淡水鱼养殖中常见疾病的防治措施

鱼类养殖中往往会遇到各种疾病,但是由于鱼类疾病不似畜禽养殖可以看得见、摸得着,所以给养殖者诊断与治疗带来不便,主要描述常见淡水鱼疾病的防治措施,为养殖者提供参考。     

海水养殖鱼类病害防治技术

众所周知 ,生活在天然海域中的鱼类 ,由于环境条件优越 ,密度小、饵料鲜活 ,发生疾病并导致大量死亡的情况非常罕见。但在人工养殖条件下 ,特别是在集约化养殖条件下 ,由于生活环境、鱼体密度、饵料质量等因素都与天然情况差异很大。因此 ,各种疾病也就时常发生 ,并已成为制约养殖生产发展的重要因素。现就海水养殖鱼类病害的防治技术作一简介。1　海水养殖鱼类病害的主要种类1 .1　病毒性疾病目前 ,国内外已报道近 60种来自不同鱼类的病毒或类病毒 ,但多数发现于淡水鱼类 ,海水鱼类仅有 1 0多种。然而 ,其潜在危险却很大 ,从近几年的发病情…     

季节鱼病防治技术

随着水产养殖业高度集约化发展,养殖鱼类面对越来越多的疾病困扰,特别是近几年来水产养殖的鱼类疾病一年四季都在频频发生,给渔业生产带来了严重的经济损失。为了预防和及时治疗各种鱼病,减少养殖生产的经济损失,笔者将不同季节易发生的各种鱼病及预防措施和治疗技术介绍给广大     

季节性鱼病防治技术

随着水产养殖业的高度集约化发展,养殖鱼类面对越来越多的疾病困扰,特别是近几年来鱼类疾病一年四季都在频频发生,给渔业生产带来了严重的经济损失。为了预防和治疗各种鱼病,减少养殖生产的经济损失,笔者将不同季节易发生的各种鱼病及预防措施和治疗方法介绍给广大养殖用户,以供参考。     

斑点叉尾■的细菌病及其防控方法(五)

正鱼类链球菌病是一种在世界范围内流行的疾病,最早的相关报道见于1957年,发生在日本人工养殖的虹鳟中。20世纪80年代以后,世界范围内出现了较广泛的鱼类链球菌感染。鱼类链球菌病最初主要在日本造成危害,目前已在美国、以色列、韩国、西班牙、意大利、澳大利亚、南非等地广泛肆虐,严重危害各种淡水、半咸水和海水养殖鱼类。近几年我国鱼类链球菌感染的报道也呈现增加趋势。病原能够从病死鱼的各种器官组织中分离。与病死鱼     

池塘中几种有害藻类的防治

<正> 在水产养殖生产中,由于环境恶化,病害经常发生。由各种因素引起的鱼类疾病,都会造成养殖产量的大幅度下降,其中尤以各种有害藻类引起的鱼类疾病,对养殖生产者来讲最为棘手。在此,简单介绍几种有害藻类的防治方法。     

鱼类疾病实例剖析与防治

简要介绍鱼类消化道疾病、肝胰脏疾病、脑眼等神经器官病疾的发生机理和实施辨证防治方法,通过对典型病例分析,着重探讨营养缺乏后对鱼类机体的影响及相关疾病,倡导回归自然,实施渔业健康养殖与生态养殖理念及模式。     

走出溶解氧认识误区 为养殖生产保驾护航

溶解氧是鱼类养殖生产的重要水质指标之一,对鱼类生长、水质条件稳定、疾病防治等方面都具有重大影响。长期以来养殖生产者更多的关注缺氧死鱼对养殖生产的影响,对溶解氧不足所造成的潜在危害认识不够,在鱼类出现疾病、生长慢、产量低和养殖成本高时,找不到真正的原因,导致养殖效益受到严重影响。     

甘肃省渔业技术推广总站

正9月份,入秋后甘肃省大部分地区气候凉爽,昼夜温差明显,池塘水温降低,各种养殖病害的危害程度逐渐减弱。预测气温在1 3℃～3 0℃之间,养殖水温在1 2℃～2 5℃之间。此时,池塘载鱼量大,鱼类容易发生缺氧浮头、泛塘等事故,应加强池塘日常管理,做好水质调控,防止因天气突变引起鱼类浮头或泛塘事故发生。本月疾病预防以细菌性疾病和寄生虫病害为主。     

养殖鲤的几种病毒病及其防控方法(上)

正鲤是我国的主要淡水养殖鱼类之一,在养殖过程中经常受到各种病害的困扰,尤其是几种致病性病毒引起的疾病,往往给养殖业造成极其重大的经济损失。现简要介绍养殖鲤的病毒病及其防控方法。一、鲤春病毒血症(SVC)这种疾病由属于弹状病毒的SVC病毒感染引起。在欧洲、俄罗斯、中东、美国及中国等地均有发生。     

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.