The Fish Assemblage of a Newfoundland Estuary: Diel, Monthly and Annual Variation     

D. A. Methven  R. L. Haedrich  G. A. Rose 《Estuarine, Coastal and Shelf Science》2001,52(6):669

Twice monthly sampling over two 16 month periods at a shallow site on Newfoundland's east coast showed the fish assemblage to be dominated by four taxa (Gasterosteus aculeatus, G. wheatlandi, Osmerus mordax, Gadus spp.) that accounted for 96% of the individuals collected. Of the 16 479 fish measured, 65% were adults based on the estimated size of first spawning. The fish assemblage was dominated (86%) by species with demersal eggs, several of which spawn at the same shallow sites used by juveniles as nursery sites. Coastal spawning and demersal eggs maintain offspring in coastal nursery areas where survival is thought to be increased. Number of species and number of fish were both correlated with water temperature being highest from mid-summer to early autumn and lowest in winter. Temperature, time of spawning, and movements of juveniles and adults facilitated grouping species into five assemblages based on seasonal abundance: seasonal periodic species (summer and winter), regular species, regular species collected in all seasons except winter, and occasional (rare) species. At the diel scale, two consistent species groupings were observed: species that showed no significant difference between day and night and species caught primarily at night. Number of night species exceeded day species by a factor of two. No seine-caught species in shallow water exhibited significantly higher catches during the day. Observations by SCUBA divers indicated some species were more abundant during day time at slightly deeper depths. This observation in conjunction with day and night seining in shallower water, suggests these species aggregate in deeper water during day and move to shallow waters at night.  相似文献   

Effect of placer mining on suspended sediment in reaches of sensitive fish habitat     

S. B. Pentz  R. A. Kostaschuk 《Environmental Geology》1999,37(1-2):78-89

 The McQuesten River system in central Yukon Territory, Canada, contains placer mines and reaches of sensitive fish habitat. Suspended sediment is supplied to the system by erosion of previously mined disturbed areas, bank erosion, resuspension of placer sediment deposited on bars, and active placer-mine discharges. Direct discharge from active placer mines did not have a large impact on suspended sediment in reaches of sensitive fish habitat in 1994–1995, although only two mines were active and concentrations did periodically exceed water quality objectives. Erosion of previously mined disturbed areas had a pronounced effect on suspended sediment during spring snowmelt and summer rainstorms in 1994–1995. Deposits in previously mined areas should be stabilized to reduce erosion and its downstream impact on fish habitat. Received: 10 November 1997 · Accepted: 30 March 1998  相似文献   

The interplay of sediment characteristics,depth, water temperature,and ocean currents shaping the biogeography of lancelets (Subphylum Cephalochordata) in the NW Pacific waters          下载免费PDF全文

Hsiu‐Chin Lin  Jen‐Ping Chen  Benny K K Chan  Kwang‐Tsao Shao 《Marine Ecology》2015,36(3):780-793

Lancelets (or amphioxus) are often found within the soft bottom of shallow tropical and temperate seas. The present study is the first to provide a fine‐scale biogeography of five species of lancelets (Asymmetron lucayanum, Branchiostoma belcheri, Branchiostoma japonicum, Epigonichthys cultellus, and Epigonichthys maldivensis) in the NW Pacific and examine the effects of multiple environmental parameters. From multivariate analyses, the distribution and abundance patterns of lancelets were explained by a combination of factors comprising depth, temperature of the collecting month, mean temperature of the coldest month in the year, medium particle size and silt/clay ratio of the sediments. In addition, ocean currents also affect their distribution range. The major occurrence of A. lucayanum and E. maldivensis was associated with the warm Kuroshio current, but E. maldivensis exhibited higher tolerance to low salinity and low temperature, and preferred substrata of slightly larger grain size, a lower ratio of suspended sediments, and deeper water. The closely related B. belcheri and B. japonicum exhibited fine‐scale habitat differentiation, and B. japonicum was abundant along the southern coast of China, where the salinity is lower in winter because of the China Coastal Current and the substratum is composed of very coarse sand with suspended sediments. Branchiostoma belcheri occurred in low abundance and was only recorded in Northern Taiwan and the Taiwan Banks. Epigonichthys cultellus was found only at the Taiwan Banks, which had deep water, coarse sand, and a negligible amount of suspended sediments.  相似文献   

Detecting subpixel deciduous components to complement traditional land cover classifications in Southwest Finland     

《International Journal of Applied Earth Observation and Geoinformation》2015

To ensure successful conservation of ecological and cultural landscape values, detailed and up-to-date spatial information of existing habitat patterns is essential. However, traditional satellite-based and raster classifications rely on pixels that are assigned to a single category and often generalized. For many fragmented key habitats, such a strategy is too coarse and complementary data is needed. In this paper, we aim at detecting pixel-wise fractional coverage of broadleaved woodland and grassland components in a hemiboreal landscape. This approach targets ecologically relevant deciduous fractions and complements traditional crisp land cover classifications. We modeled fractional components using a k-NN approach, which was based on multispectral satellite data, assisted by a digital elevation model and a contemporary map database. The modeled components were then analyzed based on landscape structure indicators, and evaluated in conjunction with CORINE classification. The results indicate that both broadleaved forest and grassland components are widely distributed in the study area, principally organized as transition zones and small patches. Landscape structure indicators show a substantial variation based on the fractional threshold, pinpointing their dependency on the classification scheme and grain. The modeled components, on the other hand, suggest high internal variation for most CORINE classes, indicating their heterogeneous appearance and showing that the presence of deciduous components in the landscape are not properly captured in a coarse land cover classification. To gain a realistic perception of the landscape, and use this information for the needs of spatial planning, both fractional results and existing land cover classifications are needed. This is because they mutually contribute to an improved understanding of habitat patterns and structures, and should be used to complement each other.  相似文献   

The influence of relative sediment supply on riverine habitat heterogeneity   总被引：1，自引：0，他引：1  

Sarah M. Yarnell  Jeffrey F. Mount  Eric W. Larsen 《Geomorphology》2006,80(3-4):310-324

The diversity of aquatic habitats in streams is linked to physical processes that act at various spatial and temporal scales. Two components of many that contribute to creating habitat heterogeneity in streams are the interaction between sediment supply and transport capacity and the presence of local in-stream structures, such as large woody debris and boulders. Data from previously published flume and field studies and a new field study on tributaries to the South Yuba River in Nevada County, California, USA, were used to evaluate the relationship between habitat heterogeneity, local in-stream structural features and relative sediment supply. Habitat heterogeneity was quantified using spatial heterogeneity measures from the field of landscape ecology. Relative sediment supply, as expressed by the sediment supply/transport capacity ratio, which controls channel morphology and substrate textures, two key physical habitat characteristics, was quantified using a dimensionless bedload transport ratio, q. Calculated q values were plotted against an ecologically meaningful heterogeneity index, Shannon's Diversity Index, measured for each study reach, as well as the percent area of in-stream structural elements. The results indicate two potential mechanisms for how relative sediment supply may drive geomorphic diversity in natural river systems at the reach scale. When less mobile structural elements form a small proportion of the reach landscape, the supply/capacity ratio dictates the range of sediment textures and geomorphic features observed within the reach. In these settings, channels with a moderate relative sediment supply exhibit the highest textural and geomorphic diversity. In contrast, when less mobile structural elements are abundant, forced local scour and deposition creates high habitat heterogeneity, even in the presence of high relative sediment supply.  相似文献   

环渤海海平面上升与三角洲湿地保护   总被引：26，自引：0，他引：26       下载免费PDF全文

肖笃宁  韩慕康  李晓文  刘岳峰 《第四纪研究》2003,23(3):237-246

环渤海地区三角洲是我国滨海重要的湿地发育区,在淤泥质滩地型湿地上发育着众多的动、植物群落,成为若干珍稀水禽的栖息地。从地面垂直形变与潮位资料等分析,黄河三角洲和辽河三角洲的地面下降速率为3～4mm/a和3.5～4.5mm/a,而相对海平面上升速率为45～5.5mm/a和5～6mm/a,预计至2050年总体的相对海平面上升量可达40～55cm。海平面上升对三角洲湿地的影响首先是直接淹没大片农田、油井和市区,其次是加剧海岸线的侵蚀与后退,还有风暴潮与洪涝灾害的加剧。针对三角洲湿地生态系统所面临的生态风险与人为活动干扰,有必要采取更加科学合理的保护与开发模式。本文介绍了生境更新与湿地调整的管理策略,以及淤长型滨海湿地的滚动开发模式。交替采用“渐进”与“跃进”的滚动开发,可保持湿地总量的动态平衡,有利于三角洲的可持续发展。  相似文献   

2004年内蒙古草原蝗虫大发生的气象生态条件分析   总被引：9，自引：1，他引：9  

刘玲  郭安红 《气象》2004,30(11):55-57

2004年，内蒙古草原蝗虫再度大面积爆发成灾，主要分布于锡林郭勒盟西部、乌兰察布盟北部、包头以北地区和巴彦淖尔盟北部地区。2004年冬春高温和5月上旬的降水对上述地区蝗虫虫卵的孵化出土比较有利，蝗虫虫蝻的始见期提前11天左右。干旱和荒漠化是自2000年以来内蒙古草原蝗虫连续爆发的主要气候因素。  相似文献   

Impact of habitat heterogeneity on plant community pattern in Gurbantunggut Desert     

QIAN Yibing  WU Zhaoning  ZHANG Liyun  SHI Qingdong  JIANG Jin  TANG Lisong 《地理学报》2004,14(4):447-455

This paper reports a geomorphologic landscape investigation, vegetation survey and soil sampling at 14 sites across the Gurbantunggut Desert between 87o37'09'-88o24'04'E and 44o14'04'-45o41'52'N. The study encountered 8 species of low trees and shrubs, 5 of perennial herbs, 8 of annual plants and 48 of ephemeral and ephemeroid plants. These species of plants represent one-third of the species found in the Gurbantunggut Desert, and their communities make up a large proportion of desert vegetation with great landscape significance. In the investigation we found that the plant communities are accordingly succeeded with the spatial variation of macro-ecoenvironment. Using Principal Component Analysis (PCA) and Correlation Analysis (CA) we found that the micro-ecoenvironment heterogeneity of aeolian sandy soil's physical and chemical properties such as soil nutrient, soil moisture, soil salt, pH etc. only impacted the diversity of herb synusia (PIEherb) of the desert, with a negative correlation. Meanwhile, the impact of microhabitat on the plant community pattern with an antagonistic interaction made vegetation's eco-distribution in a temporary equilibrium.  相似文献   

Application of lidar digital terrain modelling to predict intertidal habitat development at a managed retreat site: Abbotts Hall,Essex, UK     

Simon J. Blott  Kenneth Pye 《地球表面变化过程与地形》2004,29(7):893-905

A key question in designing any managed retreat site concerns the nature of the habitats which will be created, and their likely long‐term sustainability and development. Studies of historical sea wall failures in Essex have shown that former reclaimed areas may respond to renewed tidal ?ooding in different ways depending on a number of factors, most importantly the elevation of the land at the time of breach, which governs the frequency and duration of tidal ?ooding. This paper demonstrates how digital terrain modelling using airborne lidar data can be used to calculate the elevation of the land behind a breach and to predict the likely habitats which will be created. When combined with data from sites of historical sea wall failure, predictions can also be made about the likely geomorphological and biological evolution of the created habitats in the longer term. At Abbotts Hall on the northern side of Salcott Creek, Essex, where a managed retreat scheme was activated in October 2002, the highest areas above 2·35 m OD were predicted to develop stable saltmarsh, intermediate areas between 2·1 and 2·34 m OD to develop potentially unstable saltmarsh which is likely undergo internal dissection, and the lowest areas below 2·1 m OD to remain as mud?at or lagoon. Approximately 38 per cent of the site was predicted to develop stable saltmarsh, and nearly 50 per cent to remain as lagoon or mud?at. Monitoring is now being undertaken but it will be several years before the accuracy of the predictions can be assessed. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

河道内生态需水估算方法及其评述   总被引：38，自引：0，他引：38       下载免费PDF全文

钟华平  刘恒  耿雷华  徐春晓 《水科学进展》2006,17(3):430-434

针对目前常用的水文指标法、水力学法、整体分析法和栖息地法,4大类河道内生态需水估算方法就其适用条件和范围作了相关评述。认为不同的估算方法有其不同的适用条件和范围,在实际应用中需根据已有资料条件和研究的目的,选用不同的计算方法。  相似文献