不同蛋白源饲料对褐点石斑鱼幼鱼血细胞发生的影响

以全鱼粉作为唯一蛋白源(D1),用豆粕替代10%、20%鱼粉(D2、D3),玉米蛋白粉替代10%鱼粉(D4),啤酒酵母替代10%鱼粉(D5),配制5组等氮等能饲料,每种饲料设置3个实验组,进行56 d的养殖实验。通过血液和组织涂(印)片、细胞染色和显微观察,研究人工培育的褐点石斑鱼幼鱼外周血液白细胞的分类组成,头肾、脾脏、体肾和肝脏等4种组织中各类血细胞的发生情况,以及不同蛋白源饲料对褐点石斑鱼血细胞发生的影响。结果表明:褐点石斑鱼外周血液中的白细胞由淋巴细胞(53.30%±4.66%)、血栓细胞(35.69%±3.85%)、嗜中性粒细胞(10.34%±3.14%)、单核细胞(0.28%±0.36%)、浆细胞(0.24%±0.34%)和嗜酸性粒细胞(0.15%±0.27%)组成;组织印迹片中,未成熟的红细胞、淋巴细胞和粒细胞主要在头肾印迹片中出现,未成熟的单核细胞主要在头肾和脾脏印迹片中出现,血栓细胞在肝脏印迹片中数量最多,推断褐点石斑鱼幼鱼主要的造血组织是头肾,其次是脾脏;在4种组织中均观察到浆细胞,在体肾印迹片中观察到嗜碱性粒细胞,在肝脏印迹片中观察到巨噬细胞,在头肾印迹片中还观察到巨大原红细胞。显微观察和数据统计分析的结果都表明,投喂5种蛋白源不同的配合饲料,未对褐点石斑鱼4种组织中血细胞的发生情况造成显著影响。     

Effects of Dietary Stachyose on Growth Performance,Digestive Enzyme Activities and Intestinal Morphology of Juvenile Turbot(Scophthalmus maximus L)

A 12-week feeding trial was conducted to evaluate the effects of dietary stachyose on the growth performance, digestive enzymes activities and intestinal structures of juvenile turbot(Scophthalmus maximus L). Five isonitrogenous(49.58% crude protein) and isolipidic(10.50% crude lipid) diets were formulated to contain 0(Control), 0.625%(S-0.625), 1.25%(S-1.25), 2.5%(S-2.5) and 5%(S-5) stachyose, respectively. With the increase of stachyose level, the growth performance and feed utilization of turbot, such as the specific growth rate, final mean body weight, weight gain rate and feed efficiency, increased significantly(P 0.05) and then stabilized. The feed intake of fish fed S-5 was significantly higher(P 0.05) than that of fish in other groups. The activities of trypsin, intestinal caseinolytic, stomach and intestinal amylase were significantly influenced by stachyose(P 0.05). The highest values of trypsin and intestinal caseinolytic activities were observed in group S-1.25, while the highest activity of stomach amylase and the lowest activity of intestine amylase were observed in group S-5. No lesion or damage was found on the distal intestine structures of fish from all treatments, while the height of simple folds in the distal intestine was significantly increased(P 0.05) when 1.25% or 2.5% stachyose was added in the diets. These results indicated that moderate level of stachyose(1.25%) improves the growth performance, feed utilization, digestive enzyme activities and the distal intestine structures of juvenile turbot.     

Effects of a low-radiotoxicity uranium salt(uranyl acetate) on biochemical and hematological parameters of the catfish,Clarias gariepinus

Specimens of Clarias gariepinus were treated with lethal(70,75,80,85,90,and 95 mg/L) and sub-lethal concentrations(8,12 and 16 mg/L) of uranyl acetate,a low-radiotoxicity uranium salt. The LC 50 value was registered as 81.45 mg/L. The protein and glycogen concentrations in liver and muscles were decreased in the fish exposed to sub-lethal concentrations. The red blood cell(RBC) and white blood cell(WBC) counts,haemoglobin(Hb) concentration and haematocrit(Hct) values were decreased. Different blood indices like mean corpuscular volume(MCV),mean corpuscular haemoglobin(MCH) and mean corpuscular haemoglobin concentration(MCHC) were negatively affected. Level of plasma glucose was elevated whereas protein was decreased. The level of calcium concentration(Ca) was declined in the blood of exposed fish whereas magnesium(Mg) remains unchanged. The activity level of glutamic-oxaloacetic transaminase(GOT) and glutamic-pyruvic transaminase(GPT) was elevated in exposed fish. These effects were more pronounced in the last period of exposure and in higher concentrations. Results of the present study indicate that uranyl acetate has adverse effects on C larias gariepinus and causes changes in the biochemical and hematological parameters of the fish.     

3-甲基胆蒽对斑马鱼组织病理效应的初步研究

分别用25、50、100、200和400μg/L的3-甲基胆蒽(3-MC)对斑马鱼进行水浴染毒,于第7天和第14天采集各染毒组和对照组活鱼的肝、鳃、心、肠和肾,进行病理组织学检查。结果发现,一定剂量的3-MC能导致肝细胞变性,胞浆内出现脂肪滴,严重时肝细胞坏死解体,界限模糊;心肌细胞萎缩坏死;肠粘膜上皮细胞纹状缘不整齐,有的脱落;鳃丝结构异常,鳃小片表面粗糙,上皮细胞不完整;肾小管上皮细胞肿胀,细胞界限不清,管腔内均质红染。供试斑马鱼的病理组织变化与3-MC的作用剂量和作用时间存在一定的关系。     

溶藻弧菌胞外产物注射赤点石斑鱼后的组织病理学观察

在注射溶藻弧菌胞外产物(ECP)48 h后,石斑鱼Epinephelus akaara出现死亡,临床症状表现为:运动迟缓,体色变深,腹部膨大,腹腔有明显的积水,肝脏出血有花斑,肾脏和脾脏肿大。病理组织切片观察发现:肝细胞坏死,解体,界限模糊,细胞核变形、裂解甚至消失;肝脏出血,肝索中有红细胞浸润,有的红细胞变形甚至破裂;肾小管上皮细胞脱落、坏死;肠粘膜上皮细胞脱落、坏死,微绒毛不整齐,模糊不清,脱落;脾窦和脾索不清晰,分界不清,且在脾窦和脾索中分布着大量的、形态不规则的红细胞。此外,还发现在肝脏、脾脏、肾脏、肠壁肌层、心肌和鳃等组织中存在一种相同结构,该结构有平滑肌环绕,管腔内壁衬以扁平上皮细胞,管腔中含有一团染成紫红色的物质,经推断为小动脉透明样变性,而在正常的组织切片中,均无此结构。     

Effects of a low-radiotoxicity uranium salt (uranyl acetate) on biochemical and hematological parameters of the catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis>

Specimens of Clarias gariepinus were treated with lethal (70, 75, 80, 85, 90, and 95 mg/L) and sub-lethal concentrations (8, 12 and 16 mg/L) of uranyl acetate, a low-radiotoxicity uranium salt. The LC 50 value was registered as 81.45 mg/L. The protein and glycogen concentrations in liver and muscles were decreased in the fish exposed to sub-lethal concentrations. The red blood cell (RBC) and white blood cell (WBC) counts, haemoglobin (Hb) concentration and haematocrit (Hct) values were decreased. Different blood indices like mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were negatively affected. Level of plasma glucose was elevated whereas protein was decreased. The level of calcium concentration (Ca) was declined in the blood of exposed fish whereas magnesium (Mg) remains unchanged. The activity level of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) was elevated in exposed fish. These effects were more pronounced in the last period of exposure and in higher concentrations. Results of the present study indicate that uranyl acetate has adverse effects on Clarias gariepinus and causes changes in the biochemical and hematological parameters of the fish.     

湛江港区底泥悬浮物对凡纳滨对虾仔虾成活的影响

模拟吹填、疏浚等海上施工过程所产生的底泥悬浮物浓度的变化规律,探讨不同底泥悬浮物浓度下对凡纳滨对虾仔虾成活影响。结果表明:海水中底泥悬浮物浓度超过10mg/L,持续时间超过12h时,将对凡纳滨对虾成活率产生影响,随着悬浮物实验浓度的递加,仔虾的死亡率从13.33%增至96.67%;超过80mg/L,且持续时间超过48h,将对凡纳滨对虾产生严重影响,甚至导致全部仔虾的死亡;悬浮物对凡纳滨对虾的12h、24h、36h和48h半致死量(LC50)分别为54.56、40.29、25.8和19.18mg/L。     

饲料中豆粕含量对军曹鱼幼鱼碳、氮稳定同位素分馏的影响

配制全鱼粉饲料（以鱼粉为蛋白源）、10%豆柏饲料（用豆柏蛋白10%鱼粉）、20%豆柏饲料（用豆柏蛋白20%鱼粉）等3种等氮等能饲料,分别投喂体质量21.34± 1.54g的幼鱼24 d,研究饲料中豆柏蛋白含量对 军曹鱼幼鱼碳、氮稳定同位素分馈的影响。结果表明,随着养殖时间的延长,各饲料组军曹鱼δ13C逐渐上升,δ15N逐渐下降,虽然δ13C和δ15N变化速度上有差异,但除20%豆柏饲料组肌肉的δ15N外,其他各饲料组肌肉和 全鱼在实验结束时均已与饲料达到同位素平衡;军曹鱼肌肉和全鱼的△13^C和△15^N值均随饲料中豆柏蛋白含量 的增加而加大,△13C从4.19‰增加到5.04‰, △15N从0.18‰。增加到 2.20‰,军警鱼金鱼和肌肉的△13C和△15N 相似,但在同位素值变化速度上有差异,因此,在进行生态学营养级研究（长时间尺度）时,肌肉可以代表军警鱼的同位素特征,而在进行生理学研究（短时间尺度）时,肌肉的同位素变化则不能代表军警鱼的同位素变化。     

REDUCED GROWTH IN HYBRID TILAPIA (OREOCHROMIS MOSSAMBICUS×O. NILOTICUS) AT INTERMEDIATE STOCKING DENSITY

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Adverse Effect of TiO_2 Nanoparticles on Antioxidant System and Antitumor Activities of Macroalgae Gracilaria lemaneiformis

Recently, the widespread use of TiO_2 nanoparticles(nano-TiO_2) has attracted the global concern regarding their adverse effects to aquatic organisms. Nanoparticles may get to the aquatic environments and harm the growth of algae. This paper presents the studies of nano-TiO_2 concentrations influence on the photosynthetic characteristics, antioxidant system and antitumor activity of marine macroalgae Gracilaria lemaneiformis after exposed to 0, 5, 10, 20 or 40 mg L-1 of nano-TiO_2. Results showed that the photosynthetic pigment content of G. lemaneiformis obviously decreased and the antioxidant defense system was significantly disturbed after exposure to nano-TiO_2. Compared with control, the maximum level of malondialdehyde showed 3.3-fold increase for 15 days exposure to nano-TiO_2. The activity of superoxide dismutase and catalase enhanced obviously by 1.10-2.24-fold. The aqueous extract of G. lemaneiformis(AEGL) possesses anticancer activity against HepG2 liver cancer cells proliferation and the 48 h-cell inhibition exceeds 35%. But the toxicity of nano-TiO_2 would inhibit the anticancer activity of AEGL. When G. lemaneiformis was exposed to nano-TiO_2, the effect of the aqueous extract of G. lemaneiformis on the cell inhibition, reactive oxygen species production, apoptosis, cycle arrest of HepG2 cells significantly lessened, and which were linearly associated with nano-TiO_2 exposure concentration. Those results further confirmed that nano-TiO_2 can inhibit the anticancer activity of G. lemaneiformis. The results in this work imply that macroalgae can be an effective biomarker of nano-TiO_2 contaminant, and can be useful indicator to evaluate ecological effects of increasing pollutants in marine ecosystem.     

Reduced growth in hybrid tilapia (Oreochromis mossambicus ×O. Niloticus) at intermediate stocking density

Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate stocking density, which can be suppressed by a further increase in density. This project was financially supported by the State Key Laboratory of Freshwater Ecology and Biotechnology of China and by Shanghai Fisheries University (Project SFU. 200003).     

Toxicity of organophosphorus pesticide sumithion on larval stages of stinging catfish <Emphasis Type="Italic">Heteropneustes fossilis</Emphasis>

Sumithion is widely used to control brittle in paddy fields and tiger bug in fish larval rearing ponds. The objective of this study was to elucidate the toxic effects of sumithion on larval stages of stinging catfish Heteropneustes fossilis. Larvae were exposed to two concentrations (150 and 250 μg/L) of sumithion with one control in three replicates of each. Larvae samples were collected at 20- and 24-h intervals followed by observation under a digital microscope. Exposures of stinging catfish larvae to sumithion produced deformities including irregular head shape, lordosis, yolk sac edema, body arcuation, tissue ulceration, etc. The mortality rates of larvae were significantly increased in response to increase in sumithion concentrations. Furthermore, around 30% of the total adult stinging catfish reared in sumithiontreated aquaculture ponds were found to be deformed permanently. These findings highlight that exposure of stinging catfish to sumithion at the critical and sensitive stages in their life cycle may significantly reduce the number of returning adults. Therefore, the use of sumithion for crop protection needs to be considered carefully and alternatives to sumithion should to be developed for controlling aquatic insects in aqua-ponds during larval rearing.     

饥饿和再投喂对尼罗罗非鱼蛋白酶活性的影响

测定了饥饿和再投喂的尼罗罗非鱼胃、肠、肝胰脏蛋白酶活性。结果表明:(1)尼罗罗非鱼蛋白酶的活性以胃为最高,肠为最低,且胃蛋白酶的活性极显著高于肠、肝胰脏(P<0.01),肠和肝胰脏之间差异不显著(P>0.05);(2)饥饿后,蛋白酶活性呈降低的趋势,饥饿处理25d后,胃、肠、肝胰脏的蛋白酶活力分别降低到饥饿处理前的42.7%、41.0%、61.5%,均与对照组差异极显著(P<0.01);(3)再投喂后,饥俄15d以内的鱼蛋白酶活性上升迅速,经过15d恢复投喂,基本上就恢复到了正常水平,且消化酶活性甚至高于一直投喂对照组,而饥饿20、25d的鱼蛋白酶活性虽缓慢上升,但仍无法恢复到正常水平,与对照组差异显著(P<0.05)。     

Effect of Wetland Reclamation on Soil Organic Carbon Stability in Peat Mire Soil Around Xingkai Lake in Northeast China

Content and density of soil organic carbon(SOC) and labile and stable SOC fractions in peat mire soil in wetland, soybean field and rice paddy field reclaimed from the wetland around Xingkai Lake in Northeast China were studied. Studies were designed to investigate the impact of reclamation of wetland for soybean and rice farming on stability of SOC. After reclamation, SOC content and density in the top 0–30 cm soil layer decreased, and SOC content and density in soybean field were higher than that in paddy field. Content and density of labile SOC fractions also decreased, and density of labile SOC fractions and their ratios with SOC in soybean field were lower than that observed in paddy field. In the 0–30 cm soil layer, densities of labile SOC fractions, namely, dissolved organic carbon(DOC), microbial biomass carbon(MBC), readily oxidized carbon(ROC) and readily mineralized carbon(RMC), in both soybean field and paddy field were all found to be lower than those in wetland by 34.00% and 13.83%, 51.74% and 35.13%, 62.24% and 59.00%, and 64.24% and 17.86%, respectively. After reclamation, SOC density of micro-aggregates( 0.25 mm) as a stable SOC fraction and its ratio with SOC in 0–5, 5–10, 10–20 and 20–30 cm soil layers increased. SOC density of micro-aggregates in the 0–30 cm soil layer in soybean field was 50.83% higher than that in paddy field. Due to reclamation, SOC density and labile SOC fraction density decreased, but after reclamation, most SOC was stored in a more complex and stable form. Soybean farming is more friendly for sustainable SOC residence in the soils than rice farming.     

盐度渐变和骤变对褐点石斑鱼存活和摄饵的影响

以人工育苗所得的褐点石斑鱼苗为材料,水温28～31.5℃下,盐度范围0～70以组间距5共设置15个梯度,分别进行盐度渐变和骤变对鱼苗存活和摄饵影响的研究。结果表明:渐变实验中,以5/d升高或者降低盐度时,盐度10～55之间,鱼苗存活率100%;而在盐度降低至5时,平均存活时间为15.16 h,24 h存活率19.1%;盐度降至0,平均存活时间7.92 h,24 h存活率为0,盐度0时其平均存活时间与盐度5时的平均存活时间有极显著差异(P<0.01);盐度60,鱼苗基本不摄食,24 h平均存活时间38.51h,24 h存活率为89.8%,24～48 h存活率为89.8%;盐度65,鱼苗不摄食,平均存活时间10.95 h,24 h存活率0%;盐度65平均存活时间与盐度60之间有极显著差异(P<0.01);鱼苗在盐度25～45间摄食活动活跃。骤变实验中,盐度5～50,鱼苗存活时间>48 h;盐度0,24 h存活率5%,48 h存活率为0;盐度55,24 h存活率100%,24～48 h间存活率83.3%;盐度60,24 h存活率44.1%,48 h存活率降至11.1%;鱼苗在盐度65、70中24 h存活率0%;盐度0、65、70的处理组48 h平均存活时间的显著短于其它各组,盐度0～5、55～70为褐点石斑鱼苗骤变的极限生存盐度。     

高淀粉水平下精氨酸对松浦镜鲤肠道形态与功能的影响

【目的】探讨高淀粉饲料中添加精氨酸对松浦镜鲤(CyprinuscarpioL.)肠道消化酶活性及肠道形态的影响。【方法】选用初始体质量(6.84±0.02)g的松浦镜鲤360尾,随机分为5组,每组4个重复,每个重复18尾鱼。实验饲料分为5组,分别在45%水平的高淀粉饲料中添加质量分数0%、0.6%、1.2%、1.8%、2.4%的精氨酸,实验周期为8周,进行肠道消化酶和形态的测定。【结果】前、中、后肠的淀粉酶活性,各组之间没有显著差异(P> 0.05);添加2.4%精氨酸组的前肠脂肪酶活性显著高于对照组(P <0.05),中肠和后肠的脂肪酶活性各组间没有显著差异(P>0.05);前、中、后肠蛋白酶活性随精氨酸添加量的增加而增加,添加1.8%和2.4%精氨酸组的前肠和中肠蛋白酶活性显著高于对照组(P<0.05),添加2.4%精氨酸组后肠的蛋白酶活性显著高于对照组(P<0.05)。高淀粉饲料中添加Arg显著影响了肠道皱襞高度,但对肠绒毛宽度和肌层厚度没有显著影响。2.4%精氨酸组前肠皱襞高度显著高于其他各组(P <0.05),1.8%精氨酸组中肠和后肠皱襞高度显著高于对照组(P <0.05)。1.2%、1.8%和2.4%组肠体指数显著高于对照组(P <0.05),2.4%精氨酸组肠长指数显著高于对照组(P <0.05)。各组前、中、后肠肠绒毛密度没有显著差异,且排列较整齐。【结论】高淀粉饲料中添加1.8%~2.4%精氨酸可以增加松浦镜鲤肠道消化酶活性,同时改善了松浦镜鲤的肠道形态结构。     

Growth and feed efficiency of juvenile shrimp Litopenaeus vannamei fed formulated diets containing different levels of poultry by-product meal

This feeding trial was conducted to evaluate the potential of poultry by-product meal (PBM) as a protein source in the culture ofLitopenaeus vannamei. Seven isonitrogenous and isoenergetic diets were formulated to near to commercial diet with about 40% protein and 7.5% lipid. Fish meal was replaced by 0, 30%, 40%, 50%, 60%, 70% and 100% of PBM (diets 1-7). The diet with 100% fish meal was used as a control (diet 1). Post-larvae were reared in an indoor semi-closed re-circulating system. Each dietary treatment was tested in 4 replicate tanks (260 L) of 40 shrimp, arranged in a completely randomized design. The shrimps were hand-fed for three times a day to near-satiation (0700, 1200 and 1800) for 60d. Percentage weight gain, survival, feed conversion ratio (FCR), protein efficiency ratio (PER) and body composition of shrimps were measured. There were no significant differences (P>0.05) in growth performance among shrimps fed diets 1-5 (0-60% fish meal replacement). However, shrimps fed diet 7 (100% fish meal replacement) had significantly lower (P<0.05) growth than those fed diets 1-5 (0-60% fish meal replacement). Shrimp fed diets 2-4 (30%-50% fish meal replacement) showed significantly higher growth than those fed diets 6 and 7 (70% and 100% fish meal replacement, respectively). Survival ranged from 94.7% to 100.0% and did not differ significantly (P>0.05) among different experimental diets. No differences in body composition were found among shrimps fed different diets. These results showed that up to 70% of fish meal protein can be replaced by PBM without adversely affecting the growth, survival, FCR, PER and body composition of Litopenaeus vannamei.     

Distribution and expression in vitro and in vivo of DNA vaccine against lymphocystis disease virus in Japanese flounder (Paralichthys olivaceus)

Lymphocystis disease, caused by the lymphocystis disease virus (LCDV), is a significant worldwide problem in fish industry causing substantial economic losses. In this study, we aimed to develop the DNA vaccine against LCDV, using DNA vaccination technology. We evaluated plasmid pEGFP-N2-LCDV1.3 kb as a DNA vaccine candidate. The plasmid DNA was transiently expressed after liposome transfection into the eukaryotic COS 7 cell line. The distribution and expression of the DNA vaccine (pEGFP-N2-LCDV1.3kb) were also analyzed in tissues of the vaccinated Japanese flounder by PCR, RT-PCR and fluorescent microscopy. Results from PCR analysis indicated that the vaccine-containing plasmids were distributed in injected muscle, the muscle opposite the injection site, the hind intestine, gill, spleen, head, kidney and liver, 6 and 25 days after vaccination. The vaccine plasmids disappeared 100 d post-vaccination. Fluorescent microscopy revealed green fluorescence in the injected muscle, the muscle opposite the injection site, the hind intestine, gill, spleen, head, kidney and liver of fish 48 h post-vaccination, green fluorescence did not appear in the control treated tissue. Green fluorescence became weak at 60 days post-vaccination. RT-PCR analysis indicated that the mcp gene was expressed in all tested tissues of vaccinated fish 6–50 days post-vaccination. These results demonstrate that the antigen encoded by the DNA vaccine is distributed and expressed in all of the tissues analyzed in the vaccinated fish. The antigen would therefore potentially initiate a specific immune response. the plasmid DNA was injected into Japanese flounder (Paralichthys olivaceus) intramuscularly and antibodies against LCDV were evaluated. The results indicate that the plasmid encoded DNA vaccine could induce an immune response to LCDV and would therefore offer immune protection against LCD. Further studies are required for the development and application of this promising DNA vaccine.     

Quantitative comparison of the expression of myogenic regulatory factors in flounder (Paralichthys olivaceus)embryos and adult tissues

MyoD,Myf5,and myogenin are myogenic regulatory factors that play important roles during myogenesis.It is thought that MyoD and Myf5 are required for myogenic determination,while myogenin is important for terminal differentiation and lineage maintenance.To better understand the function of myogenic regulatory factors in muscle development of flounder,an important economic fish in Asia,real-time quantitative RT-PCR was used to characterize the expression patterns of MyoD,Myf5, and myogenin at early stages of embryo development,and in different tissues of the adult flounder.The results show that,Myf5 is the first gene to be expressed during the early stages of flounder development, followed by MyoD and myogenin.The expressions of Myf5,MyoD,and myogenin at the early stages have a common characteristic:expression gradually increased to a peak level,and then gradually decreased to an extremely low level.In the adult flounder,the expression of the three genes in muscle is much higher than that in other tissues,indicating that they are important for muscle growth and maintenance of grown fish.During embryonic stages,the expression level of MyoD might serve an important role in the balance between muscle cell differentiation and proliferation.When the MyoD expression is over 30%of its highest level,the muscle cells enter the differentiation stage.     

Effects of Replacing Fishmeal with Animal By-products Meal Supplementation in Diets on the Growth and Nutrient Utilization of Mangrove Red Snapper

A feeding trial was conducted for 75 d to evaluate the nutritive value of a mixture of animal by-products(MAB) as a possible protein source in diets for juvenile mangrove red snapper,Lutjanus argentimaculatus(mean initial body weight,30 g). Fish were fed one of five isonitrogenous diets(40% crude protein) replacing 0,25%(MAB25),50%(MAB50),75%(MAB75) and 100%(MAB100) of fish meal protein with similar percentages of MAB. The MAB consisted of 25% cow liver meal,20% leather meal,20% meat and bone meal,15% blood meal,10% APC(poultry feather meal),8% poultry manure dried,1.5% choline and 0.5% chromic oxide. After 75 d of feeding,fish fed with diets MAB50,MAB75 and MAB100 exhibited significantly lower growth per-formance than that of fish fed with control and MAB25 diets. The optimum level of MAB was estimated to be 23%. Replacement of fish meal by MAB23% showed the following performance:maximum weight gain,510%;SGR,2.39% and FCE,2.83%. The MAB substitution up to 75% of fish meal protein in diets did not show differences in apparent protein digestibility(83.6% for MAB25,79.2% for MAB50,78.7% for MAB75) compared with control(83.4%),whereas in MAB100 group digestibility(65.3%) was sig-nificantly lower than in other groups. The apparent phosphorus absorption of test diet groups was significantly higher(37.1% for MAB25,28.5% for MAB50,55.6% for MAB75 and 54.5% for MAB100) than that of control(11.2%). The levels of protein and ash in the whole body,carcass and viscera increased as MAB substitution in diets increased,whereas lipids and moisture remained con-sistent among all treatment groups. These results showed that approximately 23% of fish meal protein could be replaced by a mixture of animal by-products for juvenile snapper growing from 30 g to 167 g in 75 d without compromising growth performance and feed efficiency.