拟老年低额溞和大型溞控制水华藻类的实验研究

本文以2种大型浮游动物和1种绿藻、2种铜绿微囊藻为研究对象,初步研究了浮游动物对藻类的摄食关系。实验结果表明当栅藻和无毒铜绿微囊藻CHAB109密度均为1.02×106cells/ml时,拟老年低额溞对二者的去除率分别为54.20%和6.45%,大型溞的则为49.77%和64.77%。同时,拟老年低额溞对栅藻和CHAB109混合藻液中的两种藻均有较好的去除效果,分别为60.65%和34.43%,高于对纯种藻的去除率。在遮光条件下浮游动物摄食量更大,对藻的去除效果更优。拟老年低额溞在锡箔遮光情况下,对初始藻细胞密度为3.023×105cells/ml的有毒微囊藻PCC7806去除率达到32.37%。7d日龄的浮游动物个体大,摄食量也大,有较好的去除效果,且随着添加浮游动物数量的增加,去除率也随着提高。高浓度的藻细胞对两种浮游动物存活率影响较低浓度大。浮游动物应用于藻类水华的控制,作用不容忽视,且若条件适宜,浮游动物也可较好的控制有毒蓝藻。当选用浮游动物控藻藻类水华时,需综合考量选用物种种类、大小、添加数量等因素。     

绿色微囊藻等不同食物对大型溞生长和脂类成分的影响

富营养化在中国是一个突出的环境问题[1],湖泊富营养化问题的核心则是浮游植物的过量生长,目前控制浮游植物过量生长,可通过"生物操纵"[2]的方法进行控制.有许多研究报道:浮游动物是生物操纵的关键因子之一,浮游动物是水域生态系统中主要的次级生产者,在能量传递及物质转换中起重要作用,枝角类是浮游动物的重要组成类群,理论上应该对控制浮游植物的过量生长和控制水华发生方面具有重要作用.     

池塘微囊藻水华防控技术探讨

随着精养池塘富营养化的日趋严重,微囊藻水华也大量出现,微囊藻水华形成后又向水体排放含N、P、C物质和一类单环七肽的生物毒素,加剧水质恶化,给鱼类生长以及渔业生产的发展带来很大的影响。我们从微囊藻水华形成的环境因子入手,应用药物清杀,给全水泥衬砌池塘回填粘土,在池塘底泥中种植小麦,在微囊藻水华大量出现时增放红草鲫鱼等综合方法,成功地抑制了微囊藻水华的形成和发展。     

池塘微囊藻水华的研究与治理

微囊藻是池塘中常见的鱼类不易消化利用的蓝藻。温暖季节 ,该藻易大量繁殖形成水华 ,使其他有益藻类受到严重抑制 ,如微囊藻水华时间很长 ,将影响鱼类 (特别是滤食性鱼类 )生长 ,水华突然消失 ,又易造成水中缺氧或产生有毒物质 ,危及鱼类生存。治理微囊藻水华的方法 ,多用硫酸铜等药物清杀。近年来 ,生产实践中发现以上方法不够理想 ,往往是清杀后不久 ,微囊藻水华照样大量出现。Ｍ .Ｌ .Ｂｈｏｗｍｉｃｋ等曾用Ｋａｒｍｅｘ(敌草隆 )在池塘里进行了清杀微囊藻水华的试验 ,但用药后 ,池水溶氧量由9 5ｍｇ/Ｌ下降到 1 2ｍｇ/Ｌ ,二氧化碳由…     

湖南镇水库浮游生物及其影响因子的典范对应分析

2006年至2007年间调查了蓝藻(Cyanophyta)暴发水体——湖南镇水库的浮游生物群落结构及其变化,研究了其与环境参数之间的关系。调查期间,共鉴定出浮游植物96种(属),浮游动物73种(属)。单位水体浮游植物平均细胞数量变化于0.49×106～16.71×106L-1之间,浮游动物则变化于8～3548L-1之间。春、夏季螺旋鱼腥藻(Anabaena sporoides)水华持续数月,水体表层细胞密度高达2.28×108L-1,进入秋季后其优势逐渐被颤藻属(Oscillatoria)蓝藻取代。典范对应分析显示,浮游植物的季节演替规律与螺旋鱼腥藻数量、总溶解固形物(TDS)和透明度(SD)存在较高的相关性,浮游动物演替主要与溶解在水中的微囊藻(Microcystis)毒素(EMC)、营养盐和螺旋鱼腥藻数量相关。由于高水平营养盐的存在,上行效应无法有效限制蓝藻的发生,水华蓝藻以其数量优势改变了水体理化条件,成为影响浮游植物群落的潜在因素,而营养盐可能通过主导可食藻类的生长,间接影响浮游动物的动态。将水华蓝藻数量及藻毒素浓度作为环境因子进行多元分析,分别提高了对浮游植物、动物群落的解释15.6%和25.8%,说明水华蓝藻和藻毒素的存在对浮游生物群落的组成和结构具有较大的影响。     

红虫作饲料养殖龟鳖效益高

在龟鳖养殖池中，经常会出现红色的小虫在池面、池角成团成片地游动，使池水表面形成一层红色的水华。“红虫”真正的名字叫枝角类，它是水体中浮游动物的一个种类。它由许多浮游蚤类组成，体长平均1mm左右。枝角类的正常体色是灰白色的，只是在水缺氧时才会呈红色，所以“红虫”多发现在臭水沟里。     

虎林市月牙湖微囊藻水华爆发时及其后期的藻类丰度和毒素含量

2013年7月和9月对虎林市珍宝岛湿地保护区月牙湖爆发的惠氏微囊藻Microcystis wesenbergii水华进行调查研究。7月水华爆发时,惠氏微囊藻丰度为75×106~198×106ind·L-1之间,生物量在107.70~284.3mg·L-1之间,微囊藻毒素含量在0~1.84g·L-1之间,严重影响湿地保护区动植物,尤其是野生荷花的生长。而秋季9月微囊藻毒素含量在0.242~0.407g·L-1之间,对人的健康有一定威胁。     

池塘人工培养枝角类的方法及利用

<正> 枝角类通称水蚤,俗称红虫,属小型浮游甲壳动物,体长0.2～1mm,是淡水浮游动物的重要组成部分。枝角类的适应性广、繁殖力强、生长迅速,且营养价值高,干重粗蛋白含量达55％左右,是乌仔、夏花鱼苗的营养丰富、适口、易得的好饵料。但由于条件和种源的限制,天然枝角类资源不能满足育苗、育种生产的需要。因此,池塘人工培养枝角类是解决乌仔、夏花鱼苗定塘开口饵料的重要途径,并能有效地提高池塘育种的规格、产量和效益。我们经过几年来的实验和应用,取得了较好的效果。1 强化培养提高枝角类数量的途径和方法     

曝气对蓝藻门微囊藻属水华形成过程的影响

为研究曝气是否会促进池塘蓝藻门微囊藻属(Microcystis)水华的发生,于夏季在温室内用玻璃缸进行了实验。实验设1个处理组和1个对照组,均不添加沉积物,各组3个重复。对照组不曝气,处理组进行水产养殖池塘中常见强度的曝气,对照组和处理组均添加2次相同的无机氮(N)、磷(P)营养盐。初始时浮游植物以绿藻为优势,随后对照组和处理组中均逐渐形成微囊藻属优势,其在实验后期成为优势最大的种类(平均湿质量浓度为36.28～75.81 mg·L^-1)。对照组的溶解氧质量浓度显著高于处理组(P<0.05),叶绿素a、浮游植物总湿质量浓度、蓝藻湿质量浓度、绿藻湿质量浓度、微囊藻占藻类总湿质量的比例以及浮游动物等均无显著差异(P>0.05)。表明曝气对浮游植物由绿藻门优势向微囊藻优势的转变,即微囊藻水华的形成过程无直接影响;曝气是否存在均可以形成微囊藻优势;曝气主要改变了微囊藻在水中的分布。     

微囊藻水华叠加对太湖沉积物中细菌垂直分布的影响

为研究微囊藻水华爆发对沉积物中细菌的影响,加强对富营养化湖泊细菌生态分布和环境调控原理的认识,选取太湖竺山湾沉积物柱状样,经添加高浓度微囊藻培养后,采用聚合酶链式反应-变性梯度凝胶电泳（polymerase chain reaction-denaturing gradient gel electrophoresis;PCR-DGGE）方法,分析细菌在沉积物中的垂直分布特征。结果显示,微囊藻水华叠加对于沉积物剖面表层细菌群落结构影响很小,对沉积物中细菌垂直分布的影响不大,仅在7～9cm深度之间有一定影响。     

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.     

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.     

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.     

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).