A preliminary investigation of the fish food web in the Gironde estuary,France, using dietary and stable isotope analyses     

S. Pasquaud  P. Elie  C. Jeantet  I. Billy  P. Martinez  M. Girardin 《Estuarine, Coastal and Shelf Science》2008

Carbon and Nitrogen stable isotopes and stomach contents analyses were used to investigate an estuarine fish food web and identify the contribution of these two methods to the knowledge and understanding of the food web's structure and its functioning. The nine most abundant fish species during the warm period in the Gironde estuary (southwest France, Europe) are examined. Observation of the stomach contents reflects a variety of feeding modes between fish species that consume a diverse assortment of prey, with limited dietary overlap. Nevertheless, when regarding the whole fish community, few prey species dominate the stomach contents. Nitrogen isotope ratios indicate a high intraspecific variability inducing an interspecific covering of the signatures. However, a tendency to δ¹⁵N enrichment according to the trophic position of the species studied was observed. Fish assemblages show a trend towards enrichment of their carbon isotopic signatures from the upper estuary (−20.8 ± 1.8‰) towards the lower estuary (−18.3 ± 1.6‰). But whatever the capture zone considered, most of the individual δ¹³C values for each fish analysed are comprised between −22 and −16‰. Only few specimens, belonging to migratory amphihaline species, have significantly lighter values.  相似文献   

地图集:重构复杂非线性地理世界的“百科全书”     

王家耀 《测绘地理信息》2021,46(1):1-8

地图学是一门经过数千年的演进发展形成的科学,地图(地图集)是地图科学研究的主阵地,是任何时代和社会都不可或缺的,对人们的工作、学习和生活具有重要作用和意义。首先,简要论述了地图学作为一门科学的社会实践和科学实践的演进发展规律,以及地图集的特点;然后,从哲学角度分析与论述了地图是怎样重构复杂非线性地理世界的(实现由"地理世界"到"地图世界"的转变),人们是怎样利用地图进一步认识复杂非线性地理世界的(实现由"地图世界"到"地理世界"的转变),提出了基于传感器网络的由"感知的地理世界"到"重构的地理世界"再到"认知的地理世界"、指导行动并反馈信息的"双向"转变的认知模式;最后,论述了地图集作为重构复杂非线性地理世界的"百科全书"的作用,举例说明了中国改革开放以来地图集的快速发展和水平的大幅提升,并阐明人工智能时代中国地图集成果将比以往任何时候都更加兴旺发达,地图集作为人们进一步认知复杂非线性地理世界的"百科全书"的功能作用将比以往任何时候都更加强大。  相似文献   

基于GDS室温条件下盐渍土强度特性的试验研究     

张洪萍  杨晓华  韩云山 《中国地质灾害与防治学报》2011,22(1):133-138

以新疆(北疆)地区S201公路沿线的盐渍土为研究对象,通过三轴剪切试验对盐渍土的强度特性进行了较系统的研究。试验结果表明,盐渍土与非盐渍土在力学性能上没有本质的区别,即应力-应变曲线大致都呈双曲线型,抗剪强度与破坏面上的法向应力成正比,且符合库伦定律;含水量和含盐量的变化导致试样发生的破坏形式不同。在含水量低和含盐量高时,试件具有脆性破坏的特征,在含水量高和含盐量低时逐渐显示出塑性特征;含水量和含盐量的变化对盐渍土的强度参数有重要影响,其中对粘聚力C的影响较大,表现较明显,而内摩擦角仅对含水量的变化表现敏感;极限强度与含水量和含盐量之间的关系符合二次抛物线变化规律,在不同应力作用下,抛物线形式不同。  相似文献   

顾及性别差异的电子地图空间认知分析     

颜言  龙毅  沈倩茹  王剑 《地理与地理信息科学》2011,27(4):48-51

电子地图是人们进行地理空间信息应用与认知的重要载体,而性别差异影响着地图空间认知的结果。该文通过一系列地图认知实验,分析了不同性别在观察地图、认知地图、形成心象地图和表述地图信息过程中的差异。实验表明,男性对空间关系较为敏感,而女性对要素注记、形状、位置及空间面积的认知能力更为突出。  相似文献   

FOOD HABITS AND SEASONAL VARIATION OF STOMACH CONTENTS OF TONGUE SOLE CYNOGLOSSUS SEMILAEVIS (GUNTHER) IN THE BOHAI SEA     

窦硕增 《中国海洋湖沼学报》1993,(1)

Examination of the food habits and seasonal variation of the stomach contents of adult tongue sole, Cynoglossus semilaevisGunther) taken in July 1982-July 1983 from Laizhou Bay and the Huanghe River estuary of the Bohai Sea showed Crustacea, bivalvia and small fishes comprised the main prey. Invertebrates such as polychaeta, cephalopoda, gastropoda, echinodermata and actiniaria were also intermittently found in them. They intensively fed all the year round (monthly feeding rate of over 80%). The main food items were Alpheus japonica, Alpheus distinguendus, Oratosquilla oratorio, Eucrate crenata and Carcinoplax vestitus, etc. In summer and autumn, the portion of bivalvia such as Cultellus attenuatus and Musculus senhousei increased steadily. From summer to winter, a stable proportion of small fishes such as Rhinogobius pflaumi and Setipinna taty was in the diet.  相似文献   

二维和三维电子地图的空间认知差异研究     

柳佳佳  葛文  薛宁 《海洋测绘》2014,(2):76-79

讨论了二维和三维电子地图在空间认知特点、空间认知模式和空间认知效果方面的差异。与纸质地图相比,二维电子的地图的空间认知具有动态性、交互性以及制图和读图过程的模糊化等特点,三维电子地图的认知效率更高、认知维度和深度更广。空间认知模式方面,二维电子地图类似于"阅读式",而三维电子地图则类似于"观看式"。二维电子地图对位置、距离、方向等空间格局的认知效果较好,而三维电子地图对目标、形状等空间对象的认知效果较好。  相似文献   

汶川地震对北京公众灾害认知的影响     

苏筠  谢静晗  马飞燕  高爱玲 《地震研究》2011,34(3):378-383

通过对北京702名公众进行问卷调查,了解其在汶川地震前后灾害认知的变化及对风险沟通的看法,经过赋分计算及相关分析,结果显示:被调查公众对汶川灾害高度关注,电视、网络是公众获取信息最主要的渠道;被调查者所掌握的灾害应急避险知识水平低,而且在地震后这一情况没有得到改善,但是减灾意识及行为倾向有所改善.样本个体的教育水平、性...  相似文献   

DNA-based identification methods of prey fish from stomach contents of 12 species of eastern North Pacific groundfish     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Stomach content analysis of eastern North Pacific groundfish has been conducted routinely by researchers interested in understanding trophic interactions between key predator species and their prey. Identification of prey by traditional morphological methods has limitations however, due to the loss of identifiable characters from digestion and morphological similarities between taxa. Furthermore, some forage fish (e.g., osmerids, ammodytids, and juvenile gadids), common prey of Bering Sea and Gulf of Alaska groundfish, are difficult to distinguish because of their slender or fusiform shape, disarticulating easily during digestion. DNA-based identification methods were developed to differentiate among 18 fish species, some that are found at depths greater than 200 m, from four taxonomic families: Ammodytidae and Osmeridae (forage fish), Pleuronectidae (flatfish), and Gadidae (gadid fish). Polymerase chain reaction (PCR) amplification of a 739 basepair section of mitochondrial DNA cytochrome c oxidase I and an 862 basepair section of mitochondrial DNA cytochrome b was followed by restriction digest assays and resulted in species level resolution for 16 of 18 species of interest. PCR restriction digest assays applied to fish prey from stomach contents of groundfish indicated the presence of several target species, eulachon (Thaleichthys pacificus), walleye pollock (Gadus chalcogrammus), searcher (Bathymaster signatus), rock sole (Lepidopsetta bilineata), yellowfin sole (Limanda aspera) and either Bering flounder (Hippoglossoides robustus) or flathead sole (H. elassodon). The PCR restriction digest protocols improved the identification rate of predated fish from stomach contents compared to identification by conventional taxonomic methods alone, and DNA sequence analysis further resolved identification of unknown prey fish samples.  相似文献   

土地调查项目监理内容与方法研究     

李淑贞 《现代测绘》2014,(1):52-54

近几年监理制度引入测绘工程,本文以监理制度在土地调查项目中的应用为例,通过分析土地调查项目监理的流程,研究土地调查项目监理的内容和方法,对土地调查项目监理细则的编写起到一定借鉴作用。  相似文献   

地图上居民地空间信息的特征度量法   总被引：1，自引：1，他引：0  

刘慧敏  邓敏  樊子德  卢启栋 《测绘学报》2014,43(10):1092-1098

地图的基本功能之一是载负和传输空间信息。地图空间信息量是衡量地图上空间要素及其关系与要素空间分布状况复杂程度的定量描述指标,可为制图综合和质量评价提供依据。本文以地图上居民地空间信息度量为研究对象,从地图空间信息的本质特征出发,结合空间信息认知的层次性特点,将居民地空间特征划分为三个层次,并相应地将其空间信息构成划分为：元素层次居民地面要素的几何形态信息、邻域层次相邻居民地的空间关系信息、整体层次居民地的聚群结构信息。进而,分别建立三个层次空间特征的定量描述指标,在此基础上建立基于空间特征的几何形态信息、分布关系信息和聚群结构信息度量方法。最后,通过试验分析验证了所提方法的合理性和优越性。  相似文献