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.     

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.     

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.     

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.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.