黑鲷鱼种低盐度培育试验

海盐县地处杭州湾北岸,常年海水盐度4～10。2003年至今我们在海盐县秦山镇杨柳山村对虾养殖基地进行黑鲷低盐度养殖试验,取得了良好的效果,现将2005年低盐度黑鲷鱼种培育试验报告如下。一、材料及方法1.池塘条件试验池塘是多年的对虾养殖池,面积为6.5亩,清整消毒是冬季伴随虾塘     

长毛对虾北移养殖初试

从浙江温州购进０．７ｃｍ长毛对虾苗１４万尾,暂养和盐度驯化后在５亩池塘养殖６３天,平均体长由１．２ｃｍ,增至８．４ｃｍ,旬增长１．１４ｃｍ。至９月底收获时,平均体长１０．５ｃｍ,亩产６２ｋｇ,亩效益６４０元。     

刀额新对虾对淡水的适应性观察

刀额新对虾原本生活于海水中，其人工育苗盐度一般为２５‰左右，要放养到淡水中养殖必须先经过一段时间的淡化，使其逐渐适应淡水环境，这是刀额新对虾淡水养殖成功与否的关键。现就该虾对淡水的适应性观察结果报告如下。一、材料与方法１．虾苗来源１９９８年５月１６日从厦门购进３００万尾规格为平均体长０．３ｃｍ的虾苗，测定海水盐度为２４‰。２．不同淡化速度观察经同等盐度暂养一天后，取１５０尾分成３组，１组和２组每６小时降低盐度２‰，３组每６小时降低盐度１‰，每隔２４小时计算一次存活数。每次换水后适量投喂丰年虫无节…     

南美白对虾池塘对淡养殖综合措施

一、前期准备１．虾池准备池塘要求水源充足，注排水方便，且注排水口分开，水质良好，虾池面积一般要求５～１０亩，池深１．５～２．５米，池埂坡度１∶（２～２．５）。每一个养殖周期开始前均须彻底清塘，清除池底污物和敌害生物，为对虾的栖息和生长营造一个良好的外部环境。２．纳水、配水和肥水在池塘一角用塑料薄膜围出约占整个池塘大小１／１０的面积，作为暂养淡化区。放苗前１０～１５天池塘进水５０厘米，在暂养区内投入一定量的日晒盐、氯化钾、氯化镁等氯化物，使暂养区水体盐度与苗场出苗池水盐度差小于１‰。配水结束后，利…     

池塘半封闭淡化养殖斑节对虾试验

探讨了在池塘条件下半封闭式淡化养殖斑节对虾的技术，成功地将斑节对虾养殖环境的盐度下限控制在1～2。通过培养基础饵料、科学驯养和使用微生物制剂等手段，使对虾的平均单产达到了3812kg／hm^2，产值达到10．8万元／hm^2。     

雨季养虾须预防应激

一、雨季引起对虾应激的原因1.盐度的变化南美白对虾放苗后逐渐降低池塘水体的盐度,有助于养殖的成功。但是,雨季,特别是雷阵雨、暴雨,常常出现对虾养殖池塘、近海的海水盐度急速下降。雨水是纯淡水,在无风、无增氧的状态,     

微生态制剂在甲壳动物养殖中的应用研究

在甲壳动物养殖中使用微生态制剂取得良好效果。南美白对虾室内养殖GMA1组、GMA2组及DY－1组的养殖成活率分别为95％．79％、91．78％和88．00％，均高于对照组的81．67％，微生物及水化学指标也明显优于对照组；池塘养殖中国对虾45d，试验组和对照组对虾平均体长分别增长2．86cm和2．40cm；河蟹育苗试验组比对照组提高成活率27．78％，本文还对微生态制剂的作用机理和使用注意项等进行了论述。     

多种鱼虾混养新模式

<正>目前对虾养殖的主要品种是南美白对虾。我们通过多年的对虾养殖研究工作,对不同的养殖模式进行试验分析,提出多种鱼与对虾混养,主养品种对虾,养殖过程少换水或不换水、一年一造的养殖模式,养殖三年,每年获得好效益。1.放苗前准备1.1池塘结构对虾养殖池1#号池8亩、2#号池10亩都为长方形钝角南北向,水深     

半滑舌鳎与中国对虾池塘混养技术

在半滑舌鳎养殖池中适当混养中国对虾,对虾可摄食鱼的残食,既节省饵料又改善池底环境,并可取得鱼、虾双丰收的成效,具有广阔的前景。1养殖池的选择1.1水源条件选择水源充足、潮流畅通、无污染,水质清新、悬浮物少、交通便利的地方;盐度在15‰～34‰。1.2养殖池条件进排水渠道分开,避免养殖用水污染;池塘无渗漏,池塘底质为沙底、沙泥底或泥沙底质为佳,利于鱼伏底潜沙。养殖池的规格以3～10亩为佳,也可利用现有的对虾养殖池进行改造;养殖池形状以长方形或长条形、平均水深以1.2m以上为好,设进排水闸门,进排水要流畅,排水时能将池水迅速全部排…     

梭子蟹人工养殖

三疣梭子蟹简称梭子蟹,是著名大型海产食用蟹类。其对环境变化的适应性强,生长速度快,是养殖的适宜品种。一、养殖池的选择梭子蟹养殖地以土地为佳,池塘结构基本上同我国半精养对虾土地相类似,也可利用现有对虾养殖池进行改造从事梭子蟹养殖。面积可根据生产规模而定,以中、小型养殖池为宜,水深l．5－2米。为保持良好的水质,养殖地要能够充分换水,可以彻底排水。梭子蟹多喜浴池边栖息,应考虑尽量增加边坡面积,以避免过分密集。梭子蟹有潜砂习性,池底铺设10cm厚的中。粗砂为好,但不要铺平,做成小砂堆状,以促使其潜砂栖息,减…     

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.     

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.     

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 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).