单环刺螠对水温、盐度和pH的耐受性的研究

以单环刺螠幼螠为材料测定其生活环境的部分水质指标。单环刺螠幼螠生存,水温超过31.6℃会导致幼螠死亡,且降温后幼螠不能恢复;幼螠生存的盐度为13.8~35.9,适宜盐度20.8~35.2;幼螠生存的pH为4.0~10.5,适宜pH 5.96~9.01。盘锦地区近岸沿海和海水养殖池塘可以进行单环刺螠的养殖,水质因子可以满足其正常生长发育。     

珍珠龙胆石斑鱼对水温、盐度和溶解氧的耐受研究

为研究珍珠龙胆石斑鱼对海水温度、盐度、溶解氧等主要环境因子的耐受,选择健康活泼的珍珠龙胆石斑鱼个体,采用渐变式方法达到设计的要求,进行试验。结果表明:珍珠龙胆石斑鱼对水温、盐度和溶解氧耐受范围较广,适宜水温为20～35℃,临界下限水温为10℃,临界上限水温为39℃;适宜盐度为11～40,临界下限盐度为3,上限盐度可到45以上;耐受低氧:DO₁为0.70 mg/L,DO₅₀为0.67 mg/L,DO₁₀₀为0.60 mg/L。     

莫桑比克鳗鲡对温度、盐度和pH的耐受性试验

就莫桑比克鳗鲡对水温、盐度和pH的耐受性进行了初步研究.试验结果表明,适宜水温为12.0～35.0℃,临界上限为40.0℃.临界下限为0℃;适宜盐度为0～15.临界极限为45;适宜pH为4.0～9.5,临界上限为11.0,临界下限为2.5.     

嘉庚蛸对温度、盐度的耐受性试验

2003年4～10月在试验条件下研究了嘉庚蛸成体对温度、盐度等环境因子的耐受能力。利用温水和冰水调节水温，在温控加热器和生物冰袋的协助下完成温度耐受性试验；通过淡水和海水晶调节试验过程中所需的盐度变化。试验结果表明：嘉庚蛸的适宜温度范围为12．0℃～31．0℃，临界上限水温为35．2℃，临界下限水温为0．5℃；耐受盐度的范围比较广泛，为4．8～48．5，适宜养殖的盐度为18．4～33．1。较高的耐受性范围可以保证嘉庚蛸更好地适应其生存的环境，不至于由于环境因子的激变造成嘉庚蛸的大规模死亡。因此，人工养殖和育苗过程中，保持环境因子的稳定是获得高孵化率的先决条件。     

水温和盐度对黄姑鱼受精卵孵化的影响

黄姑鱼（Nibea albiflora Richardson）是具海水养殖潜力的高价值经济鱼类。本文研究了不同水温（14~32 ℃）和盐度（5~45）条件下,黄姑鱼受精卵的孵化状况。水温低于17 ℃和高于32 ℃时不能孵化;盐度低于15和高于50时也不能孵化。在海水盐度25时,孵化的适宜水温为20~29 ℃,最佳水温为20~23 ℃;在水温22±0.5 ℃时,黄姑鱼孵化的适宜盐度为25~40,最佳盐度为25。通过均匀设计,分析水温（X1）和盐度（X2）对孵化率（Y）的综合影响,获得最佳回归模型为Y=254-4.52 X1-2.78 X2（R2＝0.8808）,水温和盐度对回归的贡献率分别为64.8%和55.1%,预测最佳的孵化条件为水温20 ℃、盐度24。     

卵形鲳鲹人工养殖试验

卵形鲳鯵是新开发的的海水养殖经济鱼类,本试验利用海水网箱及土池进行养殖,投喂配合饲料,叉长4~5 cm的种苗,在水温18℃~32℃、盐度15~31、pH值7.8~8.1的养殖条件下,经4~5个月养殖,体重可达400~600g,当年达到商品规格。     

黑斑口虾蛄对水温、盐度和pH的耐受性研究

为研究黑斑口虾蛄对海水盐度、水温、酸碱度(pH)等主要环境因子的耐受性,选取无伤病、活力强,体长(10.0±0.5)cm的虾蛄个体,采用渐变式方法达到设计的要求,进行试验观测。试验结果表明,黑斑口虾蛄对盐度适应性较强,盐度暂变时,在盐度14或36仍能存活,仅活力较弱而己。其较适宜的盐度为18~30,该种虽然分布在盐度较高的水域,仍属广盐性种类。其对水温适应性也较强,在水温渐变时,能存活水温为14℃或35℃以上,此时仅是体弱个体有开始死亡现象,如再逐渐提高水温仍能存活。其适宜水温为24~33℃。黑斑口虾蛄对酸碱度的适应能力也较强,能生存在酸性较强的pH5.0,或碱性较强的pH 10.0水环境中,其适宜的pH为7.0~9.0。     

莫桑比克鳗鲡养殖生物学主要特性研究

对莫桑比克鳗鲡（Anguillamor morata）玻璃鳗经形态学鉴定品种后,开展了主要养殖生物学特性研究。耐受高温和低温分别为39℃和7℃,适宜生存水温15℃～33℃;耐受盐度与水温相关,水温30℃致死盐度2．9％,适宜盐度小于1．1％,20℃致死盐度2．7％,适宜盐度小于1．8％,10℃致死盐度2．1％,适宜盐度小于2．0％;耐受pH值与水温相关,30℃致死pH值分别为3．5和11．0,适宜pH值6．0—7．0,20℃致死pH值分别为4．0和11．0,适宜pH值6．0～8．0,10℃致死pH值分别为3．5和10．5,适宜pH值5．5—8．5。常用药物S高聚碘、二氧化氯、三氯异氰尿酸、苯扎溴铵、溴氯海因、甲醛、敌百虫的安全浓度高于或接近常用浓度,硫酸铜、溴氰菊脂乳油、氯氰菊脂、甲苯咪唑的安全浓度低于常用浓度。水体中非离子态氨的安全浓度为2．51mg／L,亚硝酸氮的安全浓度为55．12mg／L。     

罗非鱼养殖技术之五四个关键时期罗非鱼的饲养技巧

罗非鱼属于热带鱼类,对养殖环境及饲养管理要求比较特殊,尤其在亲鱼培育、鱼苗培育、成鱼养殖及越冬保种四个关键时期,要加强饲养管理,以确保增产增收增效益。湖北省英山县水产技术推广站经过20年的罗非鱼养殖及其技术推广,积累了一定的经验,尤其是抓住了这四个关键时期的饲养管理,取得了比较理想的效果。一、亲鱼培育时期罗非鱼适宜生长的水温范围在18℃~38℃,最适生长水温是28℃~32℃;耐低溶解氧,在溶解氧含量低于0.7mg/L水体中仍能摄食,水体溶解氧含量在1.6mg/L时仍能生活繁殖;可在17‰盐度以下的海水中生长、发育和繁殖,能在pH4.5~10…     

白氏文昌鱼幼鱼对海水温度和盐度变化的耐受力研究

研究了厦门海区白氏文昌鱼幼鱼对温度和盐度渐变、骤变的耐受力以及承受低水温后的恢复能力.实验结果显示:(1)14.5～34.0℃是白氏文昌鱼幼鱼生存的安全水温范围,在此水温范围内,无论渐变还是骤变均无碍其生存;白氏文昌鱼幼鱼生存的临界低水温为14.5～13.0℃,而其临界高水温则为34.0～35.5℃;白氏文昌鱼幼鱼对短时间的低水温有较强的耐受力.(2)16.0～31.0是白氏文昌鱼幼鱼生存的安全盐度范围,在此盐度范围内,无论渐变还是骤变均无碍其生存.(3)白氏文昌鱼幼鱼对海水盐度的渐变有较强的耐受力.在渐变条件下,白氏文昌鱼幼鱼可以耐受的临界低盐度为10～7,而其临界高盐度为34～37.     

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.     

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.