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1.
Wild‐catch eels with low fat content are either not accepted at all or accepted as a lower‐quality and less valuable product in the global eel market. This study was undertaken with the goal of increasing the fat content of yellow shortfin eel, Anguilla australis (104 ± 11 g initial weight), captured in the wild and kept in captivity for a short period, as well as assessing their rate of growth. An 86‐d feeding trial was conducted indoors in a recirculation aquaculture system, at 25.5 ± 1.6 C. Two commercial extruded dry feeds were tested; one formulated for European eel and one not specifically intended for use on eels. Good values of specific growth rate (1.10 and 1.12%/d) and feed conversion ratio (1.01 and 1.10) were achieved with both tested feeds. At the end of the trial, eels achieved 20–22% total fat, starting from wild fish with 7% fat content. Fat quality of the fattened eel was appreciably superior (higher proportion of omega‐3 fatty acids) than the fat of eels captured in the wild. The results of this study are encouraging for the prospect of fattening yellow shortfin eels and obtaining a market‐oriented eel product.  相似文献   

2.
为了调节循环水系统中养殖水体的pH,根据气体交换原理,设计一种脱二氧化碳(CO_2)装置。采用该装置去除养殖水体中的CO_2,并对由于CO_2含量累积造成的pH下降进行调节,使养殖鱼类处在一个适宜的pH环境中。试验时水温控制在(25±0.5)℃,每1 h取水样测1次pH,每4 h测1次碱度。水样取自养鱼桶内的水,检测前先对水样用40μm孔径针头过滤器进行过滤处理,实验周期24 h。结果显示,循环水系统加装脱二氧化碳装置能有效去除CO_2,使水体稳定在一个适宜的pH范围(7.39~7.42);CO_2质量浓度呈降低趋势,24 h后由开始的13.16 mg/L降低到7~8 mg/L,降低近50%,而不加装脱二氧化碳装置的循环水系统CO_2质量浓度持续上升,24 h后增加到37 mg/L左右,pH持续降低,最终降低到6.72~6.81。研究表明,脱二氧化碳装置能够有效去除水体中的CO_2,使水体pH维持在一个适宜鱼类生长的范围。  相似文献   

3.
Furazolidone, an antibacterial drug that was once widely used in the livestock industry and aquaculture, is now prohibited in numerous countries. It is difficult to detect residual furazolidone because it is readily metabolized in animal tissues but, by using and liquid chromatography coupled with tandem mass spectrometry, its metabolite, 3-amino-2-oxazolidinone (AOZ) can be detected. Here we describe the validity of an enzyme-linked immunosorbent assay (ELISA) kit to detect AOZ in Japanese eel Anguilla japonica tissue. ELISA is capable of detecting AOZ at 1.0 μg/kg in an eel sample with excellent accuracy and precision. Our results show that ELISA is suitable for regulatory purposes and for studying the fate of AOZ residues in eel treated with furazolidone. To measure the persistence of AOZ in eel tissues, eels (1.4–6.5g) were immersed in tanks containing 2 and 10 mg furazolidone/L for 3 h, and then maintained in a tank supplying well water for the next 160 days. The half-lives of AOZ, calculated from the linear terminal part of the excretion curve, were 25.0 days in muscle and 21.6 days in liver from fish exposed to 2 mg/L furazolidone. In the eels treated with 10 mg/L furazolidone, by contrast, high levels of AOZ were detected in liver and muscle, but the half-lives of AOZ were similar to those in fish treated with 2 mg/L furazolidone. The half-lives of AOZ in eel tissues were prolonged by the condition of low water temperature.  相似文献   

4.
One of the challenges that Recirculating Aquaculture Systems (RAS) are still facing is the risk that in RAS fish grow less than in flow-through systems due to the accumulation of substances originating from feed, fish or bacteria associated with the water re-use. The present study investigated whether RAS with high and low accumulation levels of these substances affect feed intake and growth of Nile tilapia Oreochromis niloticus, African catfish Clarias gariepinus, and European eel Anguilla Anguilla. One-hundred and twenty individuals of each species were used (start body weights: Nile tilapia 264.8 ± 8.3 g; African catfish 253.2 ± 2.1 g and European eel 66.6 ± 1.3 g). For a period of 39 days, growth and feed intake were compared between high and low accumulation RAS. HIGH accumulation RAS was designed for maximal accumulation of substances in the water by operating the system at nearly-closed conditions (30 L/kg feed/d), using mature biofilters and high feed loads; and (2) LOW accumulation RAS was designed to be a proxy for flow-through systems by operating at high water exchange rates (1500 L/kg feed/d), new biofilters and low feed load. HIGH accumulation RAS induced a reduction in feed intake (42%) and growth (83%) of Nile tilapia, as compared to systems that are a proxy for flow-through conditions. This effect was not observed in European eel and African catfish. The cause of this reduced feed intake and growth rate of Nile tilapia is still unclear and should be addressed in further studies.  相似文献   

5.
A sustainable aquaculture production involves alternatives, as recirculating aquaculture systems (RAS), in order to increase the water supply efficiency. This paper aims: a) to propose a method for dimensioning a RAS filled and additionally supplied with water from a rainwater harvesting systems (RHS) and; b) to evaluate the efficiency of the system based on the supply of rainwater from the RHS, the quality of water in the RAS, and the development of aquatic organisms. A pilot aquaculture farm for rainbow trout (Oncorhynchus mykiss) production was designed and dimensioned. On one hand, the RAS with a configuration based on a treatment tower provided acceptable values of pH, TAN, and alkalinity. The temperature was slightly above the recommended temperature but did not negatively impact trout development. On the other hand, the water use efficiency reached 178 L/kg of fish, instead of 210,000 L/kg in an open flow system for trout rearing. The RHS fulfilled the additional required water on the test period of the pilot farm and is expected to supply at least 92% on average during the useful life. Regarding the aquatic organisms’ development, the system allowed both a better Length/ weight ratio and a lesser mortality rate compared to previous studies of RAS. In contrast to other studies in the literature, the mathematical models for dimensioning the system were calculated as a function of the final biomass expected in the tank instead of the quantity of supplied feed. Therefore, this method confirmed the applicability of this alternative criterion for designing biofilters and aquaculture systems.  相似文献   

6.
Peracetic acid (PAA) is an effective disinfectant/sanitizer for certain industrial applications. PAA has been described as a powerful oxidant capable of producing water quality benefits comparable to those expected with ozone application; however, the water oxidizing capacity of PAA in aquaculture systems and its effects on fish production require further investigation, particularly within recirculation aquaculture systems (RAS). To this end, a trial was conducted using six replicated RAS; three operated with semi-continuous PAA dosing and three without PAA addition, while culturing rainbow trout Oncorhynchus mykiss. Three target PAA doses (0.05, 0.10, and 0.30 mg/L) were evaluated at approximately monthly intervals. A water recycle rate >99% was maintained and system hydraulic retention time averaged 2.7 days. Rainbow trout performance metrics including growth, survival, and feed conversion ratio were not affected by PAA dosing. Water quality was unaffected by PAA for most tested parameters. Oxidative reduction potential increased directly with PAA dose and was greater (P < 0.05) in RAS where PAA was added, indicating the potential for ORP to monitor PAA residuals. True color was lower (P < 0.05) in RAS with target PAA concentrations of 0.10 and 0.30 mg/L. Off-flavor (geosmin and 2-methylisoborneol) levels in culture water, biofilm, and trout fillets were not affected by PAA dosing under the conditions of this study. Overall, semi-continuous PAA dosing from 0.05-0.30 mg/L was compatible with rainbow trout performance and RAS operation, but did not create water quality improvements like those expected when applying low-dose ozone.  相似文献   

7.
Abstract  Growth of American eels, Anguilla rostrata (Lesueur), sampled in saltwater bays and adjacent freshwater ponds in the southern Gulf of St. Lawrence, Canada, was estimated by otolith annulus back-calculation, and related to salinity of growth habitat as determined using otolith strontium:calcium ratios. Eels resident in salt water grew on average in length 2.2 times faster than freshwater residents and increased in weight 5.3 times faster than freshwater residents. Previous findings of superior American eel growth rate in brackish water are thus extended to full-strength salt water. Freshwater residents took an estimated 2.4 times longer than saltwater residents to reach the silver eel stage. The extended time to maturation of eels reared in fresh water increases their vulnerability to fisheries and to bio-accumulation of contaminants. Freshwater eel populations should be managed more conservatively than those in saline waters. The increase in eel growth with salinity suggests that rearing in brackish or salt water could improve growth rates in eel aquaculture.  相似文献   

8.
Nitrogen (N) and phosphorus (P) budgets in a bioflocs technology (BFT) aquaculture system and a recirculation aquaculture system (RAS) during over-wintering of tilapia (GIFT Oreochromis niloticus)for 64 d were compared in the current study. Fish feed was the major input of N in both systems, specifically, 94±0 % and 82±4 % for the RAS and BFT aquaculture system, respectively. The rate of N recovery in the BFT aquaculture systems was estimated to be 48±5 % of input N, which was significantly different from that of the RAS (37±4 %). There was no significant difference between the RASs and BFT aquaculture systems in terms of P recovery rate. The regular backwashing of the drum filter and biological filter in RAS accounted for 41 ± 2 % of input N and 39 ± 2 % of input P. Approximately 54 % of unassimilated nitrogen N was removed by nitrification in the BFT aquaculture systems. The results from the present study suggest that nitrification may be the dominant pathway for ammonia removal in a BFT aquaculture system rather than by heterotrophic bacterial assimilation.  相似文献   

9.
Water quality management is important in cage culture of the Asian swamp eel (Monopterus albus). However, it is difficult to manage water quality after a large number of eels have died within the cages. The present study seeks to solve this problem by establishing a method to judge and maintain water quality. To this end, the effect of temperature and eel body weight on the water quality and microorganisms after the death of Asian swamp eels have been examined in the laboratory. The results showed that the changes in water quality parameters were similar at different temperatures and different eel weights. For example, at 26°C, the water quality started deteriorating at 5–7 days after death, which corresponded to the oxygen consumption stage. This was followed by the anaerobic decomposition stage at 11 days after death, at which point the self‐purification process of the water body was initiated. Under a lower temperature of 18°C, the oxygen consumption stage and, therefore, the overall decomposition process were extended. Proteobacteria, Bacteroidetes and Verrucomicrobia were the dominant phyla detected during the decomposition process, but the relative proportions of the dominant families differed across the stages. Based on these findings, we have provided innovative suggestions for water quality detection and management in Asian swamp eel production: (i) at a water temperature of 16–23°C, the following measures should be taken to deal with dead eels 15 days after the introduction of seedlings: (a) at an ammonia nitrogen level higher than 2 mg/L, the bodies present at the bottom of the cage need to be fished out with a net. However, when the ammonia nitrogen level is not higher than 2 mg/L, the whole cage should be sprayed with detoxifying substrate improver or Bacillus powder, according to the instructions, to improve water quality. (ii) At a water temperature of 23–30°C, the above measures should be taken on the 6th day after the seedlings are released, provided the critical value of ammonia nitrogen is 1.57 mg/L. An important limitation of this study is that water exchange was not possible under the laboratory experimental conditions, and the deterioration of water quality caused by eel death may have been alleviated due to water exchange between the inside and outside of the cage.  相似文献   

10.
工厂化循环水养殖系统得到越来越广的应用,去除水体中有机物的重要性逐渐得到人们的重视,但去除有机物的主要设备———泡沫分离器在技术应用上还不成熟,本文通过实验逐步改变充气量、水流量、有机物浓度、分离器高度等影响因素,以确定这些影响因素对泡沫分离器有机物去除效率的影响,研究结果表明:(1)由于气流紊动的影响存在最佳气液比,本实验中气液比为6时有机物去除率最大。(2)有机物浓度是影响有机物去除效率的主要因素,本实验中当有机物浓度在4.32mg/l时去除率明显增大。(3)分离器高度对去除率的影响是随着有机物浓度等因素的变化而不同。  相似文献   

11.
建立了固相萃取-液相色谱串联质谱法(SPE-LC-MS/MS)同时检测养殖海水中17种喹诺酮类药物残留的分析方法。海水经酸化处理后,采用HLB固相萃取柱富集、净化目标化合物,通过对比水样在不同上样pH、淋洗液与洗脱液等条件下的回收率,以此对前处理方法进行优化。收集到的洗脱液经氮气吹干后用流动相定容至1 ml,待测。色谱流动相A相为0.1%甲酸水溶液,B相为乙腈,所有药物经梯度洗脱进行分离,在LC-MS/MS正离子模式的多反应监测模式下进行定性定量分析。17种化合物可以在10 min中内得到较好的分离,线性范围为1–200 ng/ml,线性相关系数均大于0.999,检出限均在2–10 ng/L范围内,定量限均在5–20 ng/L范围内。以空白海水为基质,在20、100、200 ng/L三个不同添加水平下采用内标法定量的加标回收率均在71.3%–125.0%范围内,相对标准偏差(RSD)为2.44%–12.27% (n=5)。采用该方法对黄海灵山湾近岸4个养殖场进行海水采集并检测,共检测出4种喹诺酮类药物,分别是恩诺沙星、氧氟沙星、诺氟沙星和环丙沙星,其中,恩诺沙星浓度最高。研究表明,该方法快速、可靠,适用于养殖海水中喹诺酮类药物的检测。  相似文献   

12.
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13.
鳗鱼饲料添加稀土甲壳素的应用研究   总被引：19，自引：0，他引：19  
在国产鳗鱼饲料中添加稀土甲壳素，可使僵鳗在２０天内生长复苏和体色好转，日增长率比对照组提高３．２５至４．６０倍。正常鳗种摄食稀土甲壳素后，可起到增强体质，促进生长的作用，日增长率比对照组提高２２．５－２９．０％。在国产饲料中添加１－１．５％的稀土甲壳质，饲料系数在僵鳗可降低６９．２８％，正常鳗种可降低２６．４７％，基本上可以取代进口饲料。  相似文献   

14.
Intensive recirculating aquaculture systems (RAS) with its hyper-eutrophic water offer ideal conditions for bacterial growth, abundance and activity, potentially affecting fish and system performance. Feed composition and feed loading in particular will have significant impact on organic and inorganic nutrients available for microbial growth in RAS. How these nutrient inputs affect and regulate bacteria in RAS water is, however, unclear. To investigate this relationship and the associated water quality dynamics, the effects of altered feed loading on microbial water quality in RAS was studied.The study included six independent, identical pilot-scale RAS, each with a total volume of 1.7 m3 (make-up water: 80 L/day) stocked with juvenile rainbow trout (Oncorhynchus mykiss). All systems had been operating with constant and identical feed loading of 3.13 kg feed/m3 make-up water for a period of three months before the experiment was initiated. Three controlled levels of feed loading where established in duplicates: no feed (0 kg feed/m3), unchanged feeding (3.13 kg feed/m3), and doubled feeding (6.25 kg feed/m3). The experimental period was seven weeks, where microbial and chemical water quality was monitored weekly. Bacterial activity was measured using Bactiquant®, and microbial hydrogen peroxide degradation. Bacterial abundance was quantified by flow cytometry, and water quality parameters by standardized methods The study showed that water quality as well as bacterial activity and abundance were affected by the changes in feed loading. The microbial water quality parameters, however, did not respond to feed loading changes as quickly and straightforward as the physicochemical parameters such as nitrate, chemical oxygen demand and biological oxygen demand. It was presumed that the fixed bed biofilter suppressed microbial response in the water phase. Hydrogen peroxide degradation assay proved to have considerable potential for assessing overall bacterial load in RAS water although further adjustments and standardization procedures are required.  相似文献   

15.
国外封闭循环水养殖系统工艺流程设计现状与展望   总被引：3，自引：0，他引：3  
宋奔奔  吴凡  倪琦 《渔业现代化》2012,39(3):13-18,39
以发达国家成功运行的养殖系统为出发点,按照不同养殖鱼类的生活习性、水体流态以及水处理工艺特性的不同,将其归类为4种典型鱼类的循环水养殖系统工艺(常规游泳性鱼类、鲆鲽类、鲑鳟类、鳗鲡等),分析探讨每种工艺的设计理念、设计思路等,总结工艺流程设计技术特征,展望未来发展趋势,提出循环水养殖工艺流程设计较为特殊的3种模式,从而为封闭循环水养殖系统设计提供技术参考。  相似文献   

16.
The Asian swamp eel (Monopterus albus) is a high protein content fish with delicious taste that can survive for 6–8 months. The growth performance and nutrient quality of Asian swamp eels in a freshwater aquaculture system in Central Java, Indonesia was studied using a completely randomized design. Golden snails, snails, silkworms, and earthworms were the feeding treatments at 5% of total body weight. The test animals weighed 5.68 ± 0.35 g after a 60-day culture, and the density was 36 eels/m2. Providing different types of feed had significant effects (P < 0.05) on relative growth rate (RGR), feed intake, and survival rate (SR) but did not significantly affect the protein efficiency ratio (P > 0.05). The best final weight, RGR, and SR results were 11.80 g, 2.64%, and 80.95% during a 60-day culture with silkworms used as feed. The nutrient quality in a similar treatment found with the best proximate composition was 76.90% protein, 3.24% fat, 25.19% palmitic acid, 15.41% oleic acid, 15.9% glutamic acid, 8.2% isoleucine, and 8.9% lysine.  相似文献   

17.
Under aquaculture conditions, European eels (Anguilla anguilla) produce a high percentage of males (80–95%) that normally stop growing at 100–200 g. Females continue to grow to 500–750 g and obtain higher market value. Therefore, increasing the percentage of females in a population would be beneficial to the culture of eels. The present study was carried out in order to examine the effect of oestradiol and phytooestrogens on sex differentiation and growth rate of eels. Juvenile European eels with undifferentiated gonads were fed pellets containing oestradiol‐17β (E2) or phytooestrogens for 100–150 days. Feeding E2 resulted in 50–61% increase in body weight compared with the control. Oestradiol‐17β and phytooestrogens both elevated significantly the percentage of females in the population. Feeding E2 at 20 mg kg?1 feed resulted in 70% females, while lower concentration of E2 (2 mg kg?1) resulted in only 30% after 100 days (Experiment 1). The same dose given for 150 days (Experiment 2) resulted in 88% females, indicating that both, the concentration and duration of E2 treatments had a significant effect on sex differentiation. Fish fed genistein at 2 mg kg?1 for 100 days, resulted in 55% of females, but at a higher dose of 20 mg kg?1 there were only 15% females. These results demonstrate that phytooestrogens can be used as alternatives to gonadal steroids for sex manipulation in eels, but the optimal concentrations and duration are still to be determined.  相似文献   

18.
以半滑舌鳎皮肤溃疡病的致病菌灿烂弧菌Vibrio splendidus和哈维氏弧菌Vibrio harveyi为指示菌,研究了循环水养殖系统各环节中细菌分布和消除工艺。结果表明,不健康的苗种携带病原菌进入养殖系统后,可分布在残饵、池壁污物、养殖工具及循环水各处理环节。而弧形筛过滤、曝气池气升、紫外线消毒是循环水养殖系统消除细菌的三大环节。用5×10-6 mol/L的KMnO4溶液浸泡工具2h,对细菌的杀灭率达到100%;用25×10-6 mol/L的KMnO4溶液擦拭养殖池壁污物1.5min后,细菌杀灭率高于90%;用100×10-6 mol/L浓度的H2O2溶液对养殖舌鳎病鱼进行药浴消毒处理10min,对体表细菌的杀灭率达到了94.49%。对鲆鲽鱼类循环水养殖系统中细菌的分布和消除效果进行了系统研究,研究结果可为建立循环水健康养殖工艺提供理论数据和参考。  相似文献   

19.
Land-based Atlantic salmon, Salmo salar, grow-out facilities utilize depuration to remediate off-flavor. Water used in this process is either discharged or repurposed as supply water in recirculating aquaculture systems (RAS). Both approaches require an understanding of water quality and waste production for water treatment decisions and compliance with pollution discharge standards; however, these data were lacking. Therefore, a study was carried out to characterize these parameters. To begin, 311 salmon (5–6 kg) originally cultured in freshwater RAS were stocked at 100 kg/m3 in an 18 m3 depuration tank. Feed was withheld 1 day before transfer and throughout the 7-day study period. Hours after stocking, total suspended solids (TSS), total phosphorus (TP), and total ammonia nitrogen (TAN) levels spiked, and concentrations declined thereafter. Delta TSS and TP were negligible by the end of the trial; however, TAN plateaued, indicating that salmon began to catabolize somatic tissue in the absence of feeding. Geosmin and 2-methylisoboreol levels in water and fish were low throughout the study. This research indicates that residual waste production occurs while depurating Atlantic salmon. Procedural refinements and recommendations were gleaned including locality for introducing depuration system water within RAS and extension of the feed withholding period before depuration.  相似文献   

20.
黄文华 《福建水产》2013,(5):386-390
采用分级微生物净化、曝气增氧、有效控温等循环水养殖系统对菲律宾鳗鲡进行苗种培育试验.鳗苗放养密度为3 000尾/m2和3 050尾/m2,约为传统模式的5～6倍.试验结果显示：在水温27～30℃范围内,对个体体重0.15～0.20 g（平均0.17g）的菲律宾鳗鲡苗进行培育,经过71d培育,个体平均体重为2.95 g,增重17.7倍,日均增加重量0.04g,鳗苗养殖成活率达到98.81％,高于传统养殖模式,水蚯蚓饲料系数7.14.试验表明,工厂化循环水养殖系统适用于菲律宾鳗苗培育,并具有节能减排优点,为开发新的鳗鲡养殖品种及环境友好型的鳗鲡育苗模式提供参考.  相似文献   

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