日本对虾亲虾越冬及性腺促熟技术研究

利用当地养殖的日本对虾作亲虾，进行了越冬增减和性腺促熟技术研究。从入池越冬水温１３℃开始，每天升温０．５℃，至２０－２３℃时，恒温２天，对２４℃停止升温，取出交尾雌虾放入温水池，每天按０．５℃升温至２６℃待产。性腺发育快，产卵效果好。用镊烫法处理雌虾眼柄，比未处理眼柄的亲虾能提前７天产卵。处理过的亲虾死亡率为３．６２％，结果：４９７尾越冬亲虾产下６９８０万粒受精卵，孵化率平均为７７．０８％。     

海湾扇贝亲贝室内越冬及育苗试验

利用冬季闲置以虾育苗池进行海湾扇贝亲贝室内越冬，提高了亲贝质量，缩短了促熟时间，越冬成活率，性腺指数，孵化率分别达９６．２％，８．１％和５０％分别比海上越冬提高了７４．９％，３５％和３００％。专家鉴定认为，本研究属国内首创。     

利用温泉水越冬罗氏沼虾试验

本试验利用温泉水，在土池塘越冬罗氏沼虾，历经１９７天，平均水温２１．７℃，水质状况，一般溶解氧４ｍｇ／ｌ，ＰＨ７￣８，氨氮０．５ｍｇ／ｌ，透明度３０￣４０ｃｍ。经常投饵，越冬期平均尾日增重０．０６ｇ，性腺发育正常，成活率达６６．６％，试验获得初步成功。     

假睛东方豚对维生素C和E的需求试验

在假睛东方豚越冬期间，通过６８天试验表明，在饵料中添加维生素Ｃ和Ｅ对假睛东方豚的生长发育有明显影响，平均日增重０．７６ｇ，比未加维生纱Ｃ和Ｅ之前提高８．５倍，日均死亡率降低５１％，维生素Ｃ和Ｅ的添加量分别占饵料的３￣５‰和１￣２‰为宜，投喂后２￣３周见效。     

日本囊对虾亲虾人工繁育技术初步研究

2003年11月18日～2004年6月18日期间，采用人工养殖的日本囊对虾，经过越冬培养和室外培育（性腺促熟、交尾），人工控制光线、饵料、温度和培育密度等手段，亲虾性腺均可发育成熟。在越冬培养中光线为500～800lx之间、温度为9～10℃、饵料为沙蚕及杂色蛤，亲虾培育密度为12～30尾／m^2，越冬实验结果，亲虾体重增长率为10．9％，存活率为93．2％。在室外培育中温度为13．6℃、养殖密度为1．3尾／m^2，饵料以蜾赢蜚、藻钩虾和低值贝类为主。实验结果，亲虾体重增长率为5．1％、存活率为90．5％、交尾率为100％。2004年6月24日～7月10日利用人工繁育的日本囊对虾亲虾进行苗种生产实验。实验结果，每尾亲虾产卵量为20～25万粒／尾、孵化率为82．96％、出苗率为62．8％。实验表明，人工繁育的日本囊对虾亲虾可用于正常的苗种生产。     

罗氏沼虾越冬及亲虾培育技术

通过采取一系列严格的措施措施，提高罗氏沼虾越冬成活率及亲虾抱卵量，从而提高产苗量，平均每立方水体产苗量达到７万尾以上，显著高于一般３－５万尾的水平。其主要技术措施是：严格筛选越冬亲虾，合理放差，适时升温，严格控温以及后期通过增喂螺肉，蛏肉等鲜活饲料进行强化培育，促进亲虾性腺发育，增加抱卵次数。     

提高温室亲鳖产卵效果研究

采取塑膜大棚采光保温、锅炉增温及其它措施，使４２０ｍ＾２池水温度保持在２８￣３２℃。亲鳖自１９９５年１月１０日￣１０月１１日，共产卵１８１１穴，２８３３２枚，受精率９４．５％，平均每只雌鳖产卵５．１２穴，８０．０３枚，比常温条件下平均增加产卵３．６穴，６４．８５枚，受精率提高９￥，产卵期延长１５０天。     

盐度对九孔鲍摄食_生长及存活的影响

九孔鲍摄食人工饲料的盐度范围为２０￣３８,其中较适宜的盐度范围为２５￣３５,在此盐度范围内,小规格鲍（平均壳长１．３０ｃｍ,平均体重０．３７ｇ）的壳长日增长为９１．５￣１０２．３μｍ,日增重为８．６０￣１２．５５ｍｇ;大规格鲍（平均壳长２．７ｃｍ,平均体重２．３ｇ）的壳长日增长为５６．３０￣８１．８０μｍ,日增重为１２．６８￣２２．４８ｍｇ,其最适生长的盐度为３０￣３５,存活率为９７％￣１００％。     

环渤海地区长江蟹抱卵越冬问题与对策

近几年，长江蟹北称环渤海沿岸，抱卵越冬后作亲蟹，春天再大批量返供苗种，有力地促进了长江流域河蟹养殖业的发展。对在抱卵及越冬中发现的问题，我们进行了初步探究，并采取了积极对策，确保了亲蟹抱卵质量，提高了越冬成活率。１问题１．１滞后发育 生产中对比发现，在同样的培育条件下，长江蟹与当地河蟹相比，性腺或胚胎发育要滞后１０－１５天。１．２卵色异常与卵子退化 抱卵越冬中或在入室培育时发现，约有３．５％的抱卵蟹，其卵子为桔红色或桔黄色，并在培育中渐渐退化，镜检根本看不到正常发育的胚胎，不久，整个卵块变为粘团状…     

异育银鲫性别控制的研究

用含４００和８００ｐｐｍ １７α－甲基睾酮的饲料投饲孵化后３天的异主能银鲫仔鱼４５天，再用无激素的饲料饲养成年，结果获得了一批性腺呈细线状、难辨雌雄的中性不育鱼。经随机解剖测定，中性不育鱼的比例分别是对照组的３．７１和３．４０倍；与对照组比较，试验组的平均体重分别增长１６％和１１％，平均性腺系数分别降低４５．５％和２４．５％；平均出肉率分别增长６．５％和５．０％。切片观察未发现中性鱼的性腺内有生殖     

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.