细菌在鱼池生态系统中的作用

细菌在池塘养鱼生态系统中具有极为重要的作用。 1.细菌是池塘鱼类幼鱼的主要饵料,更是滤食性和杂食性鱼类的终生饵料。池塘中有50％的细菌可以为滤食性和杂食性鱼类所利用。这些细菌含有容易消化的蛋白质、碳水化合物和其它营养物质,它们的蛋白质含     

如何提高化肥养鱼效率

1 化肥养鱼的原理与特点,化肥养鱼的原理可以简单地概括为：通过施肥向水体补充营养物质,促进浮游植物大量繁殖,并使水生维管束植物、固着生物、自养性细菌等数量增加。在满足滤食性鱼类摄食的同时,也为吃食性鱼类提供部分食料。化肥养鱼具有肥效快,利用率高,操作简便。投工量少。便于机械化作业,成本低,效益好等特点。很多发达国家采用化肥养鱼,如美国用化肥养罗非鱼和太阳鱼;     

海湾扇贝对网箱养鱼有机废物的利用效率研究

采用模拟流水系统,研究了海湾扇贝对三角褐指藻、配合饲料、鱼类粪便3种不同饵料的滤水率、摄食率、吸收效率。结果表明：海湾扇贝对3种饵料的吸收效率分别为73．78±2．30（％）、63．424±1．23（％）、67．79±0．64（％）。研究认为,海湾扇贝能够有效地利用鱼类网箱养殖过程中产生的有机废物,开展滤食性贝类和鱼类的合理混养可有效减轻环境污染。     

工厂余热水养殖红罗非鱼食性的分析

通过显微镜检查胃、肠内容物,可以确定红罗非鱼是一种食谱很广的杂食性鱼类。红罗非鱼鱼苗阶段主要以有机碎屑、虫卵、枝角类和藻类为食,而人工饵料的出现次数百分比仅占6.2％;幼鱼阶段主要以有机碎屑、人工饵料、藻类和轮虫为食,食性已转化为小型浮游生物为主;成鱼阶段主要以人工饵料和有机碎屑为食。红罗非鱼能充分利用天然饵料,这对降低生产成本,有很大意义。     

纯化水库渔业资源现状及利用对策

库水总盐量约为0.6mg／L，属一般淡水，平均总碱度、总硬度均有利于水生生物的生长发育。浮游植物平均数量474．23万个／L,生物量4．608mg／L，作为滤食性鱼类优质饵料的硅藻门在数量和生物量上占绝对优势。浮游动物平均生物量0．828mg／L，平均数量2498 ／L，属一般营养水平。底栖动物生物量0．663g／m^2，种类组成简单，数量较少，生物量较小，所能提供的鱼产力较低。针对该水库的渔业资源现状，提出了合理的利用方式。     

用人工配合饵料驯化黑龙江鲟稚鱼转口的试验

黑龙江省鲟鱼属偏肉食性的杂食性鱼类。在自然水域中,幼小个体主要摄食底栖生物和水生昆虫,成鱼除索食这些生物外,还食小型鱼类、虾类。随着鲟鱼增养殖业的兴起,人工养殖鲟鱼面临的问题之一即饵料。因生物饵料来源不足且成本较高,将在很大程度上限制鲟鱼业的发展。探索改变鲟鱼食性的可能性使其由食生物饵料为人工配合饵料即是本试验的主要目的。 一、材料和方法 试验用的人工配合饵料系通过对苏联鲟鱼和日本鲑鱼饵料配方对比及黑龙江鲟鱼食性的研究制定出3组配     

亿龙生化肥料系列产品概述

任何一种鱼肥,当施放到养殖水体以后,都是通过肥料所含的各种营养元素作用于水生植物(水体中主要是浮游植物,也称藻类)来提高水体的初级生产力。藻类既可以直接作为白鲢等滤食性鱼类的饵料,同时也是水中浮游动物和其它微型动物的饵料,最终通过食物链被池塘中的经济水生生物——     

高档水产养殖新品种介绍

1 匙吻鲟 　　匙吻鲟是北美(美国)产的一种名优大型的淡水经济鱼类,食性类似我国的鳙鱼,以浮游动物为饵料,属滤食性鱼类,但也能摄食水蚯蚓和人工配合饲料.……     

雌性化尼奥罗非鱼海水池塘养殖试验

子一代尼奥雄性化罗非鱼除具有食性广泛、适应性强、生长快等罗非鱼一般化点外,还有抗逆性强、品质好等特殊性状,是优良的淡水养殖品种。现将其海水池塘养殖技术报告如下：l试验条件1．1池塘为本场对虾养殖池塘,长方形,长120m,宽72m,面积13亩。其池底为硬泥,四周有一条宽3m、深4Ocm的环水沟。池塘平均水深1．3m,进排水方便,有提水设备。1．2鱼苗取自本场用海水繁殖的尼罗罗非鱼（雌性）与奥利亚罗非鱼雌性）杂交的子一代尼奥罗非鱼苗,雄性率为gO％,鱼苗平均体长为2．0～45cmo1．3饵料自制的配合饵料、杂鱼虾等。配合饵料的配方…     

沙滩防渗池高产养鱼配套技术研究

利用沙滩塑膜防渗鱼池１１２亩，采取主养吃食性鱼类，混养滤食性鱼类，套置小型网箱单养罗非鱼，投喂人工配合颗粒饲料等综合配套技术措施，总产鱼１３１４９９．２ｋｇ，平均亩产１１７４．１ｋｇ，其中网箱单产１１８．ｇｋｇ／ｍ３，经专家鉴定认为：其技术和经济效益达到国内先进水平。     

Culture of organic tilapia to market size in periphyton‐based ponds with reduced feed inputs

In fish production under organic standards, only organic feeds and manures can be supplied. The cost of organic pelleted feeds is twice that of regular feeds. To support the organic production of hybrid tilapia [Oreochromis niloticus (L.) ×Oreochromis aureus (Steindachner)], a series of experiments in earthen ponds, to improve natural food production for this fish while reducing costs of added feed, are in progress. To improve natural food production for tilapia, plastic substrates equivalent to 50% of the pond surface were introduced into the water column to induce periphyton growth on them. To reduce costs, the feeding rate on pelleted feed was reduced to 60%. Tilapia growth in these periphyton ponds was then compared with ponds without underwater substrates that received the full feed rate. The polyculture consisted of 90% large (320 g stocking weight) hybrid tilapia and small amounts of other fish, at a total stocking density of 13 800 fish ha^?1, during 87 summer days. The results showed improved nitrification and the development of a large autotrophic periphyton biomass that competed with the phytoplankton in the periphyton ponds, and only a 10% and 15% reduction, respectively, in the tilapia daily and specific growth rates, with 40% feed saving. These results point towards periphyton‐based aquaculture as an appropriate technology for the reduction in production costs, allowing economically viable organic tilapia production.     

Influence of pond fertilization and feeding rate on growth performance, economic returns and water quality in a small-scale cage-cum-pond integrated system for production of Nile tilapia (Oreochromis niloticus L.)

The effects of pond fertilization and feeding rate on growth, economic returns and water quality were investigated to develop a low‐cost cage‐cum‐pond integrated system for production of Oreochromis niloticus (L.). Hand‐sexed male fingerlings averaging 19±0.39 and 32±0.69 g were stocked in cages and open ponds at 150 fish cage^?1 and 2 fish m^?2 respectively. Fish were cultured for 114 days in five triplicate treatments. Cages were installed into ponds and caged fish were fed a 24% protein diet at 3% (T1) and 6% (T2) body weight day^?1 (BWD) without pond fertilization, and 6% BWD with pond fertilization (T3). The open water in the fourth treatment (T4) was not stocked but contained caged fish, which were fed 6% BWD for the first 57 days followed by 3% BWD for the remaining period. Ponds in the control (T5) had no cages and were neither fertilized nor open‐pond fish fed. Feeding rate and pond fertilization significantly (P<0.05) affected fish growth, profitability and water quality among treatments. Fish growth, feed utilization, fish yield, water quality and profits were significantly (P<0.05) better in T3 than the other treatments. It was concluded that fish production and economic returns were optimized at 6% BWD in fertilized ponds.     

The effect of stocking different ratios of common carp, Cyprinus carpio L., and tilapias in polyculture ponds on production characteristics and profitability

Production characteristics and profitability of three carp-tilapia stocking ratios (1:1, 1:2 and 1:5) were compared in a semi-intensive polyculture system. The. experiment was carried out at the same total stocking density of 1 fish m², in nine 1000-m² earthen ponds. Common carp, Cyprinus carpio L., and a tilapia hybrid, Oreochromis niloticus (L.) x 0. aureus (Steindachner), were stocked at a joint density of 900 fish per pond, while grass carp, Ctenopharyngodon idella (Cuvier & Valenciennes), and silver carp, Hypophthalmichthys molitrix (Valenciennes), were each stocked at 50 fish per pond in all treatments. Mean harvested weights of both common carp and the tilapia hybrid were markedly decreased upon the increase in density of their own species. Survival of all four species was over 80% in all three carp-tilapia stocking ratios. The differences in relative profitability of the three carp-tilapia stocking ratios did not exceed 10% on the basis of 1991 prices. However, based on 1994 prices, relative profitability of the 1:2, and particularly, the 1:5 carp-tilapia stocking ratio were 35% and 41% higher than the 1:1 ratio, respectively. This was because of the increase in the price of large carp and tilapia of all sizes, and a decreases in the price of small carp.     

Evaluation of Nile tilapia pond management strategies in Egypt

Five pond management strategies for Nile tilapia Oreochromis niloticus L. production were evaluated in 0.1‐ha earthen ponds in Egypt during a 145‐day production cycle. Pond management strategies developed by the Pond Dynamics/Aquaculture Collaborative Research Support Programme (PD/A CRSP) were compared with a traditional and a modified Egyptian pond management strategy. Young‐of‐year Nile (mixed‐sex or sex‐reversed) tilapia were stocked into ponds at 20 000 fish ha^?1. Sex‐reversed tilapia were stocked into chemical fertilization, organic fertilization plus formulated feed and feed only treatment ponds, whereas mixed‐sex tilapia were stocked into organic fertilization plus formulated feed and chemical plus organic fertilization plus formulated feed treatment ponds. Nile tilapia yields ranged from 1274 to 2929 kg ha^?1. Nile tilapia yields in organic fertilization plus formulated feed treatments were significantly greater than the yield from chemical fertilization ponds. PD/A CRSP pond management strategies did not produce significantly greater Nile tilapia yields than the traditional Egyptian system, but a larger percentage of harvested tilapia in the organic fertilization plus feed treatments were classified in the first and second class size categories compared with the traditional Egyptian system. Organic fertilization plus formulated feed pond management strategies had the highest net returns, average rate of return on capital and the highest margin between average price and break‐even prices to cover total variable costs or total costs.     

Diet supplemented with probiotic for Nile tilapia in polyculture system with marine shrimp

The aim of this study was to assess the effect of a probiotic (Lactobacillus plantarum) supplemented diet on Nile tilapia (Oreochromis niloticus) in a polyculture system with marine shrimp (Litopenaeus vannamei) as regards culture performance, hematology, and gut bacterial microbiota. Ten 20-m2 pens were arranged in one earthen pond and stocked with 2 fish (41.9 g) m⁻² and 10 shrimp (2.3 g) m⁻², in total of 40 Nile tilapias and 200 shrimp per experimental unit. Tilapia groups in five of the experimental units were fed a commercial diet supplemented with L. plantarum and the other five with an unsupplemented commercial diet (control). After 12 weeks of culture, the tilapia groups fed the probiotic-supplemented diet presented values 13.6, 7.5, and 7.1% higher for feed efficiency, yield, and final weight, respectively. Viable culturable heterotrophic bacteria counts were reduced, and the number of lactic acid bacteria was increased in the gut of fish and shrimp fed the probiotic-supplemented diet. Hematological analyses showed higher number of thrombocytes and leukocytes in tilapia fed the supplemented diet. L. plantarum utilized in this study colonized the gut of tilapia and shrimp and resulted in reduced number of total bacteria and increased tilapia final weight and feed efficiency.     

Growth, Survival, and Body Composition of Cage-Cultured Nile Tilapia Oreochromis niloticus Fed Pelleted and Unpelleted Distillers Grains with Solubles in Polyculture with Freshwater Prawn Macrobrachium rosenbergii

Abstract.— A 12‐wk feeding trial was conducted in cages with juvenile Nile tilapia Oreochromis niloticus to evaluate distillers grains with solubles (DDGS) as a direct feed, the effects of pelleting on its utilization, and the compatibility of caged tilapia and prawns in polyculture. Nine 1.0‐m³ cages were stocked with 200 juvenile (26 ± 0.9 g) tilapia. Cages were suspended in a 0.2‐ha pond stocked with juvenile freshwater prawns Macrobrachium rosenbergii at 40,000/ha. Three replicate cages were randomly assigned to each dietary treatment. In one dietary treatment DDGS was fed as an unpelleted loose grain ration (26% protein). In a second dietary treatment fish were fed DDGS that had been steam‐pelleted (23% protein). Fish in a third dietary treatment were fed a commercial catfish diet (31% protein) for comparison. After 12 wk, individual weight, individual length, and specific growth rate were significantly higher (P < 0.05) and feed conversion ratio was significantly lower (P < 0.05) for fish fed the commercial catfish diet than for fish fed either unpelleted or pelleted DDGS. Specific growth rate was significantly higher (P < 0.05) for fish fed pelleted DDGS than for fish fed unpelleted DDGS. Survival did not differ significantly (P > 0.05) among treatments (>95%). Although growth was increased in fish fed the commercial diet, their cost of production (<0.66/kg gain) was significantly higher (P < 0.05) than in fish fed unpelleted and pelleted DDGS (<0.26/ kg gain and <0.37/kg gain, respectively). The costs of gain in fish fed unpelleted DDGS was significantly lower (P < 0.05) than in fish fed the pelleted DDGS. Prawn production was 1,449 kg/ha and addition of tilapia in polyculture increased total pond productivity approximately 81 %. These data suggest that DDGS provides economical growth in tilapia when fed as a direct feed and that polyculture of tilapia may improve overall pond efficiency in freshwater prawn production ponds, even at temperate latitudes.     

Response of Nile tilapia (Oreochromis niloticus) to diet acidification: Effect on growth performance and feed utilization

A 12-week feeding trial was undertaken to assess growth, nutrient utilization, some hematological parameters, and proximate composition of Nile tilapia (Oreochromis niloticus) fed diets supplemented with graded levels (0.5%, 1.0%, and 1.5%) of two blends of organic acids or organic salts. Seven isonitrogenous (300 g CP kg^?1) and isocaloric (19.0 MJ gross energy kg^?1) diets were formulated. The control diet (D1) contained neither added blend of organic acids nor organic salts. Three diets (D2, D3, and D4) were supplemented with 0.5%, 1.0%, and 1.5% of malic acid + oxalic acid blend (OAB), respectively. The other three diets (D5, D6, and D7) were supplemented with 0.5%, 1.5%, and 1.5% of calcium lactate + sodium acetate blend (OSB), respectively. Fingerlings (7.05 ± 0.02 g) were randomly distributed into 21 glass aquaria (160 liter), with each aquarium holding 15 fish. At the end of the feeding trial, O. niloticus offered the control diet showed lower growth and feed utilization than all those fed the organic acids or organic salts blends supplemented diets. Fish fed the diet D3 showed the highest body weight (BW), body length (BL), weight gain (WG), specific growth rate (SGR), feed intake (FI), and the best feed conversion ratio (FCR) and protein efficiency ratio (PER). Fish fed diet supplemented by 1.5% OAB (D4) showed the highest serum protein content, while control group (D1) showed the lower level of total lipids compared with the other treatments. Fish group fed the diet supplemented with 0.5% of OSB (D5) showed the highest protein and ash contents and the lowest lipid content of the whole fish body, while the control group showed the lowest protein and the highest fat content. The present observations suggest that the growth, feed utilization, and health status of juvenile O. niloticus can be enhanced with a supplementation of 1% of OAB or OSB in the diet.     

Effects of pond depth and water temperature on the growth, mortality and body composition of Nile tilapia, Oreochromis niloticus (L.)

The effects of varying water depths and temperature on the growth, feed utilization, mortality rates and body composition of Nile tilapia, Oreochromis niloticus (L.), were evaluated. Triplicate groups of 20 fish (mixed-sex) m^-3 were stocked into 200-m² freshwater earthen ponds maintaining four water depths: 50, 100, 200 and 300 cm. The fish were fed on commercial fish pellets (23% protein), twice a day for 10 months (May 1991-February 1992). Water temperatures ranged from 5 ^oC to 33 ^oC. Growth performance and survival were significantly affected by pond depth and water temperature. Fish weight gain was lowest (250 g per fish), feed conversion poorest (3.15), and mortality highest (41.5%) at 50 cm depth, whereas 100-200 cm depth produced the best growth rates at warm water temperatures (> 21 ^oC). At 100-200 cm depth, weight gain was significantly (P<0.001) increased to 348-362 g per fish, feed conversion improved to 2.53-2.59 (P<0.01) and mortality reduced to 21-27% (P<0.001). Fish growth was significantly reduced (P<0.001) below 21 ^oC. Below 10 ^oC, fish stopped feeding and developed severe stress, fungal infection and high mortality. However, mortality rate was significantly reduced at 300 cm depth. Body lipid and protein were sharply decreased (P<0.001) with decreasing water temperature and pond depth, whereas body ash showed irregular patterns.     

Partial substitution of fish meal with soybean and cottonseed meals in diets for African bonytongue,Heterotis niloticus (Cuvier, 1829) fingerlings: effects on growth,feed efficiency and body composition

A feeding trial was conducted to examine the suitability of soybean meal (SBM) and cottonseed meal (CSM) as a partial substitute for the dietary protein supplied by fish meal for H. niloticus fingerlings. Fish were fed with four isonitrogenous (350 g kg^?1 crude protein) and isoenergetic (18.8 kJ g^?1 GE) diets in which fish meal protein was gradually replaced by plant protein from a mixture of SBM and CSM (0%, 25%, 50% and 75% in diets 1, 2, 3 and 4 respectively). Triplicate groups of fingerlings H. niloticus (mean weight of 5 g) were handfed twice daily to apparent satiation for 60 days inside net hapas. Growth performances (SGR varied from 3.09% to 3.16% day^?1) of fingerlings fed diets containing 0%, 25% and 50% plant protein were not significantly different (P>0.05). At 75% fish meal substitution, growth and feed utilization efficiency indicators were significantly reduced (P<0.05). The carcass composition were also significantly (P<0.05) affected by the replacement level of fish meal, except dry matter and ash. Results suggest that the dietary fish meal protein could efficiently be substituted by a mixture of soybean and cottonseed meals up to 50%, without adverse effects on maximal growth in practical diets for H. niloticus fingerlings.     

The Potential of Groundnut (Arachis hypogaea L.) By-Products as Alternative Protein Sources in the Diet of Nile Tilapia (Oreochromis niloticus)

The nutritional suitability and cost effectiveness of groundnut cake (GNC) and groundnut husk (GNH) as protein sources in the diet of Nile tilapia (Oreochromis niloticus), mean initial weight 4.24 ± 0.20 g, was evaluated over a 56-day growth period. Five isonitrogenous (320 gkg^?1), isolipidic (100 gkg^?1), and isoenergetic (18 KJg^?1) test diets were formulated in which GNC proteins replaced fish meal (FM) protein at levels of 25% and 50%, and GNH protein at 10% and 20%. The control diet had FM as the sole protein source. The growth experiment was conducted in plastic tanks in a recirculation system; each dietary treatment was in triplicate. After feeding fish at 4%–6% body weight per day, GNC and GNH protein replacements up to 50% and 20%, respectively, did not significantly (P < 0.05) affect growth and feed utilization. The study indicated that GNC and GNH protein could replace at least 50% and 20% of fish meal protein, respectively, in the diet of O. niloticus fingerlings without adversely affecting growth, feed efficiency, whole body composition, and nutrient digestibility. Generally the GN by-products-based diets were more cost-effective than the fish meal-based diet, particularly GNH replacing 20% fish meal protein.