褶皱臂尾轮虫的高密度培养

本文针对冬季育苗生物饵料缺乏,褶皱臂尾轮虫幼体成活低的问题,采用室内高密度培育轮虫的方法,提高产量.赣榆县广星育苗场,25#～35#池用于轮虫培养,38 m2/池,1#、2#、3#池饵料培育.     

轮虫室内培育实用技术

<正> 褶皱臂尾轮虫(Brachionus plicatilis)具有生长快、繁殖力强,营养丰富等特点,现已成为鱼、虾、蟹类人工育苗不可缺少的优良动物性饵料,且在生产中需求量很大,特别在近几年来的河蟹育苗中,由于育苗时间较早,野生轮虫远远不能满足生产需要。为提高育苗成活率,降低成本,笔者结合省内外轮虫室内高密度培养实践简要总结如下,供育苗同仁参考。 1 培育池     

褶皱臂尾轮虫高密度培育技术的研究

本文在通过实验确认了褶皱臂尾轮虫的最佳培育水温(28～30℃)和比重(1.015)的条件下,开展了轮虫培育水体的紫外线和臭氧消毒处理、不同换水方式、不同的饵料组合和培育方法等试验,以期达到利用小水体实现轮虫生产性的高密度培养,降低劳动成本和生产时间,保证经济水产动物开口活饵料的供应.结果表明:培育轮虫的水体经紫外线和臭氧消毒处理;混合投喂小球藻、面包酵母和光合细菌;经5～7d的培育后,进行全换水等方法有利于轮虫的繁育和持续生长;轮虫初始接种密度为209个/mL,经9d培育,可达到4079个/mL,的高密度.     

海水轮虫培育中的几个技术关键

在鱼类的工厂化育苗中，轮虫作为鱼苗的开口饵料，其数量和质量直接关系到鱼苗的成活率。我国北方地区的牙鲆育苗在冬季进行。由于冬天无法收集到天然的活轮虫，育苗单位都要在塑料大棚中培育轮虫。轮虫培育中的技术关键若掌握不好，常出现败池现象，导致鱼苗缺少开口饵料，直接影响育苗产量，造成生产亏损。笔者根据几年来的实际生产经验，就海水轮虫工厂化培育中的几个重要技术环节作一介绍。     

利用地下卤淡水高密度培育轮虫技术

潍坊市有丰富的地下卤水资源,利用地下卤水进行轮虫人工培育具有得天独厚的条件。笔者在近10年的水产苗种生产中,总结出了一套利用地下卤淡水高密度培育轮虫的生产技术。     

轮虫土池高产培育在虾蟹育苗中的应用

轮虫（褶皱臂尾轮虫）作为一种小型浮游动物，具有广盐广温性、生长繁殖快、培育成本低、营养丰富等优点，是海水鱼、虾蟹育苗中最理想的开口饵料和早期生物饵料。宁波市鄞州区有虾蟹育苗基地2000多亩，以前普遍以蛋黄、豆浆作为开口饵料，这样的苗种质量得不到保证，成活率也较低。近两年来，进行了土池培育轮虫试验，作为虾蟹育苗的开口饵料，取得了较好的经济效益。现将轮虫土池高产培育技术及效益核算总结如下，以供参考。     

海水轮虫工厂化培育中的几个技术环节

在鱼类工厂化育苗中，轮虫作为鱼苗的开口饵料，其数量和质量直接关系到鱼苗的成活率和质量。近几年来，北方地区都在冬季进行牙鲆鱼孵化生产，由于无法收集到天然的活轮虫，育苗单位都在工厂(大棚)进行轮虫培育，一些单位由于没能掌握好轮虫培育中的技术关键，常出现败池现象，导致鱼苗缺少开口饵料，     

菲律宾蛤仔高密度育苗技术

设计和制造了可以大规模应用于菲律宾蛤仔（Ruditapes philippinarum）等经济贝类苗种生产的高密度幼体培育系统、高密度稚贝培养系统,并建立了与之相配套的贝类育苗新工艺。克服了传统育苗方式占地面积大、生产效率低、种苗质量和产量不稳定的弱点,具有低消耗、高质量和高效益的突出特点,是贝类育苗工艺的变革。利用这一育苗技术,可以充分发挥高密度、集约化生产的优势,通过对苗种培育过程中水质、饵料和环境条件的全面控制,消除或减少敌害生物的影响,提高幼体的抗逆能力,从而杜绝抗生素的使用;在降低育苗生产的环境污染同时,向养殖户提供健康、优质的贝类苗种,是一种与环境相协调的、可持续的水产苗种培育模式。     

轮虫规模化培育技术

轮虫作为鱼、虾、蟹等幼体的开口饵料，其适口性，营养价值及饲养效果均优于其他饵料。近年来，由于轮虫规模培育技术的突破，促进了种苗产业的发展与提高。在射阳县沿海地区，河蟹土池生态育苗产业的飞速发展，主要得益于轮虫规模培育技术成熟后满足了蟹苗幼体培育阶段的饵料供应难题。目前轮虫培育产量一般稳定在250kg／667m^2，最高达300kg／667m^2以上，平均产值3000元／667m^2，效益可达2000元／667m^2以上，创造了良好的经济、社会效益。现将射阳县沿海地区轮虫规模化培育技术介绍如下。     

土池培养轮虫与一池多用养殖

<正> 轮虫是鱼、虾、蟹类幼体的优质开口饵料,富含甲壳动物变态蜕皮的激素,能促进其快速生长。在人工育苗生产中,当所培育的苗种幼体从内源性营养向外源性营养转化阶段,轮虫是一种营养丰富的饵料品种。轮虫系小型活体,不污染水质,经技术处理,可     

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.