Use of decapsulated Artemia cysts in ornamental fish culture

Two series of feeding experiments were conducted to study the feasibility of using decapsulated Artemia cysts for direct feeding to ornamental fish. The first series evaluated the dietary values of the dried and the brine decapsulated Artemia cysts against two conventional live feeds, Artemia nauplii and Moina for adults and fry of the guppy, Poecilia reticulata Peters. In the second series, brine cysts were used for feeding to fry of four other important ornamental fish species, viz. platy, Xiphophorus maculatus (Günther), swordtail, X. helleri (Heckel), molly, P. sphenops Cuvier & Valenciennes and black neon tetra, Hyphessobrycon herbertaxelrodi Géry, and the results were compared with those fed Moina. Evaluation of the performance of the fish fed the various diets was based on stress resistance, growth and survival of the fish. Our findings indicated that decapsulated cysts could be used as a substitute for Artemia nauplii or Moina in freshwater ornamental fish culture. Apart from being a hygienic off‐the‐shelf feed, the direct use of the cysts also signifies a new area of application for low‐hatch cysts in the ornamental fish industry, with concomitant saving in feed costs.     

Identification of conditions underlying production of geosmin and 2-methylisoborneol in a recirculating system

Geosmin and 2-methylisoborneol (MIB) are semi-volatile terpenoid compounds produced as secondary metabolites by benthic and planktonic cyanobacteria, several genera of fungi, and various actinomycetes. These off-flavor compounds pose a heavy economic burden in the aquaculture industry rendering fish unmarketable unless purified by purging with large quantities of clean water. In the present study, the presence of off-flavor compounds was examined in a recirculating aquaculture system (RAS) for tilapia culture. In this zero-discharge system, where water from the fish basins is recirculated through parallel aerobic (drum filter and a trickling filter) and anaerobic treatment loops (sedimentation/digestion basin), concentrations of geosmin and, in particular, MIB were highest in the aerobic treatment loop. Lowest concentrations were detected in the anaerobic treatment loop. This latter finding pointed toward a possible reduction of these compounds in this basin. Two bacterial strains of the streptomycetes family were isolated from the aerobic, organic-rich, drum filter and the nitrifying trickling filter. In vitro tests with these isolates, closely related to Streptomyces roseoflavus and Streptomyces thermocarboxydus, revealed that MIB production exceeded geosmin production under all conditions tested and was significantly higher under aerobic than under anoxic conditions. Under the latter conditions, with nitrate as an electron donor, the S. roseoflavus-like isolate was capable of denitrification. Based on the results obtained in this study, it was concluded that aerobic, organic-rich conditions stimulate the growth of actinomycetes and subsequent production of geosmin and MIB in the system. The observed reduction of these compounds in the anaerobic water treatment component may serve in designing treatment steps aimed at alleviating the problem of geosmin and MIB accumulation in recirculating systems.     

Rates of fish waste production and effluent discharge from a recirculating system (biofish) under commercial conditions

Application of the regulatory principle of ‘best available technology’ (BAT) to fish farm effluent control has, to some extent, been a driving force for the development of new culture and treatment technology. In Norway today, there are a number of farms for the production of Atlantic salmon, Salmo salar L., smolts and brown trout, Salmo trutta L., fingerlings that utilize microstrainers for the removal of particles from the effluent water. At least one commercial farm also utilizes a simplified recirculation system called BIOFISH as a demonstration of new and alternative technology for the production of brown trout restocking fish. In this paper, calculated effluent discharge and rates of waste production from the biofish demostration trials are compared to literature data and to measurements on un-treated as well as microstrained effluents from the production of Atlantic salmon smolts in a traditional flow-through tank system. Rates of fish waste production in the biofish trials were obtained from mass-balance calculations based on measured concentrations of water quality parameters at several points in the system. The results of these calculations show fish waste production rates that are low, but comparable to data found in the literature. Given the level of waste treatment that takes place in the biofish tanks, the specific effluent discharge levels from those tanks, in terms of grams per kilogram biomass and grams per kilogram feed, are considerably lower than those found for salmon smolt production in traditional flow-through tanks. There are also substantial differences in hydraulic self-cleaning properties of the two systems and a corresponding difference in the distribution of effluent discharge during normal tank operation and during tank/effluent pipeline flushing. The results presented here give valuable information related to: (1) waste output characterization; (2) the long-term efficiency of commercially available particle separation systems; and (3) the capabilities of the simplified biofish recirculation technology under field conditions.     

浮球式生物滤器在鲟鱼工厂化养殖生产中的应用

本介绍了双层浮球式生物滤器在封闭循环式鲟鱼养殖生产中的应用情况。在一个120m^3水体,养殖密度19kg／m^3的鲟鱼循环养殖系统中,应用一套动力为4kw、处理能力为40T／h的BAF-40型双层浮球生物过滤设备进行养殖水体的循环使用处理。在生产过程中,对养殖水体的pH、DO、COD、悬浮物、氨氮、亚硝酸盐、硝酸盐等水化学指标进行了监测,并对鲟鱼在养殖过程中不同阶段的生长情况进行了测量。结果表明,在水体循环周期为1次／3h,换水周期为1次／周的条件下COD≤15mg／l、氨氮≤1mg／l、亚硝酸盐≤0．13mg／l、硝酸盐≤24mg/l,经12月养殖,成活率为98％,增重10倍。应用表明BAF-40型双层浮球式生物滤器可完全满足鲟鱼工厂化养殖生产的要求,确保鲟鱼养殖水体的水质和鱼类生长环境,达到良好养殖效果。     

工厂化循环水养殖预排污系统与排水系统研究与设计

一种新型的用于工厂化养殖固体颗粒预去除系统研制成功.该水处理系统最大的特点是:不需要任何的外在动力.该系统主要包括两部分:(1)靠养鱼池外置竖管设定水位来实现自动排水的排水系统;(2)靠养鱼池排水管口附近放置的筛网和转动水轮上的毛刷的共同作用,去除养殖循环水中的较大的固体颗粒(残饵和粪便)的排污系统.在去除过程中,耗水率均在5%以内;固体颗粒的去除率也均在80%以上.     

Performance of a recirculating fish production system stocked with tilapia hybrids

To demonstrate whether practical quantities of food fish could be produced in an inexpensive closed system suitable for family-scale use, 424 tilapia hybrid fry weighing a total of 177 g were stocked on 8 May 1981 into a 7600-liter (10·7 m²) steel-walled, vinyl-lined pool equipped with a rotating biological contactor, a settling basin, supplemental aeration and a passive solar collector. Ammonia, nitrite, nitrate, oxygen, temperature, pH and turbidity were monitored. New water was added at intervals during the experiment, at an average rate equivalent to 4% per day. Floating catfish chow was fed. To establish a growth curve and biomass estimate, 30 fish were removed, weighed and restocked every two weeks. After 146 days of grow-out, 48·6 kg of fish were harvested. Food conversion was 1·25:1. With suitable temperatures, 2·5 crops totaling at least 121 kg could be produced at a rate equal to 121000 kg/ha/yr of water surface.     

Design and performance of a recirculating aquaculture system for oyster larval culture

The major objective of this study was to introduce a newly designed recirculating aquaculture system (RAS) for oyster (Crassostrea angulata) larval culture. The system includes a culture tank, a suspended circular inlet‐pipe, an upwelling aeration pipe, combined “banjo” sieves and a bioreactor chamber containing microalgae life keeping installation. The system was designed to resolve three problems: (i) stranding of larvae caused by water level changes and aeration, (ii) physical clogging of the screens and also (iii) deterioration of diet microalgae. The culture tank, “banjo” sieve size, water flow rate and light intensity for maintaining microalgae activity were all designed according to the pattern of larval movement and feeding behaviour. Results of this study showed the best average SGR for larval length was 6.36%/d (9.5 μm/d) and survival rate was 80%, with initial rearing density of 50 larvae/ml, indicating the problems above were fully resolved. Consequently, the system is fit for larval culture in mass production of oysters.     

闭合循环水产养殖系统生产过程中生物过滤器功能的形成

生物过滤器对维持闭合循环水产养殖系统水质稳定起着核心的作用。生物过滤器存使用之前需要对生物膜进行培养、驯化,使生物过滤器有充分的硝化能力。生物过滤器硝化功能的建立一般需要较长的时间,淡水需要14～20d海水需要40～80d。在生产中因会产生较高浓度的氨氮、亚硝酸氮对饲养对象产生不良影响,增加养殖风险。     

Growth of tiger puffer Takifugu rubripes in closed recirculating culture system

ABSTRACT:   Two feeding experiments were conducted to elucidate growth performance of tiger puffer in a 10 m³ water volume closed system. In experiment 1, 1000 fish of 3.5 g average body weight were fed tiger puffer commercial feed twice daily to apparent satiation, 6 days a week for 224 days. Sand-filtered sea water was used and no water was exchanged during the rearing period. Immediately after cutting of lower teeth at day 112, daily feed consumption decreased greatly and 60 fish died in few days. Feeding rates recovered and then decreased gradually as nitrate levels increased from 600–1048 mg N/L. Fish grew to 343 g with 91% survival rate and 87% feed efficiency. Rearing conditions of experiment 2 were similar to experiment 1, except that culture water was exchanged to maintain the nitrate level less than 600 mg N/L during the 224-day experiment. Mortality and reduction of feed consumption occurred immediately after teeth cutting as was observed in experiment 1. Significant reduction of feed intake was not found during other rearing periods. Fish of 3 g grew to 303 g with 91% survival rate and 72% feed efficiency.     

Diel rhythms of oxygen consumption rates of California halibut (Paralichthys californicus) under culture in a recirculating system

Diel oxygen consumption patterns were determined in this study for California halibut (Paralichthys californicus) 3.2, 4.4, 6.2, 7.5, 9.2, 11.8, 12.8 and 14.2 g and between 110.5, 113.8, 115.7, 117.9, 120.1, 126.5, 132.4, 140.6, and 165.6 g held under farm-like conditions. The concept farm-like refers to a fish rearing condition as close as possible to a farming operation in terms of density, loading, and daily management. Open respirometries were performed in culture raceways during 24 h cycles while fish were growing from 3.2 g up to 165.6 g to determine hourly oxygen consumption rates by mass balance calculations. Fish were offered feed continuously during 12 h (within the 16 h light phase) resulting in maximum daily oxygen consumption rates that were between 1.2 and 1.5 times the mean daily values. A typical diel oxygen consumption pattern of the smaller group of fish tested (range between 3.2 and 14.2 g) had a peak during the feeding period, and relatively low and falling oxygen consumption after feeding was stopped. Oxygen consumption of the larger group of fish (range between 110.5 and 165.6 g) showed a less marked diel variation and did not change significantly after feed was distributed. In conclusion, diel oxygen consumption rates for California halibut reported here are key bioengineering parameters to be used when designing and sizing a rearing facility for the intensive culture of California halibut.     

Hatching events in the cysts of Artemia salina

Prior to hydration, the cysts of Artemia salina are cup-shaped with a diameter of approximately 0.18 mm. Upon immersion in sea water, the cysts slightly increase in diameter to 0.19 mm and assume a spherical shape. Hatching begins with the splitting of the surface coat. The split runs along a straight line, approximately one-half the circumference of the cyst. The exposed fracture in the surface coat reveals three distinct regions: (1) a thin (1.2 μm) smooth outer layer; (2) a thick (4.7 μm) ‘spongy’ layer; and (3) a thin (1.8 μm) fibrous inner layer. The split becomes more pronounced as the nauplius, enclosed within a transparent hatching membrane, slowly emerges. Once completely emerged from the cyst, the nauplius begins a series of beating movements which rupture the hatching membrane, allowing the nauplius to swim free.     

封闭循环流水养殖的花鳗鲡脂肪酸特征分析

为探寻封闭循环流水养殖模式下养殖的较大型(≥2 kg)花鳗鲡(Anguilla marmorata)各可食部的脂肪酸特征,利用索氏抽提法获得各部位的粗脂肪,以37种脂肪酸甲酯混标标准品为标准,气相色谱外标法检测脂肪酸的组成。检测结果显示,鱼皮中粗脂肪含量最高为26.96%,鱼肉的粗脂肪含量为10.36%;不同可食部的脂肪酸组成基本相似,饱和脂肪酸9种,单不饱和脂肪酸6种,多不饱和脂肪酸8种,饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸间的比例大约都为1∶3∶1,三大类脂肪酸中含量最高的分别为软脂酸C16∶0、油酸C18∶1n9c和二十二碳六烯酸C22∶6n3,油酸在不同可食部中均超过20 g/100 g总脂,C22∶6n3(DHA)在不同可食部中含量在4.42~5.59 g/100 g总脂之间。研究表明,较大型花鳗鲡是人体所需脂肪酸的良好食物来源。     

Performance of a commercial recirculating alligator production system employing a paddle-washed floating bead filter

A 2.83 m³ prototype paddle-washed bead filter for combined solids capture and biological filtration was successfully operated in a commercial recirculating alligator (Alligator mississippiensis) facility. The bead filter was originally designed and operated as a downflow filter but due to operational and water quality problems, it was reconfigured to operate in an upflow mode. Water quality conditions and filter performance improved dramatically, with the upflow bead filter capable of handling the equivalent loading of 10.3 kg m⁻³ beads per day of 40% protein feed, despite oxygen limitations and hydraulic problems associated with the retrofitted alligator system.     

Artemia salina as pabulum for growing Penaeids under laboratory conditions

Growing interest in Artemia salina Leach is supported by its high protein content, the relative ease of its mass production, and its incompletely utilized potential biomass which is found in saltpans all over the world.Experiments involving the catching of adult brine shrimps by means of a 500 μm nylon net located on the main outflow canal were carried out in Margherita di Savoia saltworks in southeastern Italy preliminarily in August 1980. Replicates during May–July 1981 showed it was possible to collect about 250 g min^?1 of adult Artemia. According to the figures of the samples taken, it is reasonable to assume a brine shrimp standing crop of at least 50 tonnes (wet weight) over a 1000 ha surface area. The Artemia collected in this way were tested for feeding Penaeids under laboratory conditions, as sole food and as supplement to a dry selfmade diet. Firstly Penaeid growth supported by mussels was tested in comparison with frozen Artemia diet. The latter gave the best results with 30% daily supply of shrimp body (wet weight). Moreover Artemia were tested as a balancing component of a dry diet to correct a deficit of aminoacids and supply missing highly unsaturated fatty acids (HUFA).With this mixed diet it was enough to supply A. salina 2 days per week to achieve promising results which are considered a good compromise between economics and the growth rate of Penaeus japonicus Bate. Consequently, it is suggested that intensive and/or extensive Penaeid cultures be planted near saltpans, utilizing brine shrimp biomass as a food source which could otherwise be wasted.     

工厂化水产养殖中的自动控制技术

本文从工厂化水产养殖自动控制系统的组成、自动控制方法、自动控制技术在水质参数检测与调控中的应用等方面,论述了有关研究的技术成果和未来发展趋势.根据水产养殖工业化和自动化发展,以及自动控制技术在水产养殖中的广阔应用前景,指出了发展水产养殖自动化检测和调控精准技术的必要性,提出发展规范化、标准化的水产养殖自动化技术,以推动...     

工厂化水产养殖中的自动控制技术

本文从工厂化水产养殖自动控制系统的组成、自动控制方法、自动控制技术在水质参数检测与调控中的应用等方面,论述了有关研究的技术成果和未来发展趋势。根据水产养殖工业化和自动化发展,以及自动控制技术在水产养殖中的广阔应用前景,指出了发展水产养殖自动化检测和调控精准技术的必要性,提出发展规范化、标准化的水产养殖自动化技术,以推动水产养殖工业化的发展。     

循环水抽屉式立体养殖系统养殖马粪海胆研究

研究利用循环水养殖设备和多层抽屉式养殖箱构建一种新型的立体循环水养殖系统,对马粪海胆进行为期90 d的养殖试验.试验结果表明,养殖用水在循环使用的情况下,水质指标处于良好状态:NH+4-N为0.02～0.15 mg/L,NO-2-N为0.01～0.35 mg/L,pH值为7.7～8.2;马粪海胆养殖密度可达1 444.23 g/屉(约20 L),特定生长率(SGR)为0.33,成活率为89.15%.     

花鳗鲡工厂化循环水高密度养殖模式初探

根据花鳗鲡(Anguilla marmorata)生理生态特点构建循环水养殖系统.系统集成了臭氧消毒杀菌、机械过滤、生物过滤、液氧增氧等关键技术.试验研究循环水养殖系统中花鳗鲡的生长情况,对试验期间各项水质指标动态变化进行了监测.结果表明:各项水质指标均保持在花鳗鲡生长适宜范围内;平均规格29.97 g的花鳗鲡经过260 d养殖,平均体重达到716.20 g,成活率达到86.5%,收获时鱼产量为82.6 kg/m3,饵料系数维持在1.25左右,养殖周期较传统养殖模式缩短4～5个月,日换水率约为3%.利用封闭式循环水养殖模式进行花鳗鲡养殖切实可行.