国外简讯

大白姑鱼生长的最适盐度　　为测定盐度对大白姑仔稚鱼生长和成活的影响 ,进行了两次试验。第一次试验将 6日龄大白姑鱼苗分别放养在盐度为 5‰、1 2 .5‰、2 0‰、2 7.5‰、3 5‰的水体中养殖 1 4 d。发现大白姑鱼苗可在不同盐度中生长。根据生长速度和成活率 ,得出 6～ 2 0日龄鱼苗生长的最适水体盐度为5‰～ 1 2 .5‰。不同盐度水体中生长的大白姑鱼苗均不同程度地感染了腰鞭毛虫 ,但盐度为 5‰水中的鱼苗感染率最低 ,为 0 .2个 /尾。感染率随水体盐度提高到 2 0‰而提高 ,达3 3 .1个 /尾。而水体盐度继续提高至3 5‰ ,感染率则下降至 1 …     

光合细菌对罗非鱼鱼苗养殖水质及抗病力的影响

向罗非鱼鱼苗的养殖水体中投入光合细菌,研究不同浓度光合细菌对罗非鱼鱼苗养殖水体水质和鱼苗免疫力、成活率的影响.结果表明,水体中引入光合细菌浓度为4.5×102～4.5×106 cfu/mL时,各试验组的氨氮和亚硝酸盐氮含量都显著低于对照组(P<0.05);当浓度为4.5×104 cfu/mL时,罗非鱼鱼苗的抗病力增强,表现在鱼苗体内的组织过氧化物酶(POD)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)、溶菌酶(LSZ)和抗菌活力都显著高于对照组(P<0.05),罗非鱼鱼苗的存活率也提高了6.67%.适宜浓度的光合细菌,能有效改善鱼苗养殖水体的水质,提高鱼苗免疫力和成活率.     

不同浓度的枯草芽孢杆菌对罗非鱼鱼苗的养殖水体水质及其抗病力的影响

罗非鱼鱼苗的养殖水体中引入不同浓度的枯草芽孢杆菌,检测水体的水质指标、鱼苗体内与免疫相关酶的酶活力、鱼苗的生长率和成活率。实验结束时,引入1.0×10^4 cfu/mL枯草芽孢杆菌实验组,氨氮和亚硝酸盐氮含量分别为2.72 mg/L、0.15 mg/L,显著低于对照组（P〈0.05）;AKP活力、抗菌活力分别达249.9 U/g prot、0.59μg/mL,显著高于对照组（P〈0.05）;鱼苗成活率也显著高于对照组（P〈0.05）,比对照组提高了11.0%。结果显示：适合浓度的枯草芽孢杆菌能有效地改善鱼苗养殖水体的水质,提高机体免疫力和成活率。     

温度和密度对细鳞鲑苗种培育成活率的影响

在饵料构成完全相同,培育水温在适宜范围,日常管理方法完全一致的前提下,不同温度变化和密度对细鳞鲑苗种培育成活率存在差异。结果显示:在水温每天趋于恒定,放养密度为上浮仔鱼至体长2~2.5cm鱼苗,密度3万尾/m~3水体,鱼苗体长2.5~3.5cm,密度1.5万尾/m~3水体,3.5cm以上移入水泥池进行培养,密度1 000尾/m~2时,苗种培育成活率最高可达80%。     

斜带石斑鱼生态优化与病害防控育苗模式的研究

本文报道了斜带石斑鱼生态优化与病害防控育苗模式的研究,研究重点为如何预防神经坏死病毒（NNV）的感染,包括：1、阻断病毒的传播途径,选择不带病毒的受精卵,并在布卵前,对育苗池、用具以及生物饵料进行严格消毒.2、保持育苗池水小生态相对稳定,使水体中益生菌成为优势种群,消耗水体氨氮等有害物质,同时抑制水体里有害细菌的繁殖.3、进一步规范仔、稚、幼鱼期的饵料系列及其配制,保证鱼苗的营养以提高鱼苗的活力和健康水平,提高其抵抗病毒病侵袭的能力,从而提高鱼苗的成活率.     

生物饵料、放养密度及水体交换量对鲤鱼苗种生长的影响

为测定生物饵料量、合理放养密度及饲养过程中水体交换量对鲤鱼苗种生长的影响，共进行了为期四个月的生长实验。实验鱼苗平均长度10mm，下塘时除15号池生物饵料量较少外，其它三池均做到适时下塘。15号、8号池放养密度为600尾／m^2，18号、13号池放养密度为300尾／m^2。其中18号池的换水量较大。结果表明，人塘时生物饵料充足、按合理的放养密度放养、水体交换量大的池塘鱼苗生长快、体质壮、成活率高。相反则鱼苗生长慢、体质弱、成活率低。     

提高鱼苗下塘成活率的措施

<正> 1 清塘消毒 用生石灰等药物清塘,以杀死野杂鱼和敌害生物,提高鱼苗的成活率。清塘后,在鱼苗下塘前7d施基肥,用发酵后的鸡粪3000～4500kg/hm~2。一般施肥后5～7d,轮虫到达高峰期。2 掌握好下塘时间 鱼苗下塘时的适口饵料—轮虫,对鱼苗的成活率有很大影响。因此,轮虫繁殖     

黑鲪工厂化育苗技术研究

研究了亲鱼选择、暂养和苗种的饵料转换、日常管理和病害防治等一套工艺流程，在３００ｍ３育苗水体中，育出２６．７ｍｍ以上黑鲪鱼苗３２．１５万尾，鱼苗培育成活率３３．５％。专家鉴定认为，本成果总体达国内先进水平，其中产仔率、单位水体出苗量等方面属国内领先。     

长吻鮠鱼苗、鱼种培育技术的研究

本文对长吻鮠鱼苗鱼种培育技术作了初步研究。几年试验共育出鱼苗8万多尾，鱼种1万多尾。鱼苗经25～33天培育，平均全长4．8厘米，体重1．2～2．7克，成活率63．8～99．1％。水蚯蚓是鱼苗阶段的良好饵料，配合饲料也可使用。当年鱼种生长较快，一般体重41～74克，最好的可达90克以上。苗种生长适宜水温为24-28℃。     

黑Jun工厂化育苗技术研究

研究了亲鱼选择、暂养和苗种的饵料转换、日常管理和病害防治等一套工艺流程，在３００ｍ＾３育苗水体中，育出２６．７ｍｍ以上黑Ｊｕｎ鱼苗３２．１５万尾，鱼苗培育成活率３３．５％。专家鉴定认为，本成果总体达国内先进水平，其中产仔率、单位水体出苗量等方面属国内领先。     

地衣芽孢杆菌De在优质草鱼养殖中的应用研究

运用综合对比分析法探讨了地衣芽孢杆菌Bacillus licheniformis De在优质草鱼（Ctenopharyngodon idellus）养殖中的应用效果,其评价指标分别为成活率、水体pH、透明度、溶解氧及水中氨氮、硝酸盐浓度等。结果表明,施用地衣芽孢杆菌De可在一定程度上使水体环境和养殖生产性能得到优化,提高养殖草鱼的成活率,显著降低水体透明度及水中氨氮、硝酸盐含量（P〈0．05）,使水体pH、溶解氧有利于草鱼的生长。其中施菌组较对照组的成活率、水体pH、溶解氧分别提高了3．2％、3．9％、25．5％,而水体透明度、氨氮及亚硝氮浓度则分别降低了38．5％、74．6％、69．3％。     

淡水鱼鱼糜性质研究

采用清水漂洗、盐水漂洗和碱水漂洗、钙离子、热处理方法对草鱼、白鲢鱼糜进行试验,阐明诸因素对草鱼、白鲢鱼糜凝胶性能的影响,为生产鱼糜制品提供合理的工艺参数、研究表明,草鱼2次清水与1次盐水漂洗凝胶性能较好,鲢鱼鱼糜的最佳钙离子质量分数为0 5%。     

不同C/N对草鱼池生物絮团的形成及水质的影响研究

为了研究草鱼池生物絮团形成所需的适合C/N,实验分析不同C/N水平对水泥池中生物絮团的形成、水质及草鱼生长的影响。对照组投喂基础饲料(C/N为10.8∶1),实验组在基础饲料上添加葡萄糖,控制C/N分别为15∶1、20∶1和25∶1。结果显示,当C/N≥15时,形成的生物絮团可以有效的调节水质,降低水体中的氨氮、亚硝酸盐氮水平;各组的生物絮团体积指数(FVI)随养殖时间逐步增加,在第14天趋于稳定;随着C/N增高,尽管实验组水体中形成的生物絮团粗蛋白含量显著高于对照组(P<0.05),但是草鱼生长却呈下降趋势。综合而言,生物絮团技术应用于草鱼养殖适宜的C/N为15,该比值能促进生物絮团的形成,并能有效降低水中的氨氮、亚硝酸盐氮水平。     

混养锦鲤对微咸水凡纳滨对虾池水质及产量的影响

在6口面积均为0.4 hm2的微咸水池中养殖凡纳滨对虾,密度为7.5×105尾/hm2,其中4口混养锦鲤,密度分别为1500、3000、60001、2 000尾/hm2,研究混养锦鲤对凡纳滨对虾池水质及产量影响。结果表明:混养池水质比较稳定,透明度、NH4+-N和NO2--N波动幅度较小且数值较低,混养池对虾平均产量为3345 kg/hm2,比单养池平均产量2268 kg/hm2高47.5%,其中混养锦鲤3000尾/hm2的池虾产量最高,达到3765 kg/hm2。     

鲢鱼糜与淀粉复合系统的微波糊化特性

在2 450 MHz频率的微波处理条件下,为了考察添加鲢鱼糜对小麦粉面团糊化的影响,将小麦粉、鲢鱼糜、NaCl和去离子水按比例混合制成鲢鱼糜面团,面团中鲢鱼糜含量分别为0%,10%,20%和30%(w/w,质量百分比),对样品面团中淀粉的介电特性和糊化特性进行研究。结果表明,对于相同尺寸的面团样品,添加鲢鱼糜可改善面团样品在电磁场中的加热均匀性。随着温度的升高,面团的介电常数和介电损失率分别在20~23和9~12内波动并呈下降趋势,微波的穿透深度因淀粉的糊化略有上升。淀粉的糊化速率随温度的升高而下降。降低样品中淀粉的含量,会使面团糊化活化能由113.54 kJ/mol下降至59.96 kJ/mol。     

Combined effects of fertilization rate, manuring and feed pellet application on fish performance and water quality in polyculture ponds

This study analyses the combined effects of organic and inorganic fertilization and of feeding with pellets on fish performance and water quality in a polyculture of common carp. Cyprinus Carpio L., silver carp. Hypophthalmichthys molitrix (Val.), grass carp. Ctenopharyngodon idella (Val.) and hybrid tilapia, Oreochromis niloticus L. x O. aureus Stetndachner. Experiments included six treatments, which are combinations of inorganic fertilisation (daily or fortnightly), manuring (supplied or not), feed pellets (supplied or not) and density of phytoplanktivorous fish species (high-density treatments with 50% more hybrid tilapia and 300% more silver carp than low-density treatments). The effects of the management procedures on fish weight, growth, survival and yield. plankton abundance, water quality, and their complex interactions at the different levels of the natural food web were analysed. The hypothesis that daily fertilization should increase algal production, which in turn should sustain a higher density of phytoplanktivorous fish, proved to be correct within certain limits. Algal reproduction rate was higher under daily fertilization, pointing to better supply of food for herbivorous fish, while algal biomass was similar under both fertilization regimes, pointing to the utilization of that algal food supply. The increased algal food supply sustained a 50% density increase of the omnivorous tilapia, but not the 300% density increase of the grazer silver carp.     

Effects of increasing the stocking density of large carps by 20% on 'cash' carp–small fish polyculture of Bangladesh

This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for the farmers' family consumption and of large carp species as a cash crop. The objectives of this experiment were to assess the effects on fish performance and on the environment of adding 20% large fish to the basic ‘cash crop’ carp–small fish polyculture consisting of 10 000 fish ha^?1 of the large carp rohu Labeo rohita (Hamilton), catla Catla catla (Hamilton) and common carp Cyprinus carpio (L.) at a species ratio 1:1:1, and 15 000 fish ha^?1 of each small indigenous fish punti Puntius sophore (Hamilton) and mola Amblypharyngodon mola (Hamilton) (control). The treatment ponds were stocked with additional 2000 large fish ha^?1, either all rohu, or all catla, or all common carp, or half rohu and half common carp, or half catla and half common carp. The results obtained and the analysis of interactions through the food web that affect food resource availability of the different fish species and account for the trends and differences observed among treatments confirm the positive effect of common carp on rohu reported in previous experiments and show that a 20% increase in large carps stocking neither affect the survival of the large carps nor reduce harvesting biomass of the small fish for the farmer's family consumption. Increased stocking densities of each large carp species did not significantly reduce its own harvesting weight and mean growth rate, while significantly increased rohu and catla (but not common carp) harvesting biomass and yield. The complex relations between species led to inter‐ and intraspecific competition, which in some treatments increased growth or yield of one species and in other treatments of other species, so that the gains on one species and the losses on the other led to no significant total harvested biomass differences between treatments. Yet, the results herein reported may help farmers to select their species stocking ratios. Thus, if the main target of the farmer is rohu, then a stocking density increase of 10% common carp and 10% rohu would improve rohu growth rate (due to common carp) and result in 50% higher rohu harvesting biomass and yield. If the main target of the farmer is catla, then a 20% increase in catla stocking density would lead to 20% higher catla harvesting biomass.     

Effects of organic carbon addition on water quality and growth performance of bottom- and filter-feeding carp in a minimum-water-exchange pond polyculture system

A 120-day evaluation was performed to determine the impacts of various carbon source supplements on the water grade and production of bottom- and filter-feeding carp inside a minimum-water-exchange system. The outcomes revealed that the overall ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total inorganic nitrogen, and orthophosphate concentrations in every one of the carbon source treatments were significantly less (P?<?0.05) than the control. The net production of silver carp and bighead carp in the molasses treatment was significantly higher (P?<?0.05) than that in the control. The total feed conversion rates of the fish in the molasses and the mixed carbon source treatments were significantly lower (P?<?0.05) than in the control, while the total protein efficiency ratio values in the corn starch, molasses, and mixed carbon source treatments were significantly higher (P?<?0.05) than those in the control. The bioflocs significantly (P?<?0.05) impacted the muscle makeup of crude protein, crude fat, and ash of mirror carp. The current examination showed that the increased generation and feed used in mirror, silver, and bighead carp may be reached with an enhanced water grade when different carbon sources were added, while the use of molasses, an organic carbon source, was optimal compared to the other carbon sources due to its low price and good effect.     

甲壳素发酵液养殖草鱼、鲢鱼幼鱼试验

为研究甲壳素发酵液对草鱼和鲢鱼幼鱼养殖效果,用商品壳聚糖作参比,基础饲料为对照组,分析甲壳素发酵液对鱼体生长和水质环境等影响。试验结果表明,甲壳素发酵液处理组草鱼和鲢鱼幼鱼质量相对增长率比对照组高36.25%和122.47%(P0.05),草鱼体内脂肪酶、蛋白酶和淀粉酶3种消化酶分别比对照组高144.39%、29.53%和29.75%,鲢鱼体内消化酶比对照组高48.06%以上(P0.05)。与对照组比较,甲壳素发酵液显著降低水中亚硝态氮(61.84%)、氨态氮(30.06%)、总磷含量(52.43%),提高了草鱼对嗜水气单胞菌抗性。在试验条件下,甲壳素发酵液对草鱼和鲢鱼幼鱼起到一定的促生长作用,并能改善水质环境,甲壳素发酵液具有作为微生态制剂开发应用的潜力。     

The effect of C/N ratio on bacterial community and water quality in a mussel‐fish integrated system

A 30‐day experiment was conducted to evaluate the effect of C/N ratio on water quality and bacterial community in an integrated system comprising one molluscan species (pearl mussel Hyriopsis cumingii) and two fish species (gibel carp Carassius gibelio and silver carp Hypophthalmichthys molitrix) at five C/N ratios (6, 8, 10, 12 and 14). The mussel and fishes were reared in the experimental tanks (400 L), but gibel carp received formulated feed. Water quality in the experimental tanks was analysed on day 0, 10, 20 and 30, and bacterial community in the water column and sediment was analysed on day 30. Total nitrogen, total phosphorus and total organic carbon accumulated in the tanks over time. Ammonia and nitrite decreased with the increase in C/N ratio. Bacterial community in the water column and sediment changed at the phylum and genus levels with the increase in C/N ratio, and the critical C/N ratio causing a functional shift of bacterial community occurred at 10 in water column and 12 in sediment. The increase in C/N ratio benefited the growth of both potential probiotics and pathogenic bacteria. The high C/N ratio enhanced the bacterial functions of chemoheterotrophy and hydrocarbon degradation, but depressed the functions of nitrification and denitrification in the water column and sediment respectively. This study reveals that the C/N ratio can be used as a tool to manipulate the bacterial community and water quality in the mussel‐fish integrated system.