高白鲑仔鱼饲育

为解决高白鲑仔鱼饲育期与室外鱼池放养期不同步的矛盾，采取室内流水，集约化饲育方式，利用活饵料与人工配合饲料投喂。在透明度较高的涌泉水中，水温8－13℃，溶解氧8－10毫克／升，水交换量为14－16升／分的条件下，以每平方米放养6000尾的密度，并采取综合管理技术，经30天的饲育，其每日可增长0．3毫米，增重0．66毫克，其绝对增长量由3．5毫克平均增长至18．51毫克，全长由9．7毫米增长至18．4毫米，成活率可达73．78％－82．91％。     

残饵及代谢物对斑节对虾育苗的影响

试验对象为平均体重0.57毫克、全长6.5毫米的斑节对虾后期幼体,放养在充气的海水水族箱内,密度为每升20尾,试验用的饲料为碎虾肉,各试验组的投饲量分别为10毫克/升、50毫克/升、100毫克、250毫克/升和500毫克/升,并设一水族箱投喂硅藻作对照。试验结果表明:投饲量为10毫克/升、50毫克/升、100毫克/的试验组,后期幼体的增重率接近,且都比对照组高一倍左右;最低投饲量试验组的成活率较好,与对照组比较无显著差异(P>0.05);其它试验组的成活率随投饲量增加而下降;投饲量为50毫克/升时,仔虾的成活及生长均可,超出这个投饲量,水体中有机物和代谢物积累加快,溶氧量下降,水质迅速恶化。     

苏州澄湖渔业资源调查及综合开发思路

2001年3月-12月。对澄湖的水质理化因子，水生生物等方面进行调查。结果为：pH值7.3-7.7，透明度0.3-0.8米，溶氧7.2-10.2毫克/升，COD13.3-17.3毫克/升，氨态氮0.5-1.3毫克/升，总磷0.090-0.156毫克/升，酚0.001-0.004毫克/升；浮游植物7门72属，生物量12.7331毫克/升；浮游动物63属91种，生物量3.27毫克/升；底栖动物（软体动物）73.6179克/米^2。澄湖属天然中-富营养型湖泊，适宜采取调整品种结构，保护和开发优质野生鱼类资源，走合理开发，可持续发展经营之路。     

一冬龄尼罗鱼与家鱼混养的经济效果

为了提高尼罗罗非鱼(以下简称尼罗鱼)商品规格和养殖尼罗鱼的经济效益,我们进行了一冬龄尼罗鱼与家鱼混养的试验,现将1983年试验结果报告如下:一、材料和方法1.试验池条件。试验池6口,总面积117.2亩,水深2～2.5米。7、8、9三个月分别对各池水的主要理化因子和浮游生物量进行测定,测得的平均值为:水温24～33.5℃,pH6.5～7.2,溶解氧1.4～14.7毫克/升,有机物耗氧量11.99～16.79毫克/升,浮游植物量473.7～2,331.4万个/升,浮游动物量15.3～35.1万个/升。2.试验鱼来源及放养情况。尼罗鱼种由本场越冬温室提供,规格为5～15克,先后于4月30日、5月     

高关水库浮游生物现存量及鲢,鳙鱼产潜力的研究

根据1985年3—11月采样测定结果,高关水库浮游植物生物量平均密度为125.3万个/升,生物量为1.9208毫克/升;浮游动物平均密度为4012个/升,生物量为4.80毫克/升。根据浮游生物现存量估算鲢、鳙鱼产潜力为25万公斤,其中鲢5.8万公斤,鳙19.2万公斤。本文还对高关水库鲢、鳙的合理放养问题进行了探讨。     

JZ-虾蟹型清塘剂简介

本品属双烷基二甲基卤类复合制剂 ,其特性在规定浓度范围内起到高效、速效杀灭野杂鱼、细菌、病毒、寄生虫卵及藻类而却能维持虾、蟹存活的作用。现简介如下 :1　清塘灭鱼作用　作者在 6口平均水面 2 0平方米、水深 1米的水泥池中放养草、鲢、鳙、鳊、鲤、鲫、罗非鱼、罗汉鱼、鱼、鱼参鱼、及虾虎鱼等品种 ,应用本剂分别使池水成 5、 6、 7、 8、10毫克 /升浓度及设对照池比较。这些池水水质ｐＨ7 5～ 8 2 ,硬度 3 8毫克 /升 ,溶解氧 >4毫克 /升 ,水温 2 0～ 2 2℃。经观察 4 8小时的结果表明 :鲢、鳙、鳊、罗非鱼、鱼参鱼、罗汉鱼及…     

农药杀虫双对鱼类毒性的研究

由实验得出杀虫双对鲤鱼、白鲢96小时半致死浓度分别为4.7毫克/升、4.51毫克/升,而安全浓度则分别为0.47毫克/升,0.451毫克/升;对草鱼胚胎最大无作用浓度为1.0毫克/升,对大型水蚤96小时半致死浓度为0.13毫克/升。综合评价杀虫双的毒性,0.13毫克/升浓度对鱼类生长、鱼卵胚胎发育,以及饵料生物均无急性毒性作用,以此浓度乘0.1(应用系数)得0.013毫克/升,故建议渔业水体杀虫双浓度以不超过0.013毫克/升为宜。     

3种不同斑点叉尾(鮰)养殖模式的水质比较分析(下)

4.高锰酸钾指数监测期间,1^#塘的高锰酸钾指数最高值为16.02毫克/升,最低值为6.11毫克/升,均值为(11.68±1.19)毫克/升;2^#塘的高锰酸钾指数范围6.45~13.70毫克/升,均值为(10.93±0.94)毫克/升;5^#塘的高锰酸钾指数介于6.15~10.20毫克/升,均值为(8.33±1.79)毫克/升。水体中的高锰酸钾指数呈逐渐升高态势(图4)。     

采取措施恢复太湖大中型经济鱼类资源

太湖是我国第三大淡水湖泊,湖底平坦,平均水深2.27米,年平均水温17.28℃,降雨量1,000毫米以上,水质基本良好。湖区饵料生物丰富,浮游植物年平均生物量为4.85毫克/升,浮游动物为4.77毫克/升,底栖生物的现存量平均是4.8克/米~2,是鱼类生长的良好场所。     

热带观赏鱼的疾病预防

北方地区热带观赏鱼的养殖主要以工厂化养殖为主,在疾病预防上应从鱼体本身、养殖水体及病原体三者之间的相互关系入手,采取四消四定的预防措施,如果切实做到预防,能够有效地控制鱼病的发生。1.鱼池、养殖水体消毒鱼类放养前对水泥池进行消毒,具体用10～50毫克/升漂白粉或100毫     

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.