冬季鱼病的防治方法

鱼类越冬期指每年12月至翌年3月,同时,这也是冬季鱼病流行的季节,在有病原菌存在的情况下,鱼病都是在一定的温度范围内发生的,一般低温常见的鱼病有斜管虫病、小瓜虫病、粘孢子虫病、口丝虫病、肤霉病、锚头蚤病、三代虫病、竖鳞病等。 1、斜管虫病,流行在初冬和春季,适宜水温12-18℃,低于8-11℃时,仍可大量出现。在华东,华中地区3-5月间此病最流行。华南地区冬春两季适宜繁殖。20℃以上不易发生。 斜管虫病的病原体是鲤斜管虫,大量侵袭皮肤和鳃时,表皮组织因受刺激而分泌大量粘液,同时组织被破坏,严重影响鱼的呼吸机能,随着大批死亡,在鱼苗、鱼种阶段特别严重。防治方法:①采取石灰彻底清塘消毒;②鱼种或亲鱼如发现有病原体,用8ppm硫酸铜或2ppm硝酸亚汞给鱼浸洗约30分钟;③用0.7ppm硫酸铜或硫酸铜和硫酸亚铁合剂(比例为5:2),全池遍洒,有杀灭效果。     

翘嘴红鲌小瓜虫病的防治

在进行翘嘴红鱼白鱼苗铒料配方的筛选实验中 ,实验鱼感染了小瓜虫 ,分别采用如下方法进行治疗 :1 .5ppm的亚甲蓝浸泡 4天 ;2 .3%的食盐溶液浸泡 3min ;3 .0 5ppm的福尔马林溶液浸泡 3min。 4 .0 1ppm的硝酸亚汞溶液长期浸泡 (1星期以上)。结果为 :亚甲蓝浸泡 4天 ,患病鱼无好转 ,第 3天开始逐渐死亡 ,4天内全部死亡 ;用食盐和福尔马林溶液浸泡 3min,患病鱼即全部死亡。对用以上 3种药物处理后的鱼体进行镜检 ,发现鱼体上的小瓜虫体无明显减少。用硝酸亚汞浸泡的鱼 ,治疗期间死亡 2尾 ,镜检鱼体上无虫体。结论是 :患小瓜虫病的翘嘴红鱼白 ,不宜用亚甲蓝、食盐或福尔马林 ,采用 0 1ppm的硝酸亚汞溶液长期浸泡较为有效     

翘嘴红Bai小瓜虫病的防治

在进行翘嘴红Bai鱼苗铒料配方的筛选实验中，实验鱼感染了小瓜虫，分别采用如下方法进行治疗：1．5ppm的亚甲蓝浸泡4天，2．3％的食盐溶液浸泡3min；3．0，5ppm的福尔马林溶液浸泡3min.4. 0.1ppm的硝酸亚汞溶液长期浸泡（1星期以上），结果：为亚甲蓝浸泡4天，患病鱼无好转，第3天开始逐渐死亡，4天内全部死亡，用食盐和福尔马林溶液浸泡3min，患病鱼全部死亡，对用以上3种药物处理后的鱼体进行镜检，发现鱼体上的小瓜虫体无明显减少，用硝酸亚汞浸泡的鱼，治疗期间死亡2尾，镜检鱼体上无虫体，结论是：患小瓜虫病的翘嘴红Bai，不宜用亚甲蓝，食盐或福尔马林，采用0．1ppm的硝酸亚汞溶液长期浸泡较为有效。     

小鳄龟纤毛虫病的防治研究

为筛选孔雀石绿的替代药物,探索小鳄龟纤毛虫病的有效治疗方法,比较了几种常见药物对小鳄龟纤毛虫病的治疗效果及对龟摄食和活动的影响。结果表明,高锰酸钾疗效最好,其次为氯化钠、甲醛溶液,聚维酮碘和硫酸铜无明显疗效;氯化钠和甲醛溶液对龟摄食、活动等影响较大。生产上可采用75g/m~3的高锰酸钾浸洗30分钟防治小鳄龟的纤毛虫病。     

福尔马林防治鳜鱼苗纤毛虫病效果好

生产上常采用0．7ppm的硫酸铜、硫酸亚铁（5：2）全池泼洒法防治想鱼苗纤毛虫病。笔者在生产实践中亦尝试采用福尔马林金池泼洒法进行治疗，取得较好的治疗效果。过程如下：药物泼洒前，首先关闭水闸停止流水，全地泼洒福尔马林使浓度呈40PPm，保持药物的有效浓度1小时后再开闸流水排除剩余福尔马林。至傍晚，以同样方法再次进行治疗。第3天开始每天用30～40PPm的福尔马林静水泼洒，直至鱼苗生长到长为2．5～3·0厘米的夏花。笔者也曾使用福尔马林防治想鱼夏花、罗氏沼虾等特种水产动物的纤毛虫病，都收到较好的治疗效果。生产上为了确保…     

淡水鲳对九种常用鱼药的敏感性试验

本文报告了敌百虫、孔雀石绿、硝酸亚汞、漂白粉、呋喃唑酮、生石灰和食盐等常用鱼药对淡水鲳的安金浓度依次为0.028ppm、0.0312ppm、0.0865ppm、0.699ppm、16.22 ppm、19.5 ppm、1040 ppm。淡水鲳分别在亚甲基蓝2.1 ppm,硫酸铜硫酸亚铁合剂(5∶2)5.6ppm药液中浸浴240小时,未见异常反应。     

斑鳜鱼苗对6种常见药物的忍受力实验

用敌百虫、硝酸亚汞、孔雀石绿、硫酸铜和硫酸亚铁合剂、漂白粉、食盐6种药物对斑鳜鱼苗进行毒性实验。测得6种药物在水温21~22℃时对平均全长为(1.0±0.1)cm的斑鳜鱼苗的安全浓度依次分别为0.058、0.046、0.073、0.32和1.747 mg/L。斑鳜鱼苗对敌百虫等6种药物的敏感性与一般养殖鱼类不尽相同,根据已求安全浓度与常见遍洒剂量相比较,得出斑鳜鱼苗对6种药物的敏感性大小依次为:硝酸亚汞>敌百虫>孔雀石绿>硫酸铜合剂>漂白粉>食盐。     

不同药物对金鱼小瓜虫病的防治效果

研究了硝酸亚汞、孔雀石绿、亚甲基兰、福尔马林、硫酸铜与硫酸亚铁合剂、生姜和辣椒合剂对金鱼小瓜虫病的防治效果。试验结果表明,硝酸亚汞、孔雀石绿、福尔马林对金鱼小瓜虫病的防治效果较好,而硫酸铜与硫酸亚铁合剂质量浓度小于1 0mg/L时,不仅不能杀死小瓜虫,反而刺激小瓜虫胞囊的形成,加速繁殖。只有当其质量浓度达到1 2mg/L时,才能有效地杀灭小瓜虫。     

孔雀石绿治疗小瓜虫病试验

小瓜虫病的病原体是纤毛虫纲多子小瓜虫(Ichthyophthirius multifiliis Fouquet)。它是池塘养鱼中一种常见的流行病，一般在春末夏初的鱼苗、鱼种培育池里发生，以致引起鱼苗鱼种大量死亡。中国科学院水生生物研究所曾发表过文章，阐述可用硝酸亚汞浸洗或泼洒的办法进行防治，其他单位也曾报导过一些用药物防治小瓜虫病的方法。     

3种重金属对瓦氏黄颡鱼的急性毒性试验

在室内常温静水条件下,采用氯化镉、硫酸铜、硝酸亚汞3种重金属盐类对瓦氏黄颡鱼进行了毒性试验。试验结果表明,3种药物的毒性强弱依次为:硝酸亚汞>硫酸铜>氯化镉。安全质量浓度分别为:硝酸亚汞0.0036 mg/L、硫酸铜0.1501 mg/L、氯化镉8.6372 mg/L。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

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 performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

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).     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

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.     

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.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.