农业部"十五"重点推广水产技术项目海水网箱养鱼技术(二)(连载)

海水网箱养鱼的技术复杂吗？总体而言，海水网箱养鱼是一个较为复杂的系统工程。它涉及到养殖种类的选择，苗种培育技术，网箱设施的设计、制作与安装，饲养管理技术，病害防治技术，鱼类的营养，饲料配方的设计，生产与投喂技术，生物饵料的培养与投喂技术等。但对养殖生产者而言，网箱设施、苗种、饲料等物资可直接购买，不必自己设计和生产，只要做好饲养管理工作即可。网箱养鱼技术都有哪些呢？因为网箱养殖的种类较多，不同的种类在养殖技术上有所差异，限于篇幅关系，此处只能以真鲷为例介绍其具体的网箱养殖技术。真鲷都有什么特点呢…     

养鱼网箱设计与安装技术

长期以来,我省网箱养鱼除江口水库的鲢鳙鱼网箱比较成功外,其它多以亏损而告终。究其原因,不仅有养殖品种选择,饲料及投喂技术、病害防治与养殖管理技术等诸多因素,而且网箱的设计与安装技术也是影响养鱼效果的重要因素之一。自1996年我省组织网箱养鱼技术推广协作组,实施《网箱养鱼技术的研究与推广》课题,根据课题分工,笔者负责承担并实施了网箱设计与安装技术的研究,对常规网箱进行了改进,取得明显的效果。现将有关资料整理如下,以备参考。1　网箱的设计与安装技术改进11　网箱规格小型化:常规网箱规格由56—96ｍ3或更大改为16—20ｍ3;…     

小体积网箱养鱼技术

小体积网箱养鱼和目前国内采用的大体积网箱养鱼基本上是大同小异,其不同之处在于小体积网箱箱体小,在网箱中设置了食盘和投饲管,在箱顶加了一     

三峡水库重庆库区船体养鱼

利用船体作为载体从事鱼类养殖起于重庆并发展迅速，１９９８年全市有７５艘养殖船投入生产，养殖船单位养殖面积造价依结构，材料及建造时间介于２５０－８５０元／平方米之间；船体养鱼兼有流水养鱼，网箱养鱼特点，养殖密度及单产高于水库网箱，但因设施折旧费用和江河汛期水情急剧变化导致的鱼类死亡率较高，其产品生产成本略高。     

折叠式网箱

<正> 用丙烯腈丁二烯苯乙烯三聚物(ABS)管子制成框架的折迭式网箱,在任何时间蓄养鱼都是有效的器具。拆散的网箱存放空间小,容易运输,且能很快地装配。该箱是用直径3.8厘米ABS管子和网目9.5毫米网片构成。根据所要求的网箱的尺寸和要蓄养鱼的尺寸,可使用不同直径的管子和不同网目的网片。构成框架的材料为8个弯管,8个T形管(上、下框各4个)和ABS管。构成这样一个网箱,其框架尺寸     

微型网箱养鱼新技术

微型网箱养鱼新技术近年来，养鱼科技户通过生产实践，摸索出一种新的微型网箱高产养鱼模式。它比普通网箱养鱼，投资少，效益大，设施简单，管理方便，最适宜农户家庭养殖。一、网箱结构及设置微型网箱结构尺寸可因水域、水位而定。一般长、宽、高各１ｍ，用聚乙烯或聚丙...     

深水网箱养鱼（Ⅱ）

5深水网箱的主要类型5.1重力式全浮网箱(PEH Cage,Gravity-type cage) 形状见图1。以挪威为代表的重力式全浮网箱,基本都是圆形.以高密度聚乙烯(HDPE)为材料,底圈2-3道250mm直径管,用以网箱的成形和浮力,人可在上面行走。该类型网箱逐渐向大型化发展,现阶段流行的为25-35 m直径,即80-110m周长,最大的周长已达120 m(甚至180 m),深40 m,养鱼200t,最大日投饵量6t。PE50的比重为0.95,可浮于水面,使用寿命在10年以上,据称可达50年。设计性能为抗风能力12级,     

介绍一种近海养鱼张力腿网箱

挪威是世界上近海网箱养鱼最发达的国家之一 ,瑞发 (Ｒｅｆａ)集团公司开发抗风浪网箱发展近海养鱼已有 30多年的历史 ,在挪威最具代表性。他们拥有大型抗风浪网箱养鱼整套技术 ,已开发有柔性圆柱形网箱、钢制工作平台方型网箱和张力腿网箱等类型的近海网箱 ,在挪威沿海从南至北建有 1 0个大型的近海网箱养鱼基地 ,在意大利、丹麦、俄罗斯、印度、缅甸、中国等国家都建有他们的近海网箱养鱼基地。瑞发公司近海网箱养鱼的产业化程度高 ,它不仅拥有近海网箱生产的整套设备 (含网线生产、网衣编制、防污损处理、网箱加工及附属设备生产、海上工…     

小网箱养鱼技术

1　小网箱养鱼技术的引进和推广小网箱养鱼技术 ,就是小体积高密度网箱养鱼技术 ,是 1 991年由美国传入我国的。1 994年夏 ,美国奥本大学水产养殖专家史密脱博士来我省举办了首期小网箱养鱼技术培训班 ,此后该项技术逐步在我省推广 ,黄山、安庆、马鞍山、合肥、蚌埠、淮南、六安等市地都有一定的养殖规模 ,据不完全统计 ,1 999年全省推广养殖达 1 5万立方米。2　小网箱养鱼的特点及优越性小网箱养鱼与传统的网箱养鱼主要的区别在于 :一是体积小 ,传统网箱一般面积数十平方米 ,深 2米左右 ,体积几十到一、二百立方米 ,而小网箱通常为 1— 4…     

安化县千只网箱下资江

1991年曾有一口节粮型网箱产鱼超双吨,打破全省纪录的安化县,1992年网箱养鱼又有新发展。据统计,全县网箱养鱼规模已由1991年的47村、315户、489只扩大到1992年的96个村、615户、1205只,新增网箱716只,增长了1.5倍;还有已落实好的育种网箱300只,准备在6月份安装下水,年养鱼网箱总数可突破1500只。县委、县政府已将网箱养鱼列入调整产业结构,建设高效农业的重要内容,采取了4条支持和服务措施: 一是切实加强领导。县政府将网箱养鱼列入全县八大农业开发工程的重要项     

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.     

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.     

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.