文蛤室内人工育苗技术

文蛤（Merertrix merctrix Linnaeus）为蛤中上品，肉味清鲜，俗称天下第一鲜，深受国内外消费者喜爱。文蛤多分布在较平坦的沙质海滩中，含沙率50％～90％，以60％-80％为最好。幼贝多分布在高潮区下部，随着生长逐渐向中低潮区移动，成贝分布于中潮区下部，直至低潮线以下水深5～6米处。为解决本地区文蛤苗种短缺的问题，我们进行了文蛤室内人工育苗技术试验，现将试验情况介绍如下.     

文蛤养殖实用技术

文蛤是一种经济价值较高的海产贝类，其肉嫩味鲜，营养丰富，为蛤中上品，享有“天下第一鲜”的盛誉，是我国大宗出口的鲜活水产品之一。随着我国加入WTO及国家《无公害农产品管理办法》的颁布，文蛤等海产贝类在我国水产品出口中的比例将不断提高。因此，文蛤养殖发展前景喜人。现将该品种养殖技术介绍如下：一、养殖场选址文蛤具有随着生长而逐渐向低潮区或潮下带浅水区移动的习性，表现出个体大小不同、分布潮区不同的特点。养殖潮区太高，干露时间长，索饵时间短，生长就慢；中下潮区和低潮区干露时间短，索饵时间长，生长比较快。因…     

放苗密度对文蛤生长的影响

在自然状态下,水质、底质等自然条件对文蛤生长有着较大的影响,对于人工移植苗种进行养殖生产,放苗密度是影响文蛤生长的重要因素。本文通过两组不同密度的试验,初步探讨了在滩涂上不同的放苗密度对文蛤生长的影响。 试验方法: 试验在自然贝场进行,滩涂底质为细沙,涨潮流速0.5—1.5小节,试验分两组,中潮区为A组,大潮于露4—5小时;低潮区为B组,大潮干露2小时左右。每组设3个相同的试验面,3种不同的放苗密度。试验面由铁丝电焊筛网围成封闭“笼状”网箱,筛网     

渤海湾大口河潮间带文蛤网围养殖试验

1　试验区条件文蛤网围养殖的场地选择 ,是根据文蛤生活习性 ,应在风浪较小、潮流畅通平缓、水质肥沃、滩涂平坦、水质无污染、含沙量在 70 %以上的潮间带中潮区和低潮区进行文蛤网围养殖。试验区选择在我市旺子岛附近的潮间带的中潮区下部 ,进行文蛤网围养殖试验 ,此处属于不正规半日潮 ,春、夏季白天大潮、夜间潮小 ,而秋冬则相反 ,如果把试验区选择于低潮区 ,则秋季不易管理。经过权衡利弊 ,最后定于中潮区下部 ,底质适宜且平坦 ,而适予文蛤网围养殖 ,离海岸约 2 5 0 0 m,此处属于渤海湾南岸。2　试验步骤与方法2 .1　试验区的修建试验区…     

划区管理 文蛤丰收

锦县有十万多亩滩涂,其中七万亩可生长贝类,现有五万多亩生长着大量白蚶子(四角蛤蜊)、文蛤和麻蚶子等,资源蕴藏量约有10万吨左右。过去,锦县文蛤的地理分布向来是面广而稀,又在低潮区,不易采捕,常年产量均在50—300吨左右,所以没有得到应有的重视。自从1965年交给附近社队管养后,实行了划区管理,移植苗种、圈养亲贝等增殖措施,并采     

文蛤增养殖技术讲座──第三讲 海区文蛤养殖技术

海区文蛤养殖具有成本低、产量高、见效快、收益大等优点。海区文蛤养殖技术归纳起来有海区文蛤护养技术和海区文蛤围网精养技术。1养殖场地的选择1．1潮位文蛤喜底栖在潮流畅通的中潮区或低潮区。为便于管理，海区文蛤养殖场地一般设在中潮区下部至低潮区中部比较适宜，这主要有三方面优点：一是这一区域潮流畅通，饵料生物丰富；二是采捕时间长，便于作业；三是夏秋季节退潮露滩时间适中。如设在低潮区下部，虽然文蛤的摄食时间长，生活环境相对稳定，夏秋季节不会遭到曝晒而死亡，但退潮露滩时间短，不便于生产管理和来捕收获。1·2底质…     

浅谈围塘文蛤养殖的几个问题

文蛤，属于软体动物门、瓣鳃纲、真瓣鳃目、帘蛤科。贝壳近于心脏形，表面平滑。文蛤多分布在较平坦的砂质海滩中。幼贝多分布于高潮区下部，成贝分布于中潮区下部、至低潮线以下水深５－６米处。文蛤为广温性半咸水贝类，最适水温在１５－２５℃，适应海水比重在１．０１４０－１．０２４０，地理分布较广。文蛤具有随着生长由中潮区向低潮区下带移动的习性，俗称“跑流”。 文蛤为高经济价值贝类，我县规模开发也只有近两年。１９９９年４月份引进北方文蛤７２００公斤，规格为１６０颗／公斤，分别放入５口海水围塘（总面积为１５．３公…     

文蛤的养殖技术之一潮间带文蛤网围养殖技术的研究

文蛤网围养殖的场地选择是根据文蛤生活习性，在风浪较小，潮流畅通平缓，水质肥沃无污染，滩涂平坦，含沙量在７０％以上的潮间带中，低潮区进行。本试验选择在山东省滨州市旺子岛附近的潮间带的中潮区下部进行文蛤网围养殖试验。此处属于不正规半日潮，春、夏季白天大潮，夜间潮小，而秋、冬季则相反。如果把试验区选择于低潮区，则秋季不易管理。经过权衡利弊，最后定于中潮区下部，底质适宜且平坦，离海岸约２５００ｍ，处于渤海湾南岸，适宜文蛤网围养殖。一、试验材料与方法。１．试验区的修建。试验区四周使用木桩和网片全部围拦起来…     

浅海筏式吊养文蛤初步试验

文蛤具有迁移习性，滩涂围栏养殖管理不便。为此，进行了筏式吊养初步试验。5月开始投放壳长2．5—3．0cm文蛤苗种2500kg，至10月10日收获壳长4cm以上文蛤7200kg，平均每笼纯收人17．6元，文蛤长势良好。对影响存活率的因素以及放养密度、苗种选择进行了探讨。     

文蛤池塘养殖技术

文蛤(Meretrixmeretrix)营养丰富,肉味鲜美,有天下第一鲜的美誉,是我国滩涂养殖的传统品种之一。丹东地区20世纪90年代开始进行文蛤池塘养殖试验,并取得成功,得以迅速推广。现介绍如下。1　文蛤养殖池塘的选择1 1　位置　选择位于中低潮区,风浪较小,底质为细沙质或泥沙质的     

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).     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

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.