首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   126篇
  国内免费   3篇
  完全免费   83篇
  水产渔业   212篇
  2020年   24篇
  2018年   15篇
  2017年   16篇
  2016年   21篇
  2015年   20篇
  2014年   16篇
  2013年   12篇
  2012年   22篇
  2011年   15篇
  2010年   7篇
  2009年   11篇
  2008年   13篇
  2007年   6篇
  2006年   5篇
  2005年   4篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  1999年   1篇
  1997年   1篇
排序方式: 共有212条查询结果,搜索用时 31 毫秒
1.
凡纳滨对虾低盐度养殖池浮游藻类群落研究   总被引:14,自引:0,他引:14  
在44口凡纳滨对虾低盐度养殖池中共鉴定藻类7门62属113种,蓝藻26种,绿藻54种,硅藻14种,裸藻11种,隐藻3种,甲藻4种,金藻1种。绿藻门种类最多,占藻类种类数的47·8%,其次为蓝藻门占23·0%,硅藻占12·4%,裸藻占9·7%。优势种主要为蓝藻,典型优势种有螺旋藻(Spirulinasp.),假鱼腥藻(Pseudoanabaenasp.),弯形尖头藻(Raphidiopsis curvata),针状蓝纤维藻(Dactylococcopsis acicularis)等,其中螺旋藻的优势度平均达到50%,为主要优势种。常见的绿藻有栅藻(Scenedesmusp.),衣藻(Chlamydomonassp.),小球藻(Chlorella vulgaris)等;常见的硅藻为梅尼小环藻(Cyclotella meneghinian),卵形隐藻(Cryptomonas ovata)、啮蚀隐藻(C.erosa)和绿裸藻(Euglenavirdis)在虾池中比较常见。养殖池中浮游藻类的种类数平均为43±9种,多样性指数平均为2·19±0·56,个体数量平均为1·45±0·87×108个/L;藻类的种类、数量及生物量表现为养殖前期低后期高的特征,而多样性表现相反,藻类的组成直接影响对虾的生长。  相似文献
2.
祟明东滩团结沙鱼类群落多样性与生长特性   总被引:10,自引:1,他引:9  
研究了长江口祟明东滩团结沙5~8月间的鱼类多样性和生长特性。初步调查表明,祟明东滩团结沙共有鱼类9目19种,以鲤形目最多,鲻形目次之。这些鱼类分为4个主要生态类型,包括河口性鱼类4种、近海鱼类3种、江海洄游型鱼类4种和淡水鱼类8种。鱼类群落多样性较低,以个体数为单位计算的Shannon-Wiener多样性指数H′为2.790,Simpson优势度指数λ为0.198,Pielou种类均匀度指数J′为0.657。主要优势鱼类为窄体舌鳎、刀鲚、长蛇鮈、鲻、鲫、中国花鲈和中华鲟等7种,个体都较小。这7种鱼中窄体舌鳎、刀鲚、长蛇鮈、鲻、鲫和中华鲟呈等速生长,而中国花鲈为异速生长,肥满度最大的是鲫,最小的是刀鲚。5~8月间每个月渔获物的种类与数量组成有一定差异。为了更好地保护长江口祟明东滩的鱼类资源,应加强长江口渔业生态环境的综合治理,加大增殖和保护鱼类资源的力度,充分发挥长江口中华鲟自然保护区的保护功能。  相似文献
3.
淀山湖轮虫多样性及生物量时空变化   总被引:8,自引:0,他引:8       下载免费PDF全文
2004年1月至2006年12月逐月对淀山湖轮虫种类组成、生物量和生物密度的时空变化规律及其生物多样性进行了调查研究,并分析了轮虫密度和水温、叶绿素a的关系。经鉴定,共发现轮虫53种(属),优势轮虫包括针簇多肢轮虫Polyarthra trigla、角突臂尾轮虫Brachionus angularis、萼花臂尾轮虫Brachionus calyciflorus、螺形龟甲轮虫Keratella cochlearis、曲腿龟甲轮虫Keratella valga、晶囊轮虫属Asplanchna spp.、长三肢轮虫Filinia longiseta、椎尾水轮虫Epiphanes senta等,优势种的密度之和分别占当年度轮虫总密度的87.2、82.8和82.8%。3年轮虫平均密度和生物量分别为2514ind/L和2.94mg/L,2005年3月份St6轮虫密度高达11700ind/L。轮虫密度(ind./L)和生物量(mg/L)季节分布一致,均为春季(4862和5.45)>秋季(2300和3.45)>夏季(1773和1.88)>冬季(940和0.45);在水平分布上,表现为湖心高、进水口和出水口较低、处于网围养殖附近的St3轮虫密度最低的变化趋势。各站点3年平均H为2.27(变幅为2.08-2.50),Marglef指数D平均为2.3(变幅1.1-3.8)。淀山湖轮虫密度和水体中的叶绿素a含量呈极显著相关,回归方程为:轮虫密度(ind./L)=521.6+64.11Chl.a (µg/L)(r=0.634, P<0.001)。  相似文献
4.
镜泊湖大型底栖动物群落调查   总被引:6,自引:0,他引:6       下载免费PDF全文
2006年春、夏、秋3个季节对镜泊湖大型底栖动物群落特征和生物多样性进行了调查研究.结果表明,镜泊湖大型底栖动物主要隶属于3门、9科、26种.其中水栖寡毛类2科、8属、11种,为绝对优势类群,其密度呈现季节性差异,在春季最高(951.45个/m2),夏季最低(706.40个/m2);其次,优势类群为水生昆虫,夏季密度最高(840.26个/m2),秋季最低(319.47个/m2).霍甫水丝蚓(Limnodrilus hoffmeisteri)和前突摇蚊(Proeladius sp.)幼虫等耐污种为底栖动物的优势种,同时也是镜泊湖水体污染的指示生物.底栖动物群落的Shannon-Wiener指数(H')和Pielou均匀度指数(J)都表现为春季最大,夏季次之,秋季最小;Margalef物种丰富度指数(d)在各季节差异不大;Simpson优势度指数(D)和BI指数都表现为秋季最大,夏季次之,春季最小.采用Shannon-Wiener指数和BI指数对该水体污染状况进行了评价,该湖区水质污染程度为轻度一中度污染状态.  相似文献
5.
九孔鲍育苗池附着基上底栖微藻群落及其多样性   总被引:5,自引:0,他引:5       下载免费PDF全文
2006年9月14至10月26日对福建省漳浦县下蔡九孔鲍(Haliotis diversicolor supertexta)育苗池进行定点采样。检测结果共鉴定底栖微藻24属62种,其中硅藻21属59种,绿藻、蓝藻和褐藻各1种。附着基上底栖微藻的优势种有12种,全部为硅藻,如盾卵形藻微小变种(Cocconeis scutellum var.parva)、小形舟形藻(Navicula parva)、咖啡双眉藻(Amphora coffeaeformis)、琴式菱形藻(Nitzschia panduriformis)等。优势种的优势度突出。常见种有25种,少见种有27种。优势种和常见种多是能够适应底栖环境的种类。附着基上底栖微藻种类及多样性指数育苗早期波动大,后期逐渐稳定,底栖微藻多样性指数平均为0.980~1.959,结果表明,底栖微藻群落结构的演变与鲍幼体摄食活动有很大的相关性。  相似文献
6.
通过对1982、1993、2003和2008年渤海莱州湾海域位置相同的12个站位的鱼卵、仔稚鱼调查资料分析,研究了该海域鱼卵、仔稚鱼的种类组成及生物多样性的年代际变化。结果表明,莱州湾鱼卵、仔稚鱼种类大幅减少,由1982年的27种减少到2003年的12种和2008年的14种。鱼卵、仔稚鱼个体资源数量下降趋势明显,2008年个体数量分别为1982、1993和2003年的31.58%、0.61%和5.77%。种类组成相似性分析表明,莱州湾鱼卵、仔稚鱼种类组成年代际间存在显著差异(P<0.05),且有变动加快的趋势。生物多样性指数1993年最低,之后呈上升趋势。  相似文献
7.
Asia dominates global aquaculture production accounting for over 80% of the total and the mainstay in Asian aquaculture is finfish. Over the years, Asia has experienced a number of inter‐continental and intra‐continental transfers/introductions/translocation of finfish species, between nations and watersheds, beyond their natural range of distribution, primarily for aquaculture development. In this article all such species are referred to as alien species. An attempt is made to evaluate the importance of the production of alien species in selected Asian nations, using statistics of the Food and Agriculture Organization. Also, negative effects, if any, based on literature surveys, of alien species in relation to displacement of indigenous species, and on biodiversity and/or genetic diversity together with associated pathogen transfers are evaluated. The major alien species, based on their significance to Asian inland aquaculture considered, are the tilapias, catfish, Chinese and Indian major carps and common carp. It is estimated that currently alien species account for nearly 12% of the cultured finfish production (2.6 million tonnes) in Asia, valued at US$ 2.59 billion, and the contribution exceeds 40% when Asian countries excluding China are taken into consideration. Inland finfish aquaculture in some Asian nations, such as Indonesia and the Philippines, is predominated by alien species, and in some others, e.g. Bangladesh and India, the contribution from alien species has been increasing steadily. It is suggested that overall alien finfish species have done little ecological harm to native flora and fauna. However, in the wake of increasing anthropogenic development taking place in watersheds the resulting environments are often made unconducive to indigenous species but not to some alien species, thereby potentially and indirectly making the latter invasive.  相似文献
8.
Introduction of non‐native freshwater fish: is it all bad?   总被引:3,自引:3,他引:0  
Risk perceptions are important to the policy process, but there is often a well‐established pattern of small risks being over assessed. This is also true with the issue of non‐native freshwater fish introductions, where a great majority of research focuses on the few negative cases. The attitude towards ‘non‐natives’ is a continually evolving process and varies according to current societal values. Here I show that on the global scale, the majority of freshwater fish introductions are not identified as having an ecological impact while having great societal benefits. Case studies from the African lakes are discussed in order to illustrate contrasting outcomes following fish introductions. Looking into the future, the environmental changes that freshwater ecosystems may encounter will have inevitable implications on the distribution of our native freshwater fish species and the need to rely on non‐native introductions may become a growing reality. Aquaculture production is regularly increasing and our dependence on it is likely to become greater as it provides an important substitute for the declining production of capture fisheries. With it the number of freshwater fish introductions will increase and a more realistic attitude, albeit controversial, will need to be debated. This would mean protecting some introductions that present beneficial outcomes for biodiversity alongside a more systematic ban of species or families of fish presenting a higher historical ecological risk. The public perception of risk is something which cannot be ignored by any government or ruling body, but in order to gain public support in the fight for conservation of freshwater fish biodiversity, the message needs to be clear, detailed and educational.  相似文献
9.
Fishes that feed from live corals (corallivores) are a conspicuous component of healthy coral reef environments. However, knowledge of the occurrence and ecological significance of this feeding mode is fragmentary. Historically, very few fish were considered capable of feeding from live coral, and those few that did were considered ecologically insignificant. More recently, the role of corallivores has been re-evaluated; published records document 128 corallivorous fish species from 11 different families, with 69 of these belonging to the family Chaetodontidae. Other families, including the Labridae, Tetraodontidae, Balistidae, Monacanthidae, Pomacentridae and Scaridae, all have between seven and ten coral-feeding species. One-third of coral-feeding fishes feed almost exclusively on corals, with more than 80% of their diet based on coral. Corallivorous fish show distinct prey preferences and consume only a small subset of available corals, usually the genera Acropora , Pocillopora and Porites . This selective predation by corallivores can limit abundance and distribution of preferred corals. Chronic predation by corallivores may also exacerbate effects of coral disturbance (e.g. climate-induced coral bleaching), impeding reef recovery and causing further coral loss. Conversely, the cover of preferred corals can be a primary determinant of corallivore abundance and physiological condition. Owing to this close association, obligate corallivores invariably decline in response to loss of coral cover. Increased knowledge of the number of corallivores and their diets suggest that this feeding mode is more important to coral reef food webs than traditionally thought.  相似文献
10.
长江干流安庆段浮游植物群落结构特征   总被引:2,自引:0,他引:2  
为了解长江干流安庆段浮游植物群落结构特征,分别于2015年4月(春季)、7月(夏季)和9月(秋季)对长江干流安庆段浮游植物进行了调查.结果显示:本次调查共检出浮游植物5门22科33属54种(含变种).以硅藻门种类最多,占总种数的46.30%;其次是蓝藻门和绿藻门,分别占24.07%和22.22%;黄藻门和甲藻门的种类相对较少,占5.56%和1.85%.优势种为蓝藻门的小颤藻(Oscillatoria tenuis)、极大螺旋藻(Spirulina maxima)、湖沼色球藻(Chroococcus minutus),绿藻门的小球藻(Chlorella vulgaris)、集星藻(Actinastrum hantzschii)以及硅藻门的尖针杆藻(Synedra acus).浮游植物密度为1.228×104~33.002×104 ind./L,均值为9.453×104 ind./L;生物量为0.005~0.512 mg/L,均值为0.157 mg/L.密度和生物量最高值均出现在皖河口采样断面(7月)、最低值均出现在杨家套采样断面(4月).研究结果表明:浮游植物密度和生物量在空间分布上差异均不显著,季节变化上则均表现出显著性差异.利用Shannon-Wiener指数和Pielou 均匀度指数分析浮游植物群落结构特征,Shannon-Wiener指数变化范围为0.918~3.147,均值为2.539;Pielou 均匀度指数变化范围为0.796~1.000,均值为0.893.Shannon-Wiener指数在空间分布和季节间均无显著性差异;Pielou 均匀度指数在空间分布上无显著性差异,但在季节间变化上则表现出显著性差异.浮游植物多样性指数结果表明长江干流安庆段水质状况介于清洁型/β-中污型.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号