Dietary histidine requirement of juvenile blunt snout bream (Megalobrama amblycephala)

An eight‐week feeding trial was conducted to determine the dietary histidine requirement of juvenile blunt snout bream. The results showed that final body weight, weight gain rate and specific growth rate significantly increased with increasing dietary histidine levels up to 9.9 g/kg (p < .05) and decreased gradually thereafter, while feed conversion ratio showed a converse trend. The survival rate, condition factor, viscerosomatic and hepatosomatic index were not significantly affected by the graded dietary histidine levels (p > .05). About 9.9 g/kg dietary histidine level significantly improved whole‐body protein and lowered moisture content. The contents of plasma total protein, cholesterol, urea and triglyceride levels were not significantly affected by dietary histidine levels. About 9.9 g/kg dietary histidine level significantly upregulated target of rapamycin and insulin‐like growth factor mRNA levels (p < .05), and 12.1 g/kg and 14.2 g/kg dietary histidine levels significantly upregulated eukaryotic translation initiation factor 4E‐binding protein 2 and ribosomal protein S6 kinase‐polypeptide 1 mRNA levels (p < .05). Based on second‐degree polynomial regression analysis of weight gain rate, and specific growth rate against dietary histidine levels, the dietary histidine requirement for juvenile blunt snout bream was estimated to be 11.2 g/kg of diet, corresponding to 36.1 g/kg of dietary protein.     

Alterations of liver histology and blood biochemistry in blunt snout bream Megalobrama amblycephala fed high-fat diets

In this study we examined the effects of high-fat diets on alterations in liver histology features and blood biochemistry parameters in blunt snout bream Megalobrama amblycephala. Fish were fed three diets containing 5, 10, and 15 % fat, respectively, for 6 weeks prior to the liver histology examination and blood biochemistry testing. The livers of fish fed the 5 % fat diet showed a normal structure, whereas those of the fish fed the diets with a higher fat content presented nucleus polarization and lipid vacuolization. Transmission electron microscopy examination revealed that the hepatocytes of fish fed the 15 % fat diet had undergone ultrastructural alterations involving the mitochondria, nucleus, and endoplasmic reticulum (ER). Alterations in the blood biochemistry were evaluated to determine whether the blood biochemistry changes could be correlated with the observed alterations in liver histology with the aim of assessing the suitability of the investigated blood parameters as rapid indicators of liver condition. Significantly higher levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and of triglycerides and cholesterol were found in fish fed the 15 % fat diet. On the whole, the results clearly show that high fat intake resulted in fat accumulation and ultrastructural impairments of the mitochondria, nucleus, and ER. We conclude that blood sample measurements (AST, ALT, triglycerides, and cholesterol) could be used as a rapid test for determining liver status in blunt snout bream.     

Dietary methionine requirement of juvenile blunt snout bream (Megalobrama amblycephala) at a constant dietary cystine level

A 9‐week feeding trial was conducted to investigate the dietary methionine requirement of juvenile Megalobrama amblycephala at a constant dietary cystine level. Six semipurified diets were formulated to contain graded dietary methionine levels from 3.9 to 15.4 g kg^?1 in about 2.5 g kg^?1 increments in the presence of 2.2 g kg^?1 cystine. Results showed that specific growth rate (SGR) and protein efficiency ratio (PER) significantly increased with increasing dietary methionine levels from 3.9 to 12.4 g kg^?1 and thereafter kept stable. Maximum protein productive value (PPV), nitrogen retention efficiency (NRE) and liver weight were observed in 8.5 g methionine kg^?1 diet. Protein contents in whole fish body were positively correlated with dietary methionine level, while lipid contents were negatively correlated with it. Morphological index and hepatic glutamate‐pyruvate transaminase (GPT) activities were independent of dietary methionine levels. However, dietary methionine supplementation significantly improved haematological parameters, plasma methionine and total essential amino acid contents and hepatic glutamate‐oxaloacetate transaminase (GOT) activities. Analysis of dose response using broken‐line regression on the basis of SGR and PPV versus dietary methionine level estimated the optimum dietary methionine requirements of juvenile M. amblycephala to be between 8.5 and 8.4 g kg^?1 of diet (25.0 and 24.7 g kg^?1 of protein) in the presence of 2.2 g kg^?1 cystine, respectively. Hence, the corresponding total sulphur amino acids requirements of this species were calculated to be 10.7 and 10.6 g kg^?1 of diet (31.5 and 31.2 g kg^?1 of dietary protein).     

Effects of dietary supplementation of fructooligosaccharide on growth performance,body composition,intestinal enzymes activities and histology of blunt snout bream (Megalobrama amblycephala) fingerlings

A feeding trial was conducted to investigate the effects of dietary fructooligosaccharide (FOS) on growth performance, body composition, intestinal enzymes activities and histology of fingerling Megalobrama amblycephala. A total of 1200 fish (1.42 ± 0.01 g) were fed diets containing graded levels of FOS (0, 0.5, 1, 2, 4 and 8 g kg⁻¹ diet) for 8 weeks in a recirculating system indoor. The weight gain, specific growth rate (SGR) and survival rate were all improved in dietary supplementation of FOS fed fish. Increasing FOS levels resulted in both higher whole‐body lipid and lower moisture contents, whereas ash and protein contents showed no significant differences among all the treatments. Intestinal amylase, protease, Na⁺, K⁺‐ATPase, alkaline phosphatase, γ‐glutamyl transpeptidase and creatine kinase activities all increased with dietary FOS levels up to 4 g kg⁻¹ (P < 0.05). Transmission electron microscopy analysis indicated that microvilli length in the mid‐intestine was significantly increased with increased dietary FOS levels (P < 0.05). In conclusion, dietary supplementation of FOS could confer benefits on growth performance, intestinal digestive and absorptive ability, histology of fingerling Megalobrama amblycephala.     

湖北淤泥湖团头舫mtDNA限制性片段长度多态性的研究

用ＢａｍＨＩ、ＢｇｌＩ、ＣｌａＩ、ＥｃｏＲＩ、ＨｉｎｄⅢ、ＫｐｎＩ、ＰｓｔＩ，ＰｖｕⅡＳａｃⅡ、ＳａｃＩ、ＳｃａＩ、ＸｂａＩ，ＸｂａＩ和ＸｈｏＩ十四种限制性内切酶对来源于湖北淤泥湖的团头舫进行线粒体ＤＮＡ限制性片估长度多态性研究。初步表明ＤＮＡ上切点呈现不同程度的多态性。共检测到六种母集集团。发现一尾团头舫ｍｔＤＮＡ分子大小比普通型鱼ｍｔＤＮＡ小约０．７０ｋｂ。呈现出ｍｔＤＮＡ发子大小多态现象。     

饲料锌对团头鲂幼鱼生长性能、血清生化指标和抗氧化功能的影响

以酪蛋白和明胶为蛋白源,七水硫酸锌(Zn SO4·7H2O)为Zn源,分别配制成7种Zn含量(7.4 mg/kg、20.3 mg/kg、32.1 mg/kg、51.0 mg/kg、84.4 mg/kg、169.7 mg/kg、332.4 mg/kg)的半纯化饲料,投喂初始体重为(3.6±0.1)g团头鲂(Megalobrama amblycephala)12周,考察Zn对团头鲂幼鱼生长性能、血清生化指标和抗氧化功能的影响,确定团头鲂幼鱼对饲料Zn的需要量。结果表明,随着饲料Zn含量增加,团头鲂增重率、特定生长率和全鱼Zn含量呈先增加后稳定的趋势;全鱼水分含量显著降低(P0.05),粗蛋白含量显著增加。饲料Zn含量对团头鲂饲料系数无显著影响。饲料中添加Zn显著影响血清总蛋白、尿素氮、高密度脂蛋白胆固醇、总胆固醇以及甘油三酯含量,而对血清白蛋白含量和碱性磷酸酶活性无显著影响。随着饲料中Zn含量的增加,团头鲂肝丙二醛含量显著降低(P0.05),而肝过氧化氢酶和超氧化物歧化酶活性在各处理间均无显著差异。折线回归分析表明,团头鲂幼鱼(体重3.6~26.7 g)获得最佳生长时对饲料Zn需要量为32.6 mg/kg,获得最大鱼体Zn含量时Zn的需要量为47.6 mg/kg。本研究旨在确定团头鲂幼鱼对饲料中Zn的需要量,为配制团头鲂高效环保饲料提供科学依据。     

苯磷硫胺对饲喂高糖饲料团头鲂血浆生化指标及肝糖脂代谢的影响

为了探究苯磷硫胺对饲喂高糖饲料团头鲂(Megalobrama amblycephala)的血清生化指标及肝糖脂代谢的影响,随机选取360尾体重(45.25±0.34)g的团头鲂幼鱼,进行12周的养殖实验,期间分别投喂6种饲料[对照组C:30％糖水平;高糖组HC:43％糖水平;高糖组+不同苯磷硫胺添加量:43％糖水平+0...     

Effects of dietary docosahexaenoic acid on growth performance,fatty acid profile and lipogenesis of blunt snout bream (Megalobrama amblycephala)

Six diets were designed to investigate the effects of dietary docosahexaenoic acid (22:6n‐3; DHA) levels (0.5, 1.3, 2.3, 4.2, 8.1 and 15.9 g/kg diets) on growth performance, fatty acid profile and expression of some lipogenesis‐related genes of blunt snout bream (Megalobrama amblycephala). Fish (average weight: 26.40 ± 0.11 g) were randomly fed one of six diets for 8 weeks. Results indicated that the final body weight (FBW) and specific growth rate (SGR) of fish fed 1.3 g/kg DHA were significantly higher than other groups except for the 2.3 g/kg DHA (p < .05). Compared with other groups, the number of lipid droplet clusters of the liver stained with oil red O in the 2.3 g/kg DHA group was the highest, which was consistent with the lipid contents of whole body and liver. The DHA proportion in liver and muscle significantly increased with the increasing dietary DHA levels (p < .05), which reflected fatty acid profiles of diets. The highest mRNA expressions of acetyl‐CoA carboxylase α (ACCα), fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP‐1) occurred in the 1.3 g/kg DHA group, followed by 2.3 g/kg DHA. In summary, the supplementation of 1.3–2.3 g/kg DHA could improve growth performance and lipogenesis, and the dietary DHA could improve DHA and PUFA proportion in liver and muscle.     

Effects of dietary carbohydrate/lipid ratios on growth performance,body composition and glucose metabolism of fingerling blunt snout bream Megalobrama amblycephala

This study aimed to investigate the optimum dietary carbohydrate/lipid (CHO/L) ratio for fingerling blunt snout bream Megalobrama amblycephala (average initial weight: 6.61 ± 0.03 g). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO/L ratios ranging from 1.62 to 24.20. Each diet was tested in four replicates for 10 weeks. Specific growth rate (SGR), feed conversion ratio and nitrogen and energy retention all improved significantly (P < 0.05) as dietary CHO/L ratios decreased from 24.20 to 5.64 but showed little difference (P > 0.05) as dietary CHO/L ratios ranged from 2.45 to 5.64. Hepatosomatic index increased significantly (P < 0.05) as dietary CHO/L ratios increased, whereas intraperitoneal fat ratio showed an opposite trend (P < 0.05). Opposite to moisture content, lipid content of whole body and carcass all increased significantly (P < 0.05) as dietary CHO/L ratios decreased. Liver lipid content showed little difference (P > 0.05) among all the treatments, while liver glycogen content increased significantly (P < 0.05) with increasing CHO/L ratios. High dietary carbohydrate enhanced the activities of liver hexokinase, pyruvate kinase and glucose‐6‐phosphate dehydrogenase but did not induce hyperglycaemia. Based on the second‐order polynomial regression analysis of SGR, the optimal dietary carbohydrate and lipid contents for fingerling blunt snout bream were 291.7 and 81.4 g kg⁻¹, respectively, with a corresponding dietary CHO/L ratio of 3.58.     

不同倍性团头鲂群体的线粒体DNA 分析

测定了来自5个不同倍性团头鲂（Megalobrama amblycephala）群体（4n-F1、正交3n、反交3n、异源3n、二倍体2n）57个个体的线粒体DNA控制区、细胞色素b基因、16S rRNA基因和COⅡ基因序列,通过对这4段基因序列的联合分析,研究了5个不同倍性团头鲂群体的遗传变异。这4个基因片段的长度分别为：控制区937bp,细胞色素b基因1140bp,16S rRNA基因片段564bp,COⅡ基因片段642bp。将4个基因片段合并为1条总长度为3283bp的片段：在这条3283bp片段中,T、C、A、G4种核苷酸的平均含量分别为27．18％、25．45％、30．71％、16．66％。57个个体中确定了55种单倍型,未发现群体间有共享的单倍型,五群体的单倍型多样度在0．9848-1．0000之间,显示不同倍性团头鲂群体内单倍型类型丰富。5个群体内各序列平均核苷酸差异数（目在8．000-24．273之间,核苷酸多样性指数（π）在0．2483％～0．7866％之间：群体间遗传距离范围为0．0039～0．0106,显示不同倍性团头鲂群体遗传多态性丰富。核苷酸多样性指数（π）、平均核苷酸差异数（K）和核苷酸序列间平均遗传距离在5个群体间的变化趋势一致,由大到小依次为反交3n、异源3n、正交3n、同源4n-F1、二倍体2n。而且,反交3n、异源3n、正交3n和同源4n-F1群体的核苷酸多样性指数（π）、平均核苷酸差异数（K）以及核苷酸序列间平均遗传距离均显著大于2n群体（P〈0．05）。结果表明,反交3n、异源3n、正交3n和同源4n-F1群体的遗传多样性水平显著高于2n群体。[中国水产科学,2008,15（2）：222-229]     

果寡糖对急性氨氮应激下团头鲂非特异性免疫指标的影响

为研究氨氮应激条件下果寡糖对团头鲂(Megalobrama amblycephala)非特异免疫指标的影响,试验选择360尾初重为13.5 g的团头鲂随机分为3组,每组4个重复,每缸30尾鱼,对照组投喂基础日粮,试验组分别投喂果寡糖(FOS)添加量为0.4%和0.8%的日粮,饲养8周,养殖试验结束后,用10 mg/L的NH4Cl对24尾鱼进行氨氮应激试验。试验结果显示,氨氮应激前,0.4%FOS组的血液谷丙转氨酶(GPT)活性显著低于对照组和0.8%FOS组,在氨氮应激后,0.4%FOS组的GOT活性有降低的趋势,但仅在24 h时显著低于0.8%组,0.8%组和对照组之间并无显著差异;血清酸性磷酸酶、补体3(C3)、补体4(C4)、酚氧化酶都出现先升高后降低的趋势,分别在应激后的3、24、12、12 h达到最大值。此外,应激前0.4%FOS组补体C3、C4、酚氧化酶的活性都显著高于对照组,应激后0.4%FOS组C3在3 h处显著高于对照组,但是在其它时间点各组差异并不显著,果寡糖添加水平和采样时间对这些免疫指标都无显著的交互作用。结果表明饲料中添加0.4%的果寡糖能够提高团头鲂的免疫力指标活性,提高了团头鲂抗氨氮应激的能力。     

Essential amino acids supplementation to practical diets affects growth,feed utilization and glucose metabolism‐related signalling molecules of blunt snout bream (Megalobrama amblycephala)

Six diets were formulated to investigate the success of fish meal (FM) replacement by plant proteins; diet 1 reflected a commercial feed (8% FM), diet 3 contained 4% FM, and diet 5 was devoid of FM. Whereas, diet 2, diet 4, and diet 6 reflected diet 1, diet 3, diet 5, respectively, and supplemented with essential amino acid (EAA). At the end of 8‐week trial, there was no significant difference in survival rate. Significantly higher final weight, weight gain rate, and specific growth rate were recorded in the group fed diet 2 compared with the other treatments (except diet 4) (p < 0.05). Feed conversion ratio of fish fed diet 2 was significantly lower than those fed diets 1, 3, and 5 (p < 0.05). The lowest feed intake and highest protein efficiency rate were found in fish fed diet 2 (p < 0.05). There was no significant difference in whole body compositions between treatments. Plasma aspartate transaminases, alanine aminotransferase, and glucose were significantly affected by dietary treatments (p < 0.05), while plasma protein and albumin contents were not influenced by the treatments. The relative expression of target of rapamycin (TOR) and phosphatidylinositol 3‐kinase, regulatory subunit 1 (alpha) (PIK3R1) in fish fed diet 3 (4% FM) were significantly down‐regulated compared with those fed diet 6 for TOR and diets 4 and 6 for PIK3R1 (p < 0.05). Insulin receptor substrate 1 (IRS‐1) and janus kinase 3 (JAK3) expressions were fluctuated, with the higher levels in fish fed diets 4 and 6. In conclusion, the findings of this study indicate that plant protein mixture supplemented with EAA could be used to substitute FM in practical diet for Megalobrama amblycephala.     

Establishment and characterization of a fin cell line from blunt snout bream, Megalobrama amblycephala

This study established and characterized a new cell line (MAF) from the fin of blunt snout bream (Megalobrama amblycephala), a freshwater fish cultivated in China. MAF cells proliferated well in medium 199 supplemented with 10 % fetal bovine serum at 28 °C and have been subcultured more than 95 times in almost a year. MAF cells were revived at 90–95 % viability after 3–6 months of storage in liquid nitrogen. Karyotyping indicated that the modal chromosome number of MAF cells was 48. The MAF cell line consisted predominantly of fibroblastic and epithelial-like cells from M. amblycephala, which was confirmed by immunofluorescence and mitochondrial 12s rRNA sequencing. Viral susceptibility tests showed that MAF cells were susceptible to infection by snakehead rhabdovirus, spring viremia carp virus, and channel catfish virus, which was demonstrated by the presence of cytopathic effect, high viral titers, and PCR products. Bacterial cytotoxicity studies showed that extracellular products from Aeromonas hydrophila were toxic to MAF cells. Cu²⁺ was also cytotoxic to MAF cells, and the 24-h IC₅₀ value was 144.48 μmol/l. When MAF cells were transfected with pEGFP-N1 plasmid, bright fluorescent signals were observed, and the transfection efficiency reached up to 5 %. These results suggest that the MAF cell line may provide a valuable tool for studying virus pathogenesis, as well as cytotoxicity testing and genetic manipulation studies.     

Complete replacement of fish meal by plant protein ingredients with dietary essential amino acids supplementation for juvenile blunt snout bream (Megalobrama amblycephala)

Six extruded diets were formulated with a graded level of fish meal (FM); diet 1 and diet 2 were formulated with 80 g/kg FM; diet 3 and diet 4 were formulated with 40 g/kg FM; and diet 5 and diet 6 were devoid of FM. Hence, diet 2, diet 4 and diet 6 were supplemented with essential amino acids (EAAs). The diets were fed throughout an eight‐week feeding trial. The results revealed that specific growth rate (SGR), feed conversion ratio (FCR), body weight gain (BWG) and protein efficiency ratio (PER) were influenced by FM reduction and improved by the addition of EAA (p < 0.05). A survival rate (SR), whole body content of protein, lipid, moisture and ash, and plasma total protein (TP), albumin (ALB), triglyceride (TG) and urea (UN) did not influence by dietary treatments (p > 0.05). Additionally, target of rapamycin (TOR) pathway did not influence by dietary treatments (p > 0.05). Expression levels of hepatic peptide transporter 1 (Pept1) and peptide transporter 2 (Pept2) decreased against FM reduction and improved significantly in the groups fed diet 4 and diet 6. In summary, the findings revealed that diet containing plant proteins mixture supplemented with EAA could totally replace FM in the practical diet of blunt snout bream.     

团头鲂3个选育群体遗传潜力的微卫星分析

为从遗传多样性的角度了解团头鲂(Megalobrama amblycephala)3个选育群体的遗传潜力,该研究以团头鲂"浦江1号"选育奠基群体(F_0)为对照组,采用14个多态性转录组微卫星标记评估了团头鲂3个选育群体的遗传多样性,分析其遗传潜力。结果显示,3个选育群体平均每个位点的等位基因数(A)为7.928 6~8.785 7,有效等位基因数(A_E)为4.409 4~4.878 4,观察杂合度(H_O)为0.491 1~0.574 4,期望杂合度(HE)为0.741 3~0.751 8,多态信息含量(PIC)为0.691 2~0.705 2,近交系数(FIS)为0.229~0.352。3个选育群体的遗传多样性水平(AE、HE)均高于F0群体,但不存在显著差异(P0.05)。3个选育群体的有效群体大小(N_e)为11.0~29.3,在近期可能经历过遗传瓶颈。3个选育群体间D_A、D_(SW)遗传距离分别为0.175 4~0.358 8、0.804 7~1.054 4。该结果表明,3个选育群体的遗传多样性较高,遗传潜力较大,但因有效群体数量较少和瓶颈效应的影响,存在杂合度下降和近交衰退的风险,今后需采取科学措施来保护选育群体的遗传潜力。     

团头鲂同源四倍体、倍间三倍体与二倍体红细胞的形态特征比较

通过比较同源四倍体、倍间三倍体与二倍体团头鲂（Megalobrama amblycephala）的红细胞、红细胞核的形态大小差异,探讨不同倍性团头鲂的红细胞形态遗传特征。结果表明：（1）团头鲂多倍体（同源4n和倍间3n）的红细胞数量显著低于二倍体（2n）团头鲂（P〈0．05）。其中,倍间三倍体团头鲂每毫升血液的红细胞数为二倍体的78．95％,而同源四倍体的红细胞数量下降幅度较大,仅为2n团头鲂的56．87％。（2）团头鲂同源四倍体、倍间三倍体的红细胞短径和长径、核短径和长径、红细胞表面积、红细胞体积和核体积均依倍性增加而显著增大（P〈0．05）;其中,又以核体积增大最为显著,同源四倍体、倍间三倍体的核体积分别为2n团头鲂的1．97倍和1．39倍。（3）团头鲂同源四倍体每毫升血液红细胞的总体积和总表面积,均明显低于二倍体和倍间三倍体团头鲂（P〈0．05）;倍间三倍体每毫升血液红细胞的总体积要多于二倍体团头鲂（P〈0．05）,但红细胞的总表面积在倍间三倍体与二倍体团头鲂间不存在显著差异（P〉0．05）。（4）在团头鲂同源四倍体中还观察到一定比例的异常红细胞现象。     

Anti-stress properties and two HSP70s mRNA expressions of blunt snout bream (Megalobrama amblycephala) fed with all-plant-based diet

The influence of all-plant-based diet on fingerling blunt snout breams (Megalobrama amblycephala) was tested by examining growth performance, anti-stress properties and related gene expression. Healthy fish were randomly divided into triplicate groups per dietary treatment and fed with different formulated diets. The results showed that both weight gain, specific growth rate and protein efficiency ratio of all-plant-based diet group were significant higher than those of the control (p < 0.05). In contrast, FCR of all-plant-based diet group was significantly lower than that of the control (p < 0.05). Therefore, all-plant-based diets could not affect the growth performance of blunt snout breams. Compared to the control group, the lysozyme levels in serum and mucus, and glutamic-oxaloacetic transaminase activities in serum and liver decreased significantly (p < 0.05). In contrast, the glutamic-pyruvic transaminase activities in serum and liver increased significantly (p < 0.05). For blunt snout breams fed with all-plant-based diets, the superoxide dismutase activities in mucus, serum and liver as well as catalase activity in serum and liver were decreased significantly (p < 0.05) comparing with that of the control group. But malondialdehyde contents were higher (p < 0.05) in serum and liver than that of control group. The expression of HSC70 mRNA increased significantly (p < 0.05) in blunt snout breams fed with all-plant-based diet, whereas the HSP70 mRNA expression decreased significantly (p < 0.05) when compared with control group. In conclusion, all these results indicated that the application of all-plant-based diet could decrease the anti-stress properties (non-specific immunity, stress resistance and antioxidant ability) and HSP70 mRNA expression in blunt snout breams fingerling. Although all-plant-based diets could not affect the growth performance of blunt snout breams, the application of all-plant-based diet should be discreet in the production practice.     

Effects of stocking density on the growth performance,digestive enzyme activities,antioxidant resistance,and intestinal microflora of blunt snout bream (Megalobrama amblycephala) juveniles

In this study, effects of stocking density on the growth performance and physiological responses of blunt snout bream, Megalobrama amblycephala juveniles were evaluated. The fish (average body weight, 25.76 ± 2.25 g) were randomly stocked at densities of 30F (30 fish/m³), 60F, 90F and 120F in 12 cages (1 m × 1 m × 1 m) in a concrete pond, with three cages for each density, for a period of 6 weeks. The higher stocking densities had a negative effect on individual growth performance. The results indicated that serum cortisol, triglyceride, alanine aminotransferase, aspartate transaminase, alkaline phosphatase and malondialdehyde activities; and Acinetobacter, Aeromonas, Pseudomonas and Vibrio numbers in the intestinal microflora increased significantly as the stocking density increased. In contrast, the viscerosomatic index, hepatosomatic index survival rate; serum glucose, total cholesterol, lipase, protease, glutathione peroxidase and superoxide dismutase activities; and Clostridium, Bacteroides, Lactococcus, Lactobacillus and Bacillus numbers in the intestinal microflora decreased significantly. The 90F and 120F groups showed obvious enlargement of the lamina propria and goblet cell damage, indicating that the gut showed inflammatory responses. The specific growth rate and weight gain rate increased significantly as the stocking density increased from 30 to 60 fish/m³, but decreased significantly when the stocking density was over 60 fish/m³.