螺旋式射流增氧机

水中增氧主要有三种方法。一是生物增氧方法,二是物理增氧方法,三是化学增氧方法。用增氧机向水中增氧就是一种物理增氧方法。目前我国广大科技人员开发了众多形式和型号的增氧机。这些增氧机主要有三种增氧功能。一是增加水和空气的接触面积,利用机械能将水喷到空气中,或形成飞溅的小水珠,增加水和空气接触面积,使空气中氧有更多机会渗入水中。二是利用正负压力,将空气压入或吸入水中。三是促进上、下水层水的流动,将上层溶氧高的水和下层溶氧低的水混和交换,使上、下层水溶氧相近。这不但能避免表面过饱和氧向空气中逸     

鱼塘自动增氧系统的设计

1 概述 鱼类的生长与外界环境条件有着密切的关系,与鱼类生长有关的环境条件很多,在正常情况下,影响较大的为水温、溶氧等。本文着重从水中溶解氧对鱼类生长的影响出发,提出一种适合养殖鱼塘中使用的自动增氧装置。 凡空气中的气体一般都能溶于水中,但主要是氧、氮气和二氧化碳,而氧气是直接影响鱼类及其它水生动物的生命活动的物质。水中的溶解氧来源于空气及水生植物的光合作用。空气中溶解于水中的氧,当水面静止时,其数量是很少的,并且只限于水表层,而水生植物的光合作用是水中含氧的主要来源,由于植物光合作用的昼夜变化而使水中的含氧量也随昼夜变化。由此可知,水中含氧量在清晨日出之前最低,所以水中缺氧往往都是发生在后半夜或黎明之前。     

影响活鱼运输效率及成活率的主要因素

1溶解氧提高活鱼运输成活率和效率的关键之一是水质,其中溶解氧尤为重要。活鱼运输中由于水体大小的限制,水体中原有的溶氧量远远满足不了运输鱼类的需要。目前国内现有的增氧措施主要是通过空气压缩机向水中充入空气,或用氧气瓶通过石墨、金刚沙充气石、碳棒及扎眼的胶管向水中输入纯氧,这些增氧措施在一定程度上可以缓解活鱼运输的压力,但是并没有从根本上解决问题。因为无论通过什么样的方式把空气中的氧气溶解到水中,最多也只能达到氧气在空气中的饱和度,即8.5克/米3,而其余时间充气泵都在做无用工,白白耗电,造成极大的浪费。此外空气中…     

节能弥散型增氧机械的工作原理及应用

一、弥散增氧机械的工作原理 弥散型增氧机械的工作原理是将富含氧气的空气用鼓风机或其他设备送入输气管道，输气管道将空气送入微孔管，微孔管将空气以微气泡的形式喷射到水中，从而达到向水体中增氧的目的。微孔管是一种由橡塑材料制成，     

水中溶解氧的变化规律及其影响

溶解氧是指以分子状态溶存于水中的氧气单质。水中的溶解氧含量通常很低,只有百万分之一。水中有机物分解、生物呼吸、气压、盐度等许多因素,都对水中溶解氧产生影响。所以掌握水中溶解氧的动态规律,熟悉缺氧的     

养鱼增氧技术

养鱼先养水,而水中溶解氧是水质的一项非常重要的指标。首先,氧气是鱼类生存所必需的条件;其次,氧气还要保证鱼类生长、摄食、消化代谢的需要。氧气充足,鱼才能积极摄食,提高消化吸收率,快速生长。例如鲫鱼在溶氧0.5-2mg/L时的饵料系数是溶氧3-6mg/L时的2倍。其次,水中的各种生物（藻类、     

养殖鱼类越冬期的增氧方法

鱼类越冬是东北地区池塘养鱼生产的一个非常重要的环节,任何失误都会造成越冬鱼类死亡,给渔业生产带来损失,因此掌握越冬期的增氧方法十分必要.通常情况下,池塘中溶解氧的来源有三种:一是从空气中直接溶解,通过风浪的作用,使水和空气接触,空气中的一部分氧气就溶入水中,增氧机就是运用这个原理.二是光合作用增氧,这是主要来源,约占池塘水中溶氧的90％.三是补水增氧,利用自然的流水或是人工的注水来增加溶解氧.     

专家咨询服务台

1.鱼类越冬池为什么要及时扫雪?答:在自然情况下,水中溶解氧的来源有两个方面,一方面是通过空气中的氧向水中扩散溶解。另一方面是通过水中浮游植物光合作用产生氧气。对于养鱼水体而言,光合作用产生氧气是水中溶解氧的重要来源。在鱼类越冬期间,由于冰面的封隔作用,如果不采取人工机械增氧,冰下水体依赖浮游植物光合作用产生氧气是水体氧气补充的唯一来源。因此,在鱼类越冬期间,及时地对覆盖在越冬池冰面上的积雪进行清扫,对保证冰面     

虹吸式增氧泵受用户好评

天津市河东农牧渔机厂生产的虹吸式多功能增氧泵,为专利产品,该机以灵巧的结构,通过负压进气,高压切割,微孔曝气等手段,强制空气中的氧进入贫氧水中,实现气相向液相的转移,增加水中溶氧,调节水质,满足鱼虾高密度养殖的需求。 1988年天津市水产研究所在养殖淡水白鲳鱼试验中,使用0.55瓩虹吸式增氧泵,获得亩净产千斤以上的好收成。经该所测定,在0.75亩试验池内,放养鱼种4000尾,开机半小时,溶氧可提高1mg/l;开机一小时,溶氧提高2mg/l。     

夏季鱼塘增产技术

<正>一、增氧夏季气温炎热,有时甚至干燥闷热。在这个季节容易发生缺氧问题。众所周知,水中的溶解氧是鱼类赖以生存的必要条件之一。在集约化养殖的鱼塘,由于密集和数量种类多,容易造成溶解氧在局部范围内出现不足,严重的可能会导致泛塘现象。因此,必须提供充足的溶解氧。水体增氧的途径有以下几种:1.空气中氧气的溶解如果水体中的溶解氧没有达到饱和,空气中的氧气就会不断地溶解到水中。但是,仅仅靠空气自然溶解到水体的溶解氧只限于水体     

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.     

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.     

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).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

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.