heart, gills and spleen by 3 days post-infection, and similar results were observed at 7 days PE. Xenomas also failed to form in these fish and parasite DNA was no longer detected by week 2 PE. Within the range of temperatures tested in this study, spore germination and delivery of their DNA into the host through the intestinal wall was not blocked by temperature. At 5 or 21 °C, migration to the heart and gills occurred, but at aberrant periods of time. The normal life cycle of L. salmonae may depend on the completion of relatively lengthy, but yet unknown, stages of development within the heart, prior to reaching the gill. This development may be adversely affected by temperature, and explain the temperature limits of this parasite.     

Development of new self-feeding system for mass rearing of ayu <Emphasis Type="Italic">Plecoglossus altivelis altivelis</Emphasis> under artificial and natural light-dark cycles

Self-feeding of grouped ayu Plecoglossus altivelis altivelis was examined under an artificial light-dark (LD) cycle and natural day length using a trigger with a photosensitive sensor. In Experiment 1, approximately 15 juvenile fish (mean body weight, 0.6 g) were kept in 60-L glass tanks (four tanks) under LD 12∶12 (lighting period 06∶00–18∶00 hours) and self-feeding and locomotor activities were simultaneously recorded. Self-feeding was detected within one day and feeding activities were strongly synchronized to the LD cycle, with almost strictly diurnal feeding (98.2%). Although locomotor activities in the upper part of the tank were also greatest during the light phase (76.8%), the activity profiles were different from those of self-feeding, suggesting the validity of the photosensitive sensor. In Experiment 2,25 fish (mean body weight, 15 g) were kept in outdoor 1000-L tanks (four tanks) under natural day length and water temperatures in May, and self-feeding was recorded from mid-August. Stable self-feeding was observed from early September in all the tanks. Nearly all food demands were diurnal, and usually crepuscular. Somatic growth was seen in all tanks. These results demonstrate that the self-feeding system using a photosensitive sensor is applicable for grouped juvenile ayu as small as 0.6 g and adult fish reared under natural conditions.     

Water velocity in commercial RAS culture tanks for Atlantic salmon smolt production

An optimal flow domain in culture tanks is vital for fish growth and welfare. This paper presents empirical data on rotational velocity and water quality in circular and octagonal tanks at two large commercial smolt production sites, with an approximate production rate of 1000 and 1300 ton smolt/yr, respectively. When fish were present, fish density in the two circular tanks under study at Site 1 were 35 and 48 kg/m³, and that in four octagonal tanks at Site 2 were 54, 74, 58 and 64 kg/m³, respectively. The objective of the study was twofold. First, the effect of biomass on the velocity distribution was examined, which was accomplished by repeating the measurements in empty tanks under same flow conditions. Second, the effect of operating conditions on the water quality was studied by collecting and analysing the water samples at the tank’s inlet and outlet. All tanks exhibited a relatively uniform water velocity field in the vertical water column at each radial location sampled. When fish were present, maximum (40 cm/s) and minimum (25–26 cm/s) water rotational velocities were quite similar in all tanks sampled, and close to optimum swimming speeds, recommended for Atlantic salmon-smolt, i.e., 1–1.5 body lengths per second. The fish were found to decrease water velocity by 25% compared to the tank operated without fish. Flow pattern was largely affected by the presence of fish, compared to the empty tanks. Inference reveals that the fish swimming in the tanks is a major source of turbulence, and nonlinearity. Facility operators and culture tank designers were able to optimize flow inlet conditions to achieve appropriate tank rotational velocities despite a wide range of culture tank sizes, HRT’s, and outlet structure locations. In addition, the dissolved oxygen profile was also collected along the diametrical plane through the octagonal tank’s centre, which exhibits a close correlation between the velocity and oxygen measurements. All tanks were operated under rather intensive conditions with an oxygen demand across the tank (inlet minus outlet) of 7.4–10.4 mg/L. Estimates of the oxygen respiration rate in the tank appears to double as the TSS concentration measured in the tank increases from 3.0 mg/L (0.3 kg O₂/kg feed) up to 10–12 mg/L (0.7 kg O₂/kg feed). Improving suspended solids control in such systems may thus dramatically reduce the oxygen consumption and CO₂ production.     

Induced resistance in rainbow trout, Oncorhynchus mykiss (Walbaum), to gill disease associated with the microsporidian gill parasite Loma salmonae

Branchial xenomas were detected by week 5 and disappeared by week 10 after naive juvenile rainbow trout, held at 14.5 °C, were fed or intubated with Loma salmonae ‐infected gill tissue preparations. Upon re‐challenge with L. salmonae , these fish were protected from disease and branchial xenomas did not develop. Branchial xenomas were never detected in naive fish held at 10 °C and exposed to L. salmonae . When these fish were re‐challenged with L. salmonae at 14.5 °C, they were also protected from the disease. Branchial xenomas also developed after naive fish, held at 14.5 °C, were injected intraperitoneally with a semipurified preparation of fresh spores, but generally did not develop after intraperitoneal injection with a preparation of spores subjected to freezing and thawing before use. Fish that had received fresh spores intraperitoneally were completely resistant to disease when re‐challenged via oral delivery of spores, whereas those that had received frozen spores were incompletely, but significantly, protected from disease compared with naive fish. We conclude that infection with L. salmonae induces strong protection towards the disease upon re‐exposure to spores, and that the protection does not depend on the completion of the parasite's life cycle, thus establishing the basis for further research on vaccine development for this disease.     

Energy partitioning in cultured juvenile Pacific bluefin tuna,Thunnus orientalis (Temminck & Schlegel, 1844)

The characteristics of dietary utilization, energy conversion efficiency, metabolic rate and energy partitioning were measured for cultured Pacific bluefin tuna (PBT) juveniles fed on an artificial diet. Thirty‐one juveniles (1.1 ± 0.3 g BW) were stocked into each of two 2500 L tanks to measure oxygen consumption (?O₂), swimming speed, digestibility and growth performance. ?O₂ elevated until 2.5 ± 0.3 times of pre‐feeding level within 1.5 h after feeding, except for the first feeding, and returned to pre‐feeding level within 3 h. Swimming speed fluctuation was corresponded with the ?O₂ fluctuation, and both parameters were stable from 02:00 to 06:00 and also during the whole day for starved fish. These indicate that feeding has strong influence on their metabolic rate. Energy partitioning for faecal, urinary and branchial, heat increment and voluntary activity, standard metabolism, and retained energy were calculated to be 17.2%, 5.9%, 14.9%, 41.3% and 20.7% of total ingested energy, respectively. The results indicate that, unlike other fish, juvenile PBT distribute large amount of energy for maintenance, which allows only a little proportion of ingested energy available for growth.     

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.