First identification and characterization of Streptococcus iniae obtained from tilapia (Oreochromis aureus) farmed in Mexico

This is the first study to isolate, identify and characterize Streptococcus iniae as the causative disease agent in two tilapia (Oreochromis aureus) populations. The populations were geographically isolated, of distinct origins, and did not share water sources. Affected fish showed various external (e.g., exophthalmia and cachexia, among others) and internal (e.g., granulomatous septicaemia and interstitial nephritis, among others) signs. All internal organ samples produced pure cultures, two of which (one from each farm, termed S‐1 and S‐2) were subjected to biochemical, PCR and 16S rRNA sequencing (99.5% similarity) analyses, confirming S. iniae identification. The two isolates presented genetic homogeneity regardless of technique (i.e., RAPD, REP‐PCR and ERIC‐PCR analyses). Pathogenic potentials were assessed through intraperitoneal injection challenges in rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio). Rainbow trout mortalities were respectively 40% and 70% at 10⁴ and 10⁶ CFU per fish with the S‐1 isolate, while 100% mortality rates were recorded in zebrafish at 10² and 10⁴ CFU per fish with the S‐2 isolate. The obtained data clearly indicate a relationship between intensified aquaculture activities in Mexico and new disease appearances. Future studies should establish clinical significances for the tilapia industry.     

Significant association of SNP polymorphism in the tilapia enhancer of polycomb homolog 1 gene with salt tolerance

Identifying candidate genes involved into osmoregulation provides a basis for developing molecular markers for breeding of saline tilapia. In this study, we characterized and conducted a functional analysis of the Enhancer of Polycomb Homolog 1 (EPC1) gene in Nile tilapia. The length of the EPC1CDS sequence was 1161 bp, including 14 exons encoding 386 amino acid residues. The expression for EPC1 was investigated in the gill, brain and intestine tissues of Nile tilapia that challenged by 0 ppt, 10 ppt, 15 ppt and 20 ppt of salinity content by qRT‐PCR. We found that the gene was significantly down‐regulated at 20 ppt of high salinity stress. We also detected significant evidence of 5 SNP association in the EPC1 gene with salt tolerance trait by genotyping 192 extreme individuals from a full‐sib tilapia family (N = ~500). The individuals with heterozygous SNP genotypes in the population (with an average survival time of 3,064 s) were significantly less tolerant than the other individuals with the homozygote genotypes (with an average survival time of 5,986 s). Further functional analysis on the EPC1 protein sequences from 31 fish species inhabiting different salinity environments identified seven amino acid sites as significantly associated sites (α < 0.01) with salinity content. These data suggested that the EPC1 gene may be a candidate gene related to osmoregulation process in tilapia. Our findings could contribute to selection of the saline tilapia by using marker‐assisted selection technique.     

Enhanced growth and immuno‐physiological response of Genetically Improved Farmed Tilapia in indoor biofloc units at different stocking densities

An experimental trial was conducted for 90 days to evaluate the growth performance, immunophysiological response of GIFT strain of Tilapia in biofloc‐based rearing system and to assess the relative percentage survival in 3 days after challenging with the virulent strain of Aeromonas hydrophila. Fingerlings with an average body weight 0.98 ± 0.06 g were stocked in triplicate at different stocking densities of 200 (SD1), 250 (SD2), 300 (SD3) and 350 (SD4) m^?3 in biofloc‐based treatments and 150 (C) m^?3 in control (clear water). Biofloc‐based units (SD1 and SD2) obtained significantly better (P < 0.05) growth performances at the end of the experimental period. Mean body weight of fish in biofloc‐based units showed a decreasing trend with increase in stocking density with 100% survival in all units including control. The stress parameters were significantly lower in biofloc‐based rearing units especially in treatments SD1 and SD2 as compared to the control. The fish from the biofloc‐based units (SD1 and SD2) possessed significantly (P < 0.05) higher immune status as compared to control and other biofloc treatments in terms of respiratory burst, serum lysozyme and myeloperoxidase activity. Relative survival percentages were significantly better in biofloc treatments with highest in SD1 and SD2 (83.33%) after challenge study. GIFT strain of Tilapia at higher stocking densities 200–250 nos m^?3 can be taken as optimum stocking density whereas higher stocking densities up to 350 nos m^?3 can be reared in the biofloc systems without compromising the growth and immunity.     

奥尼罗非鱼5种组织中4种同工酶的研究

用聚丙烯酰胺凝胶垂直梯度凝胶电泳法对奥尼罗非鱼肾脏、肝脏、眼睛、肌肉和心脏等5种组织的酯酶(EST)、乳酸脱氢酶(LDH)、苹果酸脱氢酶(MDH)、超氧化物歧化酶(SOD)进行了初步研究,并分析了这4种酶的同工酶位点及酶谱表型。结果表明:奥尼罗非鱼的4种同工酶系统具有明显的组织特异性;EST由7个基因位点编码;LDH酶带多于大多数硬骨鱼典型的5条酶带;MDH和SOD都具有线粒体型和上清液型2种类型。     

Apparent digestibility coefficients of feed ingredients and their prediction in diets for tilapia Oreochromis niloticus×Oreochromis aureus (Teleostei, Cichlidae)

Apparent digestibility of crude protein (CP), lipid, carbohydrate, energy and fatty acids was measured in various feed ingredients fed to hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) including fish and poultry meals, corn gluten, soybean meal, rapeseed meal, sunflower seed meal, wheat, corn, sorghum, barley and wheat bran. Chromic oxide was used as a non‐absorbed marker. A diet compounded from a mixture of these ingredients was then used to examine the possibility of predicting the digestibility of formulated diets. In addition, the effect of pelleting or extrusion on digestibility of a compound diet was examined. Apparent digestibility of CP ranged from 75% to 97%, lipids from 72% to 90% and energy from 39% to 89% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 32% to 80%. Digestibility of fatty acids ranged from 75% to 90% with saturated fatty acids exhibiting digestibilities lower than unsaturated fatty acids. In a full‐fat soy diet containing 19% fat, digestibility of lipids did not decrease. There were no significant differences in digestibility between a diet that was either pelleted or extruded. Tests conducted using a compound diet indicated that ingredient digestibility was additive for protein, lipids carbohydrates and energy. Diets for the hybrid tilapia may thus be formulated on the basis of digestibility of individual ingredients, for the nutrients examined in this study.     

罗非鱼五个品系耐盐性的比较研究

在实验条件下,对罗非鱼五个品系,即吉富品系尼罗罗非鱼、“７８”品系尼罗罗非鱼、奥利亚罗非鱼、尼奥鱼和红罗非鱼的耐盐性进行了比较研究。在９６ｈ半致死盐度（ＭＬＳ－９６）、平均成活时间（ＭＳＴ）及５０％成活时间（ＭＴ５０）三个耐盐指标上,五个品系罗非鱼的耐盐性表现为“奥利亚”＞红罗非鱼＞尼奥鱼＞“吉富”＞“７８”。在盐度为１６‰的咸淡水中,“奥利亚”、红罗非鱼、“吉富”和尼奥鱼的成活率显著高于“７８”,绝对增重率的大小顺序是“吉富”＞红罗非鱼＞“７８”、尼奥鱼＞“奥利亚”。     

四种罗非鱼挥发性成份的GC-MS分析

为了研究四种罗非鱼挥发性成份的化学成分,采用水蒸气蒸馏法提取罗非鱼挥发性成份,用气相色谱-质谱联用仪对其进行分离测定,结合计算机检索对分离的化合物进行结构鉴定,应用色谱峰面积归一化法测定各成分的相对百分含量。结果共鉴定出45种物质:奥利亚和奥尼各26种,尼罗24种,吉富18种。其中,有7种化合物为4种罗非鱼的挥发性成份所共有。2,4-二叔丁基苯酚在挥发性组份中的含量最高(奥利亚38.44%;尼罗37.34%;吉富35.21%;奥尼除外,占14.10%)。在挥发性成份中酯类、醇类、烯烃和有机酸类居多,分别有10种、6种、5种和4种,其中大部分为有特殊香味的挥发性物质,且该类物质在奥利亚、尼罗和奥尼三种罗非鱼中含量较多,在吉富中含量较少。奥尼罗非鱼中还检测出大量的特殊的挥发性物质L-抗坏血酸棕榈酸酯,其含量高达33.64%。     

低分子壳聚糖对罗非鱼的肝脂代谢和饲料利用效率的影响研究

为研究低分子壳聚糖 (SMW Chitosan)对罗非鱼 (Tilapia)肝脏脂肪代谢和饲料利用率的影响效果 ,实验采用单因子浓度梯度法饲养罗非鱼 (体重 1 8 96± 1 2 4g)。 3个月后测定结果表明 ,对照组罗非鱼的肝体比明显高于实验组 ,0 5 0 %低分子壳聚糖实验组罗非鱼的肝体比最小 ;实验组罗非鱼的肝脂含量均显著低于对照组 ,其中含 0 5 0 %低分子壳聚糖组罗非鱼的肝脂含量比对照组下降了2 8 2 4 %;0 5 0 %低分子壳聚糖实验组的饲料系数比对照组下降 2 4 1 0 %。壳聚糖对罗非鱼的特殊增长率也有显著性影响。实验表明 ,一定剂量的低分子壳聚糖能有效促进罗非鱼的肝脂代谢 ,提高罗非鱼的饲料利用能力。     

美国罗非鱼贸易现状及展望

利用近年美国罗非鱼市场信息数据,对美国罗非鱼主要进口国家、进口总量变化、产品种类变化、价格变化等问题进行深入的分析,提出未来罗非鱼市场展望及建议,旨在为中国罗非鱼产业发展提供参考。数据分析表明,中国内地和中国台湾占据美国罗非鱼进口贸易近80%的市场份额,其中以冻全鱼和冻鱼片为主,这2种产品在美国市场将继续处于稳定增长的态势。价格分析结果说明,冻鱼片价格明显高于冻全鱼,但中国内地由于产品质量和品牌问题,产品价格普遍低于同类产品市场平均价,表明中国内地必须进一步加强对罗非鱼产品的质量管理,才能获取更大的利润和市场份额。     

Ontogeny of protease, amylase and lipase in the alimentary tract of hybrid Juvenile tilapia (Oreochromis niloticus × Oreochromis aureus)

Juvenile tilapias (Oreochromis niloticus × O. aureus), with average body weights of groups I, II and III of 55.14, 122.82, and 225.68 g respectively were used to study changes in the activity of protease, amylase, and lipase in different organs and sections of the alimentary tract. Additionally, tract containing digesta, which is closer to physiological conditions, may help reveal the mechanisms of whole chemical digestion process. Another group of tilapias (mean body weight of 111.81 ± 0.14 g) was used to analyze changes in activity of protease, lipase, and amylase in response to varying pH and temperatures. The activity of enzymes in all digestive organs increased when body weight increased from 55 to 122 g, and the activity further increased when the weights increased from 122 to 225 g. The rates of increase in digestive enzyme activity were significantly greater than the rates of growth of the fish. When the activity was compared in different sections of the tract, a similar regularity was found for the three enzymes in all fish. The highest amounts of activity were seen in the foregut and the lowest in the rectum, with the middle amount of activity in the hindgut. The pH ranges for the maximum activity of tilapia protease in the stomach and intestine were 1.6–3.3 and 9.5–10.5 respectively and the optimal temperature in these organs was 55°C. The pH ranges for the maximum amylase activity in the intestine and hepatopancreas were 6–7 and 7.5 respectively, and high amylase activity in these organs was found at 25–35°C. The activity of lipase in the intestine remained unchanged at pH 6.0–9.0 and with temperatures between 25 and 35°C. These results suggest that the ability of tilapia to utilize feed varies at different growth stages and remains relatively stable with changes in environmental pH and temperature, which should be taken into account when designing feed formulas for tilapia.     

罗非鱼内脏中酶的筛选

以罗非鱼内脏为原料,经过酶的提取、活性测定及酶含量计算, 对罗非鱼内脏中的蛋白酶、凝乳酶、脲酶、超氧化物歧化酶、胆碱酯酶、乙酰胆碱酯酶和酸（碱）性磷酸酶进行比较和评价。结果表明：蛋白酶、超氧化物歧化酶、胆碱酯酶和碱性磷酸酶在罗非鱼内脏中含量多、活性高,具有进一步提取研究价值。     

Species-characteristic and subspecies-characteristic haemoglobins in some tilapiine fishes and a comparative study on their globin chains

Haemoglobins of ten tilapia species of the genera Oreochromis, Sarotherodon and Tilapia, three subspecies of the Nile tilapia, O. niloticus, and an artificial hybrid cross were analysed by isoelectric focusing aimed at characterizing the taxonomic value of these oxygen-binding molecules. Heterogeneous haemoglobin phenotypes were observed in haemolysate samples of all the fishes, and species-characteristic as well as subspecies-characteristic patterns could be identified. F1 hybrids were distinguishable from pure parental specimens. Globin chain studies by AU- and AUT-PAGE systems confirmed the heterogeneity and species specificity observed by isoelectric focusing of the tetrameric molecules. A total of eight different -chains and eight different -chains were detected by AU-PAGE and species-characteristic globin chain variants were shown to occur in almost all species. Globin chain profiles of hybrid specimens were characterized by the presence of all parental globin chain variants. © Rapid Science Ltd. 1998     

Potential restaurant markets for farm‐raised tilapia in Nicaragua

Abstract

This study assessed the potential to increase sales of farm‐raised tilapia through domestic restaurants in Nicaragua. Direct personal interviews were conducted with 118 restaurant managers. Information was collected on tilapia and other seafood sales, restaurant and market characteristics, attitudes towards tilapia characteristics, and willingness to add tilapia to the menu. The results from logit analyses suggest that the most promising restaurant markets for tilapia are older restaurants that offered a variety of food and those that served steaks. Larger restaurants that considered tilapia to be a high‐quality product and that offered “ceviche” (fish marinated in lime juice) on the menu were those that tended to sell tilapia. Tilapia farmers and processors in Nicaragua will need to guarantee and ensure the flavor, quality, and safety of their product, and promote these attributes.     

不同罗非鱼品系感染无乳链球菌后对血液和肝胰腺生化指标的影响

为探究无乳链球菌(Streptococcus agalactiae)感染后对罗非鱼的血液和肝胰腺生化指标的影响,本研究以吉富罗非鱼(Oreochromis niloticus)抗病选育系F5代、奥尼罗非鱼(Oreochromis aureus × O. niloticus)、吉富罗非鱼“百桂”品系为对象,通过人工腹腔注射感染无乳链球菌,检测感染后不同时期肝胰腺和血液中的酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、总抗氧化能力(T-AOC)和溶菌酶(LZM)活性的变化。结果显示,奥尼罗非鱼、吉富罗非鱼抗病选育系F5代和吉富罗非鱼“百桂”品系的平均死亡率分别为55.4%、60.5%和78.6%,表明奥尼罗非鱼抗感染能力最强;3个品系感染无乳链球菌后,肝胰腺组织中的ACP、AKP、SOD和T-AOC酶活力均呈先升高后下降的趋势,其中,在感染后24 h,奥尼罗非鱼的AKP和CAT酶活力显著高于吉富罗非鱼抗病选育系F5代和吉富罗非鱼“百桂”品系;而感染后24 h,血清中ACP、AKP、LZM、CAT和T-AOC酶均显著升高,而SOD酶则下降,其中,奥尼罗非鱼的ACP、AKP、CAT和T-AOC酶活性明显高于吉富罗非鱼抗病选育系F5代和吉富罗非鱼”百桂”品系。综合比较6种酶在感染后不同时期的活性变化及3个品系的感染存活率,筛选出AKP和CAT作为评估罗非鱼抗无乳链球菌感染能力强弱的指标。     

纳米材料在罗非鱼养殖中的应用试验

在罗非鱼鱼苗培育池塘和鱼种饵料中应用纳米生物助长器。试验结果表明:池塘放置试验组与对照组相比总产量、成活率、饵料蛋白质效率分别提高15.53%、24.15%、8.95%,饵料系数降低8.25%;饵料放置试验组与对照组相比增重率、饵料蛋白质效率分别提高11.74%、20.67%,饵料系数降低17.12%。并对纳米生物助长器的增产作用进行了分析,提出了在淡水池塘应用纳米生物助长器清洗和晾晒周期的建议。     

Comparative Performance of Four Strains of Nile Tilapia (Oreochromis niloticus) in Brackish Water Ponds in Indonesia

Four selectively bred strains of Nile tilapia (Oreochromis niloticus) were evaluated for production in brackish water ponds in Indonesia. Survival to 124 days was relatively low for all four strains (39%–48%), and growth during the later stages of the trial was poor (SGR < 1.5 %/day) due to water quality deterioration in the pond. Although the ‘Red’ tilapia strain demonstrated the best production parameters, red-colored tilapia bring lower prices in both our test markets (South Sulawesi and Aceh provinces). Of the four strains, the genetically enhanced supermale Indonesian tilapia?×?genetic improvement of farmed tilapia (GESIT×GIFT) cross provided the best economic return.     

发展罗非鱼养殖的优势

罗非鱼（Tilapia）原产于非洲，具有雄性率高、生长快、易繁殖、食性杂、抗逆性强、病害少、群体产量高和肉质鲜美等特点，已成为国际鱼类贸易中的重要品种之一。罗非鱼是联合国粮农组织推荐养殖的优良品种，也是最具产业化发展条件的品种，发展罗非鱼苗种生产有利于提升广西特别是南宁对东盟各国的影响力。目前广西水产研究所罗非鱼良种场为广西最大的优质罗非鱼苗种生产单位，该场年生产供应优质罗非鱼苗种达到8000万尾以上，销往广东、海南、福建、云南、贵州、湖南、湖北、河北等10多个省市，并远销越南和缅甸，客户评价很高，信誉良好。     

Leukocyte response and phagocytic activity in Nile tilapia experimentally infected with <Emphasis Type="Italic">Enterococcus</Emphasis> sp.

This study evaluated the total and differential leukocyte counting and the phagocytic activity in Nile tilapia Oreochromis niloticus experimentally injected with Enterococcus sp. in the swim bladder. Fish were distributed in four treatments in triplicates of non-injected fish, fish injected with 1 ml of sterile saline solution 0.65%, and fish injected with 1 × 10³ and 1 × 10⁶ colony-forming units (CFU) of Enterococcus diluted in 1 ml sterile saline. Twenty-four hours after injection, the fish were anesthetized and the blood collected for white blood cell (WBC) counts, differential counting of WBC, and phagocytic activity of blood leukocytes. The increased numbers of WBC and lymphocytes were followed by decreased number of monocyte after infection. The percentages of phagocytic activities in the blood were 55.3 and 55.9%, respectively, in tilapia injected with 1 × 10³ and 1 × 10⁶ CFU/ml.     

罗非鱼内脏中酶的筛选

以罗非鱼内脏为原料,经过酶的提取、活性测定及酶含量计算,对罗非鱼内脏中的蛋白酶、凝乳酶、脲酶、超氧化物歧化酶、胆碱酯酶、乙酰胆碱酯酶和酸(碱)性磷酸酶进行比较和评价。结果表明:蛋白酶、超氧化物歧化酶、胆碱酯酶和碱性磷酸酶在罗非鱼内脏中含量多、活性高,具有进一步提取研究价值。