杂交条纹鲈生物学特性及池塘苗种培育技术

苗杂交条纹鲈是由雌性条纹鲈与雄性白鲈杂交而成，这种杂交称为“原型杂交”，此杂交种产生的初期被称为“棕榈鲈”。近年来通过雌性白鲈与雄性条纹鲈杂交产生了新的杂交种，称此种为“阳光鲈”。目前，杂交条纹鲈在美国游钓领域已被广泛接受。近几年，我国台湾、内陆等地区已引进了杂交条纹鲈，养殖效果很好。一、生物学特性１．外部形态杂交条纹鲈的外形特征介于其双亲之间。体形侧扁，体侧具条纹，胸鳍和侧线下半部的条纹断断续续。具有两个背鳍，第一背鳍具８～９根硬棘，紧连其后的第二背鳍具１根硬棘和１３～１４根鳍条。尾鳍叉形，分…     

海鱼淡养新品种——杂交条纹鲈

杂交条纹鲈是由雄性白鲈与雌性条纹鲈杂交的子一代，具有显著的杂种生长优势：生长快、个体大、产量高、抗病力强、肉质非常鲜美。该鱼是广盐性鱼类，既适于在淡水池塘里饲养．也适于在沿海地区的半咸水池塘里养殖。杂交条纹鲈的外形特征介于它的双亲之间，体略侧偏．被覆鳞片．体     

杂交条纹鲈

杂交条纹鲈于 1993年由广东省引进养殖。经试养表明，杂交条纹鲈与我国现有鲈科养殖品种相比，具有体型和体色好看，肉质好而有特殊香味，商品价值高等优点，是很有发展前途的养殖品种。目前在广东、福建等地已有小规模养殖，其他省市也纷纷引种试养。笔者根据多年来从事杂交条纹鲈养殖和繁殖方面的实践体会，简要介绍如下。 　　一、生物学特性 　　1.形态特征 条纹鲈体侧扁，呈纺锤形。鳞片呈银白色，比其它鲈鱼大。整个体色除背部的小部分呈青灰色外，体侧和腹部都呈银白色，侧线上下都有纵向排列的黑色条纹。纯种条纹鲈体型较长，体长与…     

杂交条纹鲈的生物学特性及养殖技术

条纹鲈又称条纹石鳍，原产于美国东海岸，是一种大型的肉食性鱼类，利用条纹鲈(♀)与白鲈(♂)杂交，产生的子一代为杂交条纹鲈，杂交条纹鲈与其亲本相比具有个体大、生长快、抗病力强、成活率高等优势，因而生产上把杂交条纹鲈作为主要的养殖对象。我们于1998年进行了杂交条纹鲈的一系列养殖及繁殖方面的探索，试验表明，杂交条纹鲈与我国现有鲈科养殖品种相比，具有外观美、肉质好，     

杂交条纹鲈的生物学与养殖技术

１分布与特征杂交条纹鲈是由条纹鲈（Ｍｏｒｏｎｓａｘａｔｉｌｉｓ）与白鲈（Ｍ．ｃｈｒｙｓｏｐｓ）杂交而成。条纹鲈为降河洄游鱼类，主要分布于新西兰斯到弗罗里达的大西洋沿岸及弗罗里达到得克萨斯的墨西哥湾，１９世纪９０年代初期被移植到美国的西海岸，现已形成自...     

美国杂交条纹鲈苗种培育水体理化因子调控和生态条件初探

进行了美国杂交条纹鲈的苗种培育试验，科学调节池塘水体理化因子，初步探讨了美国杂交条纹鲈生长的适宜生态条件。认为美国杂交条纹鲈适温范围广，苗种培育过程中溶解氧应在4mg/L以上，碱度、硬度保持3me/L左右，pH8．0以上，COD应在10mg／L以下，对氮、磷营养元素和苗种培育饵料生物也进行了分析。     

杂交条纹鲈繁殖技术

杂交条纹鲈是由条纹鲈(Ｍｏｒｏｎｓａｘａｔｉｌｉｓ)与白鲈(Ｍ、Ｃｈｒｙｓｏｐｓ)杂交而成,其形态介于两个亲本之间。杂交条纹鲈能生活于溪流、大型水库、湖泊以及池塘,主要生活在自然水域的中上层。杂交条纹鲈适应性强,适温范围4～33℃,最适生长范围25～27℃。适宜盐度0～25‰,可耐的最高盐度35‰,在海水、淡水中均能生活。杂交条纹鲈可自然繁殖,繁殖水温为15～20℃,在池塘人工饲养条件下,性腺可发育至成熟,但不能在池塘中自然繁殖,也未见人工繁殖的详细报道。杂交条纹鲈为一垂钓、食用的名贵鱼类,为掌握杂交条纹鲈的繁殖技术,作者于199…     

水产养殖新品种—条纹鲈

条纹鲈(Morone saxatilis)，俗称线鲈、淡水石斑，因其体侧的平行横纹而得名。另一种为雌性条纹鲈和雄性白鲈(Morone chrysops)的杂交子代，称为杂交条纹鲈。其成长比两亲代迅速，对环境条件的适应能力更强，养殖时成活率高，具有杂交优势。     

银鲈胚胎和仔、稚鱼发育观察

实验对银鲈受精卵的胚胎及仔、稚鱼发育进行连续跟踪观察,结果表明:银鲈受精卵具有在淡水鱼类中比较少见的油球,水温25.4～27.8℃条件下,24小时胚胎破膜而出.出膜仔鱼3日龄开始平游,消化道形成,已能开口摄食;35日龄全长2.3～3.0cm,全身已布满鳞片,形态已具备成鱼特征.     

杂交条纹鲈苗种与成鱼养殖技术

条纹鲈原产于美国,因其体侧有沿身体纵向排列的7道￣8道条纹而得名,杂交条纹鲈为条纹鲈与白鲈的杂交子一代。美国将杂交条纹鲈作为主养对象,养殖产量在淡水品种中排于斑点叉尾鮰之后居第二位。杂交条纹鲈因其具有显著的杂交优势:生长速度快、个体大、抗病力强,目前己成为世界性     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.