Effects of protein and lipid sources on the growth and survival of red sea bream Pagrus major and Japanese flounder Paralichthys olivaceus receiving micro-bound diets during larval and early juvenile stage

The effects of dietary protein and lipid sources on growth and survival of the red sea bream Pagrus major (30‐days old) and Japanese flounder Paralichthys olivaceus (15‐days old) were examined using four zein‐microbound diets (MBD) containing the following nitrogen and lipid sources: MBD‐1, SBP‐1000 (soybean peptides with molecular weights of about 1000) + fish oil calcium soap (FOCS); MBD‐2, SBP‐3000 (molecular weights of about 3000) + FOCS; MBD‐3, soybean protein isolate (SPI) + FOCS; MBD‐4, SBP‐1000 + stearoyl calcium lactate (SCL). Six groups of the test fish were maintained on the following diets for 30 days; group 1, live food; group 2, 1/2 live food + 1/2 MBD‐1; group 3, MBD‐1; group 4, MBD‐2; group 5, MBD‐3; group 6, MBD‐4. In the red sea bream, high performance in terms of total length (TL) and body weight gain (BWG) was obtained in groups 1, 2, 3 and 4. However, the fish receiving MBD‐3 (group 5) and MBD‐4 (group 6) had shorter TL and lower BWG than those receiving the other diets. Regarding the Japanese flounder, high performance in terms of TL, BWG, and survival rate (SR) was obtained in groups 1 and 2. Group 3 receiving MBD‐1 gave the BWG and SR close to those of group 2 but lower than group 1. In contrast, groups 5 and 6 receiving MBD‐3 or MBD‐4 alone had significantly (P < 0.05) shorter TL and lower BWG than groups 1 and 2. The present study thus indicated that soybean peptides with molecular weights of 1000–3000 and FOCS are superior to SPI and SCL as nitrogen and lipid sources of MBD for the red sea bream and Japanese flounder at larval and early juvenile stage.     

Effects of Fish Size and Water Temperature on the Acute Toxicity of Copper for Japanese Flounder,Paralichthys olivaceus,and Red Sea Bream,Pagrus major

The acute toxicities of copper were examined for Japanese flounder, Paralichthys olivaceus, and red sea bream, Pagrus major, in terms of fish size and water temperature. Artificial seawater of low pH of 5.4–6.7 was used as testing water to keep dissolved copper concentration at 0.04–41 mg Cu/L. Japanese flounder of 0.3–17 g and red sea bream of 0.5–13 g were exposed to different concentrations of copper for 96 h at 20 C under semistatic condition. Median‐lethal concentration for 96 h of Japanese flounder and red sea bream were 8.7–12.2 and 2.0–5.2 mg Cu/L, respectively. No significant relationships were observed between median‐lethal concentrations for 96 h and fish size for Japanese flounder, while the value decreased significantly with increasing fish size for red sea bream. Effect of water temperature on the acute toxicity was examined for Japanese flounder of 0.3 and 0.4 g at 10, 15, 20, and 25 C and red sea bream of 0.5 and 1.0 g at 12, 15, 20, and 25 C. Ninety‐six‐hour median‐lethal concentrations for Japanese flounder and red sea bream were 5.1–11.2 and 1.0–5.3 mg Cu/L, respectively. No significant relationships were observed between median‐lethal concentrations for 96 h and water temperature for both fish species.     

Effects of fish size and water temperature on the acute toxicity of boron to Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> and red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

ABSTRACT:     The acute toxicities of boron were examined for Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major in terms of fish size and water temperature. Japanese flounder of 0.1–70.0 g and red sea bream of 0.6–20.3 g were exposed to different concentrations of boron for 96 h at 20°C under semi-static conditions. In both fish species, the median lethal concentration (LC₅₀) for 96 h of boron increased linearly with increasing fish size, ranging from 108 to 252 mg B/L for the flounder, and from 97 to 172 mg B/L for the sea bream. The effect of water temperature on acute toxicity was examined for Japanese flounder of 0.6 and 1.5 g at 10, 15, 20 and 25°C, and for red sea bream of 0.6 and 2.4 g at 12, 15, 20 and 25°C. The toxicity of boron for the flounder increased linearly with increasing water temperature. The 96 h LC₅₀ values ranged from 299 to 108 mg B/L for the 0.6 g flounder and from 350 to 113 mg B/L for the 1.5 g flounder. A similar trend was shown for the 2.4 g red sea bream; however, the relationship for the 0.6 g red sea bream was not significant.     

Marine Fish Larvae Feeding: Formulated Diets or Live Prey?

In the rearing of larval marine fish, any diet that reduces dependance on live prey production is of technical and economic interest. Weaning juveniles with a completely developed digestive tract to a conventional diet, (i.e., "late weaning") can be successful in any marine fish species. For example, weaning one-month-old sea bass (20 mg) to the study's reference diet, Sevbar, resulted in over 85% survival (40% from hatching) and 1.25 g fish at day 90 (at 19 C)
In contrast, "early weaning" of larvae to special microdiets during the first month is still difficult. The best way to reduce live prey utilization in sea bass is to wean larvae at about 3–4 mg in size (day 20). If weaning could be accomplished 15 days earlier, Artemia savings could be as high as 80%. However, this introduces risks relative to growth retardation (30% weight loss) and lower juvenile quality, including greater size variability and skeletal abnormalities. Similar results have been obtained with commercial microparticles (Fry Feed Kyowa) and experimental microbound diets (MBD) made from raw materials (alginate MBD) or preferably from freeze-dried protein sources (zein MBD).
Total replacement of live prey is still impossible in marine fish. Sea bass larvae fed formulated diets exclusively from first feeding (0.3 mg larval wet weight), or even from their second week of life onwards, exhibited low survival and poor growth. Better results can be obtained when formulated diets are used in combination with live prey from first feeding, although the optimal ratio of live prey to formulated diet is still to be specified.     

Influence of different dietary amino acid patterns on growth and body composition of juvenile Japanese flounder, Paralichthys olivaceus

A feeding trial using five semi-purified diets (50% crude protein) was conducted to investigate the effects of different dietary amino acid patterns on growth and body composition of juvenile Japanese flounder. The control diet contained casein and gelatin as intact protein sources and four other diets contained 30% casein–gelatin (2:1, w/w) and 20% crystalline amino acids (CAA). CAA were added to the diets to simulate the amino acid pattern found in red sea bream egg protein (REP), Japanese flounder larvae whole body protein (FLP), Japanese flounder juvenile whole body protein (FJP), and brown fish meal protein (BFP), respectively. The test diets were fed to triplicate groups of juveniles (2.75±0.05 g) twice a day for 40 days to evaluate weight gain, survival, feed conversion efficiency (FCE), protein efficiency ratio (PER), and apparent protein utilization (APU). The apparent retention of total dietary amino acids in the whole body and A/E ratios of the whole body were also evaluated. The highest weight gain was observed in fish fed the diet containing the dietary amino acid pattern of BFP followed by fish fed the control, FJP, FLP and the REP diets. Percent survival, FCE, PER and APU were also significantly (P<0.05) affected by the amino acid pattern in the diets, indicating the highest value in fish fed the BFP diet. Except for a few amino acids, the amino acid composition of the whole body did not show marked differences with different dietary amino acid pattern. Results suggest that BFP could be more suitable as a reference amino acid pattern in the diet of juvenile Japanese flounder compared to the amino acid pattern of FLP, FJP or REP.     

Present Status of Research and Production of Japanese Flounder,Paralichthys olivaceus,in Japan

ABSTRACT

Aquaculture of Japanese flounder, Paralichthys olivaceus, started in the middle 1970s in Japan, and the commercial production became extensive in the early 1980s, with development of seedling production and farming techniques. Annual production in 1996 was 7,692 metric tons, ranked fourth among marine cultured finfish after yellow-tail, red sea bream, and coho salmon. Marine finfish aquaculture in Japan is mostly conducted in floating net cages; however, land-based culture tanks are the prevalent culture system for Japanese flounder. The tanks are circular, square, or octagonal and constructed of various materials: concrete, plastic and/or a combination of the two. Culture tanks are generally inside or covered with shade cloths. Sand-filtered sea water is continually supplied to each tank, with 12 to 24 exchanges daily. Three-gram fish are stocked in the culture tank and raised for 1 to 2 years until they grow to 500-1,000 g. Survival ranges from 60 to 80%. Sardines and sand lance, fresh or frozen, are mainly fed; however, use of moist or dry pellets are increasing recently because of the decline in catch of these fishes. Fingerlings are obtained from commercial hatcheries virtually year-round. The fish utilize almost no dietary carbohydrate as an energy source, and an increase of lipid in the diet did not improve the growth, although it did seem to produce a slight increase in protein efficiency ratio. Therefore, diet for Japanese flounder should contain high percentages of protein (fish meal). Finding alternative protein sources for fish meal in the diet has been researched, and the potential of defatted soybean, corn gluten, feather, meat, and meat bone meals have been examined. The optimum temperature for the growth is 20-25°C. Salinity range of 4.4 to 34.0 ppt did not affect the growth of Japanese flounder at 8 g initial body weight.     

Supplementations of dl‐Methionine and Methionine Dipeptide in Diets are Effective for the Development and Growth of Larvae and Juvenile Red Sea Bream,Pagrus major

Growth trials for larvae and juvenile red sea bream, Pagrus major, were conducted to elucidate the efficacy of two molecular forms of methionine; dl ‐methionine (dl ‐Met) and methionine dipeptide (Met‐Met). For the larvae experiment, five experimental diets were formulated and fed to fish (42 mg) for 30 days. A diet which has 15% soy protein isolate served as the control diet. Similarly, test diets supplemented with dl ‐Met and Met‐Met at 0.5%, which were either precoated by zein or intact, were also formulated. For the juvenile experiment, five experimental diets were formulated wherein the control diet contained 25% soy protein isolate. Test diets were supplemented with dl ‐Met and Met‐Met at 0.75%, which were either coated by carboxymethycellulose or intact and fed to juveniles (0.75 g) for 56 days. The results of two feeding trials showed both dl ‐Met and Met‐Met can be equally utilized by red sea bream larvae and juveniles. Coating the amino acid significantly improved both fish larval and juvenile growth performance. The development of digestive protease activity of larvae was significantly influenced by coating the amino acid, but the type of methionine was not a factor in changing the protease activity of larvae.     

Growth performance,survival and body composition of southern flounder Paralichthys lethostigma larvae fed different formulated microdiets

Three experiments were conducted to evaluate the effects of micro‐bound diets (MBD) on southern flounder larvae. In experiment 1, four MBDs were formulated with different protein sources as follows: MBD 1: herring meal, MBD 2: menhaden meal, MBD 3: menhaden and squid meal; MBD 4: menhaden, squid and herring meal. In experiment 2, four MBDs were formulated as follows: MBD 5: menhaden, squid and herring meal; MBD 6: menhaden, squid, herring and attractants; MBD 7: menhaden, squid, herring and casein, and MBD 8: menhaden, squid, herring, casein and attractants. In experiment 3, three groups were maintained as follows: Group 1: live feed; Group 2: co‐fed with MBD 6; and Group 3: MBD 6. In experiment 1 on 35 dph, survival and body weight (BW) of the fish fed MBD 4 was significantly higher than the MBDs 1 and 2. In experiment 2 on 34 dph, fish fed MBD 6 had significantly higher BW than the commercial microdiets. In experiment 3 on 21 dph, fish receiving only MBD had significantly lower survival than the other groups. Growth, survival and larval fatty acid composition suggested that co‐feeding MBD 6, a mixture of marine protein sources plus attractants was more effective than the other MBDs.     

Channel Catfish,Ictalurus punctatus,Immunity to Saprolegnia sp.

ABSTRACT

The Japanese flounder, Paralichthys olivaceus, is one of the most common finfish cultured in Japan and Korea. Despite the relatively high production of fingerlings, some problems remain, mainly related to the larval feeding and cost of maintaining microalgae and rotifers. In order to determine the effects of different diets on the Japanese flounder larval growth and survival, a series of experiments was carried out related to the size and nutritional value of different live feeds. The larvae culture conditions were at 10 or 20 larvae/L in 50 to 2,000 L tanks, with aeration and with or without “green water,” and a temperature range of 18.5 to 22.5°C. The live foods used were microalgae (Chlorella ellipsoidea and Nannochloris oculata), baker's yeast, experimental n-yeasts, oyster trochophore larvae, three strains of rotifer Brachionus plicatilis (L-type, S-type and U-type) and Artemia nauplii. Variations were detected in size, dry weight, and chemical composition of the three strains of rotifers used. The maximum number of rotifers ingested by flounder larvae increased steadily from 7 individuals, at first feeding (3.13 mm), to 42 individuals at 5.25 mm of total length (6 days after first feeding). There was a relationship between larval total length and size of the rotifers ingested. The effect of rotifer size on larval growth and survival appeared to be limited to the first two days of feeding. Of the diets tested in the growth and survival of larval flounder during 14 days after hatching, rotifers fed on C. ellipsoidea and raised in green-water gave the best results. Rotifers cultured on enriched N. oculata and n-yeasts did not support larval growth and caused higher mortalities. The n-yeasts used as rotifer enrichment appeared to satisfy, partially, the nutritional requirement of 7-day-old flounder larvae, as did n-yeast squid wintering oil the requirements of 14-day-old larvae. From 7-9-days after hatching and throughout the second 14-day period, rotifers and Artemia cultured on N. oculata improved the survival of flounder compared with those fed on rotifers cultured on C. ellipsoidea. Moreover, the larval growth did not vary significantly between both microalgae-rotifer feedings. No clear relation was found between total protein, lipid, amino acids and fatty acids of live feeds with the growth and survival of flounder larvae, although the total lipid was higher in C. ellipsoidea than in N. oculata. The Artemia nauplii San Francisco strain appeared to be more suitable for the growth and survival of flounder larvae, than the Utah strain. The nutritional value of Artemia nauplii (Utah strain) for flounder larvae remained unchanged despite the use of either microalgae as nauplii enrichment.     

Antibacterial abilities of intestinal bacteria from larval and juvenile Japanese flounder against fish pathogens

The present study was undertaken to examine the antibacterial abilities of intestinal bacteria isolated from juveniles and larvae of Japanese flounder Paralichthys olivaceus . Newly hatched larvae of flounder were held in a 100 L plastic circular tank and fed rotifiers, Artemia nauplii and commercial feeds, depending on the developmental stage of the fish. Genera Aeromonas , Moraxella and Vibrio were predominantly isolated from the intestinal tracts of Japanese flounder at larval and juvenile stages, whereas Aeromonas , Bacillus , coryneforms, Moraxella , Pseudomonas and Vibrio were detected at high densities in live diets and artificial feeds. Antibacterial bacteria accounted for 1.7–24.3% of the intestinal isolates against Lactococcus garvieae , Pasteurella piscicida , Vibrio anguillarum and V. vulnificus . In particular, as much as 53.3% of Vibrio spp. other than Vibrio -swarmer isolated from 197-day-old juveniles inhibited the growth of P. piscicida . These results suggest that intestinal bacteria having antibacterial activity play a role in the prevention of infectious diseases.     

Qualitative and quantitative changes of F<Subscript>o</Subscript>F<Subscript>1</Subscript>-ATPase in Japanese flounder and red sea bream associated with rearing temperatures

ABSTRACT:   Fast skeletal muscles of Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major were examined for quantitative and qualitative changes of mitochondrial ATP synthase (F_oF₁-ATPase) in association with rearing temperatures. The specific activities of F_oF₁-ATPase from Japanese flounder reared at 10°C, 15°C and 25°C for 4 weeks were determined to be 81 ± 11, 74 ± 13 and 83 ± 11 nmol/min·mg mitochondrial protein, respectively. The corresponding activity from red sea bream reared at 8°C for 5 weeks was determined to be 65 ± 9 nmol/min·mg mitochondrial protein, which was higher than 33 ± 9 nmol/min·mg mitochondrial protein in fish reared at 23°C. The contents of α- and β-F₁-ATPase in total mitochondrial proteins were not significantly different between fish reared at different temperatures for the two fish species. However, the contents of β-F₁-ATPase in the total fast skeletal muscle extracts, prepared from Japanese flounder reared at 10°C, were 2.1- and 2.9-fold higher than those for fish reared at 15°C and 25°C, respectively. The corresponding content from red seabream reared at 8°C was 2.2-fold higher than that for fish reared at 23°C. Therefore, the changes in F_oF₁-ATPase depending on rearing temperatures were species-specific.     

Substrate-SDS-PAGE determination of protease activity through larval development in sea bream

Identification of alkaline proteases produced during larval stages of gilthead sea bream, Sparus aurata was achieved using SDS-PAGE and specific inhibitors. Such techniques were also applied to determine proteases existing in rotifers, Brachionus plicatilis, and Artemia nauplii, which are used as live food for these larvae, as well as proteases of adult fish. The results show a great prominence of trypsin-like proteases during the 4 weeks after hatching, but the number of enzyme species was reduced in adult fish. Alkaline proteases present in the rotifers and Artemia showed clear differences when compared with those of the larvae and were not detected in extracts obtained from fed larvae. The results obtained provide information about the role of exogenous enzymes in larval feeding of sea bream.     

延迟投饵对真鲷,牙鲆仔鱼早期阶段摄食,存活及生长的影响

试验结果表明：（１）２日龄真鲷，牙鲆仔鱼初次摄食，在６￣７日龄和５￣６日龄，不能建立外源性营养的仔鱼分别进入ＰＮＲ期，而卵黄囊均在此前１￣２天已耗尽。混合营养期分别为３￣４天和１￣２天。（２）真鲷和牙鲆仔鱼在不同饥饰饿阶段初次摄食率的变化式型是：开始较低，此后逐步上升，高峰期出现在卵黄囊接近耗尽时，此后开始下降。记录到的最高初次摄食率分别为８６．７％和３５％。（３）牙鲆仔鱼体长的增长率随延迟投饵天     

真鲷精子诱导牙鲆减数分裂雌核发育

采用真鲷精子激活牙鲆卵子,经(0±0.5)℃冷休克处理,诱导了牙鲆减数分裂雌核发育。灭活真鲷精子,紫外线照射剂量3.4mJ/cm2时孵化率最低;随着照射剂量的增加,孵化率恢复,照射剂量73mJ/cm2时,孵化率最高,呈现典型的Hertwig效应。用流式细胞仪检测倍性,未经冷休克处理的胚胎全部为单倍体,经冷休克处理的均为二倍体,表明精子灭活有效。冷休克实验结果表明,冷休克起始时间2～5min均有效,以3min为最好;冷休克持续时间30～90min均有效,以45min为最好。综合两项因素,授精3min后,休克时间持续45min组的授精率和孵化率均为最高,与其他处理组差异显著(P<0.05)。RAPD分析结果显示,异源精子的遗传信息未在雌核发育二倍体的电泳图中出现,表明其遗传信息没有传递给子代。     

Assessment of reference dietary amino acid pattern for juvenile red sea bream, <Emphasis Type="Italic">Pagrus major</Emphasis>

Four semi-purified diets, containing crystalline amino acids (CAAs), were fed to juvenile red sea bream, Pagrus major in order to ascertain the ideal dietary amino acid pattern for this species. A control diet containing 50% casein–gelatin as protein sources, but no CAAs were fed to the fish. The other diets contained 30% casein–gelatin and 20% CAAs. CAAs were added to diets to simulate with amino acid pattern of the red sea bream eggs protein (REP), red sea bream larvae whole body protein (RLP), red sea bream juvenile whole body protein (RJP), and brown fishmeal protein (BFP). The juveniles (average initial body weight, 1.58 ± 0.01 g) were maintained in triplicate tanks and fed twice daily for 30 days. The highest weight gain was observed in juveniles fed the RJP diet. No significant difference was observed in juveniles fed the RLP and BFP diet. Feed efficiency ratio, protein efficiency ratio and amino acid retention in the whole body were significantly (p < 0.05) affected by the simulated dietary amino acid patterns. The essential amino acid profile and A/E ratios of the whole body after the growth trial showed little difference among the dietary treatments. The results suggest that red sea bream juveniles are able to utilize high amounts of CAA in coated form. The amino acid pattern of RJP could be used as an appropriate of reference dietary amino acid for this species.     

Effects of dietary mannan oligosaccharides in early weaning diets on growth,survival, fatty acid composition and gut morphology of gilthead sea bream (Sparus aurata,L.) larvae

Early weaning of marine fish larvae with dry diets delays gut maturation and reduces growth rates. In juvenile and adult forms of several marine fish species, inclusion of dietary mannan oligosaccharides (MOS) improves gut integrity and functionality, but the effects of MOS inclusion in gilthead sea bream (Sparus aurata, L.) larval diets have not been addressed yet. Thus, this study assesses the effects of dietary MOS inclusion on survival, growth performance, gut morphology, feed acceptance and quality of gilthead sea bream larvae. For that purpose, 16 days post‐hatched gilthead sea bream larvae were fed four graded levels of MOS (Biomos^®, Alltech, Nicholasville, KY, USA) in weaning diets as follows: 0 g kg^?1 MOS, 0.5 g kg^?1 MOS, 1.5 g kg^?1 MOS and 2 g kg^?1MOS. Dietary MOS did not affect feed acceptance in gilthead sea bream larvae (P > 0.05). MOS supplementation was correlated in a dose‐dependent way with higher larval survival (P = 0.026). After 15 days of feeding, dietary MOS increased whole larvae (P < 0.01) arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Gilthead sea bream larvae fed 2 g kg^?1 MOS presented higher gut occupation with goblet cells after feeding compared with larvae fed the other dietary treatments. Overall, the results suggest that inclusion of MOS in early weaning diets for gilthead sea bream improves essential fatty acid utilization and may promote growth and final survival.     

Studies on the green liver in cultured red sea bream fed low level and non-fish meal diets: Relationship between hepatic taurine and biliverdin levels

SUMMARY: The aim of this study was to investigate the cause of green liver in red sea bream fed substitute protein diets. Red sea bream Pagrus major was given either of the following diets for 28 weeks: (1) control diet (50% fish meal), (2) low level fish meal diet (15% fish meal), and (3) non-fish meal diet (0% fish meal). The green liver was observed in all groups tested, but the incidence was much higher in the experimental diet groups. The feeding of substitute protein diets reduced plasma triglyceride and cholesterol levels. However, there was no significant difference in plasma hepatic enzyme activities and plasma bile salts concentration among the treatments. Fish fed the substitute protein diets showed low hepatic taurine levels with an appearance of a biliverdin in the liver. Moreover, the proportion of ditaurobilirubin to total biliary bile pigments was significantly lower in fish fed the substitute protein diets. These data indicate that feeding of substitute protein diets did not induce any cholestatic hepatobiliary obstructions and that the low hepatic taurine level was one of the probable factors responsible for the occurrence of green liver in red sea bream fed substitute protein diets.     

The use of preserved copepods in sea bream small‐scale culture: biometric,biochemical and molecular implications

Considering the well‐known problems arising from the use of rotifers and Artemia as live prey in larval rearing in terms of fatty acid deficiencies, the aim of this study was to evaluate a partial or complete replacement of traditional live prey with preserved copepods during the larviculture of gilthead sea bream (Sparus aurata). Sea bream larvae were randomly divided into 4 experimental groups in triplicates: group A larvae (control) fed rotifers followed by Artemia nauplii; group B fed a combined diet (50%) of rotifers–Artemia and preserved copepods; group C fed rotifers followed by preserved copepods; and group D fed preserved copepods solely. Survival and biometric data were analysed together with major molecular biomarkers involved in growth, lipid metabolism and appetite. Moreover, fatty acid content of prey and larvae was also analysed. At the end of 40 days treatment, a stress test, on the remaining larvae, was performed to evaluate the effects of different diets on stress response. Data obtained evidenced a positive effect of cofeeding preserved copepods during sea bream larviculture. Higher survival and growth were achieved in group B (fed combined diet) larvae respect to control. In addition, preserved copepods cofeeding was able to positively modulate genes involved in fish growth, lipid metabolism, stress response and appetite regulation.     

Lordotic Deformation and Abnormal Development of Swim Bladders in Some Hatchery-Bred Marine Physoclistous Fish in Japan

At many hatcheries in Japan, a high incidence of lordosis is being reported among marine physoclistous juveniles of red sea bream, Japanese sea bass, and amberjack. Extensive studies being conducted since 1975 to tackle this problem have led to the following conclusions, and effective countermeasures are being proposed.
During early larval development in the temporary physostomous stage, fish must be able to gulp air at the water surface for normal development of the swim bladder. The juveniles that fail to gulp air swim upward in an oblique position because of insufficient buoyancy, causing the backbone to curve in a V-shape.
The managerial solutions proposed are: 1) reduce the strong water current caused by vigorous aeration; 2) provide nutrient-enriched rotifers to produce healthy swimming larvae; and 3) prevent any oily film formation on the water surface.     

Interactive effects of dietary vitamin C and phospholipid in micro‐bound diet for growth,survival, and stress resistance of larval red sea bream,Pagrus major

This study was conducted to examine the effects of dietary ascorbic acid (AsA) and phospholipid (PL) and their interaction on growth, survival, and stress resistance in red sea bream larvae. Twenty‐six days old red sea bream were fed nine micro‐bound diets supplemented three levels of AsA (0, 800 and 1600 mg kg^?1 diet) and PL (0, 20 and 40 g kg^?1 diet) for 15 days. Dietary AsA and PL were both significant factors on survival rates. There was also an interaction between dietary AsA and PL on survival rate (P < 0.05). The larvae fed 800 or 1600 mg kg^?1 AsA with 40 g kg^?1 PL diets showed the highest survival rate, with values similar to those of the live‐food supplemented group. Stress resistance against low salinity exposure significantly increased with increased dietary level of AsA and PL. However, significant interaction of AsA and PL was not detected. The larvae fed 1600 mg kg^?1 AsA with 40 g kg^?1 PL diet showed the highest stress resistance among all diets, but it was not significantly different than that of larvae fed 800 mg kg^?1 AsA with 40 g kg^?1 PL diet. This study clearly demonstrated that combined use of AsA and PL can improve survival of 26–40 days posthatching red sea bream larvae. Moreover, the present study suggested that 800 mg kg^?1 AsA with 40 g kg^?1 PL in diet was needed for producing high quality seedling under the stressful conditions.