淡化速度和幅度对凡纳对虾幼体存活和活力的影响   总被引：1，自引：0，他引：1  

廖永岩  钟导宏 《海洋通报》2004,23(1):58-63

进行了淡化速度、幅度对凡纳对虾(Litopenaeus vannamei)的影响试验，结果表明：每36h和24h降低盐度2～3的两种淡化速度，对虾苗存活率较高，分别为86．7％和83．3％；淡化时间分别为396h和264h。每12h降低盐度2～3的淡化速度，从盐度29．7降至16．3，存活率为90．0％；从盐度16．3降至0，成活率为60.3％。每次降幅为1．3～1．4和2．6～2．7时，最终存活率较高，最终淡化到纯淡水中的存活率分别为83.3％和80．0％。每次降幅度为5.3～5．4时，在降到19．0以前，存活率都还较高，但此后的效果不佳，淡化至淡水时，成活率仅为53.3％。  相似文献   

不同饲料对凡纳对虾幼体生长与发育的影响   总被引：3，自引：0，他引：3  

罗杰  刘楚吾  杜涛  刘丽 《海洋科学》2004,28(1):11-14

采用不同的饲料系列饲养各阶段凡纳对虾(Lito-penaeus vannamei)的幼体和仔虾，实验结果表明：在潘状幼体期(Z)～糠虾幼体Ⅱ期(M2)，投喂骨条藻 人工配合饲料系列，比单纯投喂骨条藻或单纯投喂人工配合饲料的成活率分别高18．5％和26.7％；糠虾Ⅱ期(M2)以后单独投喂人工配合饲料或单独投喂卤虫无节幼体的成活率无明显的差别；在人工育苗后期，用人工配合饲料代替卤虫无节幼体，育苗的成活率并没有下降。  相似文献   

The life cycle of contributors in collaborative online communities -the case of OpenStreetMap     

Daniel Bégin  Rodolphe Devillers  Stéphane Roche 《International journal of geographical information science》2018,32(8):1611-1630

Over the last two decades, online communities have become ubiquitous, with millions of people accessing collaborative project websites every day. Among them, the OpenStreetMap project (OSM) has been very successful in collecting/offering volunteered geographic information (VGI). Very different behaviours are observed among OSM participants, which translate into large differences of lifespan, contribution levels (e.g. Nielsen’s 90–9-1 rule) and attitudes towards innovations (e.g. Diffusion of innovation theory or DoIT). So far, the literature has defined phases in the life cycle of contributors only based on the nature of their contributions (e.g. role of participants and edits characteristics). Our study identifies the different phases of their life cycle from a temporal perspective and assesses how these phases relate to the volume and the frequency of the contributions from participants. Survival analyses were performed using both a complementary cumulative distribution function and a Kaplan-Meier estimator to plot survival and hazard curves. The analyses were broken down according to Nielsen and DoIT contributors’ categories to highlight potential explanatory variables. This paper shows that two contribution processes combine with three major participation stages to form six phases in contributors’ life cycle. The volume of edits provided on each active day is driven by the two contribution processes, illustrating the evolution of contributors’ motivation over time. Since contributors’ lifespan is a universal metric, our results may also apply to other collaborative online communities.  相似文献   

Cu2+、Zn2+、SDS、DBS对脊尾白虾的毒性试验   总被引：4，自引：0，他引：4  

郑琰晶  魏社林  吴进孝  罗步仪  黄韧 《热带海洋学报》2006,25(5):87-90

选用铜、锌2种常见重金属和十二烷基硫酸钠(SDS)、十二烷基苯磺酸钠(DBS)2种阴离子表面活性剂对脊尾白虾Palaemon carincauda仔虾进行96h急性毒性试验。结果表明,Cu2 、Zn2 、SDS、DBS对脊尾白虾仔虾的96h LC50分别为0.34、0.82、14.3和14.4 mg.L-1。将脊尾白虾仔虾对这4种毒物的敏感性与文献报道的其它动物进行了比较,结果认为可以将其作为毒性测试的标准试验生物。  相似文献   

海水温度和盐度对泥蚶幼虫和稚贝生长及存活的影响   总被引：24，自引：0，他引：24  

尤仲杰  徐善良  边平江  陈坚 《海洋学报》2001,23(6):108-113

1996～1997和1999年在浙江省乐清市东发水产育苗场和福建省宁德市四海水产育苗场分别研究了海水温度和盐度对泥蚶浮游幼虫和稚贝生长及存活的影响,结果表明,泥蚶浮游幼虫的适宜温度为25～33℃,最适生长温度为28～30℃.稚贝的适宜温度为15～35℃,最适生长温度为25～30℃.浮游幼虫的适宜盐度为16.54～30.02,最适生长盐度为1654～23.38;稚贝的适宜盐度为10.01～30.02,最适生长盐度为10.01～23.38.泥蚶幼虫和稚贝对高温和低盐海水有较强的适应能力,这与它们夏季的繁殖期和自然分布于内湾河口区是相适应的.  相似文献   

Comparisons of cultured triploid and diploid Atlantic salmon(Salmo salar L.)   总被引：1，自引：0，他引：1  

O'Flynn  F. M.; McGeachy  S. A.; Friars  G. W.; Benfey  T. J.; Bailey  J. K. 《ICES Journal of Marine Science》1997,54(6):1160-1165

  相似文献   

Migration and survival of farmed Atlantic salmon (Salmo salar L.) released from two Norwegian fish farms   总被引：1，自引：0，他引：1  

Hansen  Lars P. 《ICES Journal of Marine Science》2006,63(7):1211-1217

  相似文献   

海水盐度对牙鲆仔稚鱼的生长、存活率及白化率的影响   总被引：32，自引：0，他引：32  

王涵生 《海洋与湖沼》1997,28(4):399-405

１９９３年１１月２０日自鹿儿岛养殖业购得自然产卵获得的牙鲆受精卵，经空运、陆驼至福冈的九州大学附属水产试验所，仔鱼翌日孵出，３ｄ后开口。以此材料观察研究试验室条件下不同海水盐度对牙鲆仔稚鱼的生长，存活率及白化率的影响。试验分４组，盐度分别为：１组（自然海水对照组），３０．５－３１．８；２组，２６．０：３组，２１．０；４组，１６．０。每组设２个重复，使用１００１透明玻璃钢水槽，每槽放２０００尾刚开口  相似文献   

Effect of temperature on embryonic and larval development of bream (Abramis brama L.)     

Dariusz Kucharczyk  Miroslaw Luczynski  Roman Kujawa  Piotr Czerkies 《Aquatic Sciences - Research Across Boundaries》1997,59(3):214-224

Influence of water temperature on embryonic and larval development of bream (Abramis brama L.) was stdied. Eggs of bream were incubated at eight constant water temperatures between 13.2 and 26.8°C. The temperature of 21.1°C gave highest hatching success, with no abnormalities in the eleutheroembryos and lowest mortality observed between eyed egg stage and the time of hatching. Developmental rate increased with increasing temperature. Duration of embryonic development (y; hours) decreased with increasing incubation temperature (x; °C) according to the formula: y=910.1−65.88 x+1.318 x². Larvae were reared at eight constant temperatures ranging from 13.5 to 34.0°C. The instantaneous growth rate in wet weight increased with increasing test temperature from 13.5 to 29.9°C, and then decreased at higher temperatures. Individual growth of fish and biomass production rate were highest at 27.9°C. This temperature is considered optimal when food availability and photoperiod are no limiting factors.  相似文献   

加入WTO后中国旅行社的生存与发展   总被引：1，自引：3，他引：1  

肖建成  余蓉 《云南地理环境研究》2003,15(3):13-22

中国入世后，旅游市场的进一步开放将有利于引进先进的经营管理经验，进一步发展中国得天独厚的旅游资源和劳动力优势。同时，伴随着服务贸易总协定(CATS)在各成员国的实施与经济全球化，中国旅行社的生存与发展将面临机遇和挑战。中国旅行社应勇敢面对挑战，从以下几个方面提高竞争力：(1)树立战略发展思想；(2)树立战略管理思想；(3)化危机为商机，积极成为网介者；(4)界定企业发展方向，发展产品核心功能；(5)迎合消费者需求与创新需求；(6)组建集团化旅行社；(7)实行跨国际化经营，参加国际竞争；(8)加强对外宣传。  相似文献