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   27篇
  免费   11篇
  国内免费   4篇
林业   1篇
农学   2篇
  3篇
综合类   6篇
水产渔业   28篇
畜牧兽医   2篇
  2023年   2篇
  2022年   1篇
  2021年   3篇
  2019年   4篇
  2018年   3篇
  2017年   3篇
  2016年   4篇
  2015年   2篇
  2014年   2篇
  2013年   2篇
  2012年   2篇
  2011年   2篇
  2010年   3篇
  2009年   2篇
  2008年   2篇
  2007年   2篇
  2006年   1篇
  2002年   1篇
  2000年   1篇
排序方式: 共有42条查询结果,搜索用时 15 毫秒
1.
The diversity, distribution and species richness of benthic macroinvertebrate fauna as well as benthic environments were examined in the blood cockle Anadara granosa cultivations at Ban Don Bay, Suratthani Province, Southern Thailand during the summer season of April and rainy season of October in 2017. The cockle cultivations of three repeated operating ages (<5 years: S1; 5–10 years: S2; more than 10 years: S3) were selected for the study, and the sampling sites were allocated at the centre of the farm. Results indicated that there were significant differences in species number, individual number and evenness index of benthic macroinvertebrate fauna found in the two sampling seasons (p < .05) and significant differences in individual number and evenness index were found among the sampling sites (p < .05). Significant differences in pH, total phosphorus levels, sulphide levels and organic matter of sediment were found between the sampling seasons (p < .05) and differences in total nitrogen level, organic matter and clay content were found among the sampling sites (p < .05). Among the independent variables analysed, correlation analysis showed no relationship between diversity index, species richness index and evenness index and the abiotic variables (p < .05). The results of the present study suggest that the distribution and diversity variations of the benthic macroinvertebrates community fauna are not affected by all sediment parameters in various repeated cultivation of the blood cockle Anadara granosa in Bandon Bay, Suratthani Province.  相似文献   
2.
  1. The Calapooia River in western Oregon supports a small winter steelhead trout (Oncorhynchus mykiss) population and historically supported spring Chinook salmon (Oncorhynchus tshawytscha). Early timber harvesting removed the riparian forest, and log transportation practices simplified the channel. Those disturbance legacies continue to affect fish habitat by limiting shade and channel complexity, complicating conservation efforts.
  2. To evaluate juvenile salmonid rearing potential, macroinvertebrate drift, thermal regime and physical habitat were measured at eight sites in 24 km of the upper river during late summer baseflow.
  3. Overall physical habitat was simple, with few functioning instream structures or pools. During the 22‐day drift study, flows declined and maximum site stream temperatures ranged from 23.1°C at the lower end to 16.4°C 24 km upstream.
  4. Macroinvertebrate drift concentrations ranged from 0.7–13.7 ind. m?3 with biomasses from 0.02–1.23 mg m?3. Drift concentration biomass was higher upstream (P  = 0.006) than downstream and declined overall (P  < 0.001) during the study. Drift biomass was dominated by five taxon groups – Baetis tricaudatus, Calineuria californica, Hesperoperla pacifica, Simulium spp., and Chironomidae, which were 65% of total biomass. During twilight, total biomass and biomass of B. tricaudatus, Simulium spp., and Chironomidae (both larvae and adults) were higher.
  5. Total drift declined dramatically over the study period owing to decreases in drift concentration and a 58% decline in discharge, greatly reducing overall drift and available food resources for juvenile‐rearing salmonids.
  6. The upper catchment, both with cooler temperatures and higher food availability, provided the best conditions for juvenile anadromous salmonids to survive late summer conditions. Conservation consequences of climate change‐induced alterations in flow and temperature may further affect habitat quality for juvenile salmonids in this catchment in the coming decades.
  相似文献   
3.
湟水河上游大型底栖动物多样性及水体理化因子调查分析   总被引:1,自引:1,他引:0  
为研究青藏高原农牧交错地带水生生物与环境指标的关系,于2015年5月(枯水季)和8月(丰水季),调查分析了湟水河上游47个样点水体的理化指标和大型无脊椎底栖动物。水体物理指标现场采用多参数水质检测仪和FP311杆式流速仪检测;采集水样带回实验室测定化学指标,总氮和总磷采用过硫酸钾氧化紫外分光光度法测定;NH4+-N含量采用纳氏试剂光度法测定。底栖动物采用索伯网和D形网采集。结果显示:支流各项理化指标数据均优于干流,尤其以浊度、细砂淤泥比例、NH4+-N、TN和TP最为显著。底栖动物共鉴定出28科57属59种,其中昆虫纲7目54种,占所有底栖动物种类的91.5%,个体数4444头,占所有底栖动物数量的76.4%,甲壳纲、软体动物类、寡毛类等底栖动物个体数占底栖动物总量的23.6%。湟水河上游支流底栖动物平均分类单元数(6.76)基本与干流相当(8.04),对水质敏感的EPT平均分类单元数支流(3.36)也与干流相当(2.48),但干流底栖动物耐污染种类比例明显高于支流,而支流敏感种类比例明显高于干流。从底栖动物群落结构和水体理化指标来看,湟水河上游支流总体优于干流,其差异源于干流受污染较重。  相似文献   
4.
在剑湖选择11个采样点,于2011年1月、4月、6月和10月按季度4次对大型底栖动物进行采样调查,共发现大型底栖动物52种,主要为软体动物、水生昆虫和环节动物种类。大型底栖动物的密度和生物量时空分布差异明显,密度表现为冬季>春季>夏季>秋季;生物量表现为夏季>春季>秋季>冬季。各采样点全年密度为16~23840个/m2,最高密度出现在采样点A左,最低密度则在采样点E右;生物量全年为1.68~2343.47 g/m2,以采样点D最高,采样点I最低。Margalef丰富度指数全年为0.10~2.75,最高值出现在秋季,最低值出现在夏季;Shannon -Wiener 指数、Simpson生物指数和Pielou均匀度指数全年分别为0.09~1.09、0.03~0.65和0.03~1.43,最高值均出现在夏季,最低值均出现在冬季。  相似文献   
5.
为研究不同水位时期大宁河底栖动物群落的结构特征及其差异,于2011-2013年间分别在三峡水库低水位期(145 m)和高水位期(170 m)对大宁河的底栖动物进行定性和定量调查。低水位期生物密度和生物量分别为(80.32±32.14)ind./m2和(1.44±0.45)g/m2,高水位期生物密度和生物量分别为(133.82±46.94)ind./m2和(1.53±0.51)g/m2。寡毛类在静水区域占优势,水生昆虫在流水区域占优势。底栖动物物种组成和分布表现为高水位期高于低水位期,流水区域显著高于静水区;不同水位时期生物密度和生物量差异显著,优势种及其相对丰度有较大波动;生物多样性表现为高水位期高于低水位期,流水区域显著高于静水区。聚类分析和多维尺度分析结果显示,大宁河底栖动物群落结构在时间上和空间上均出现了明显的分化。  相似文献   
6.
三横山人工鱼礁区鱼类和大型无脊椎动物诱集效果初探   总被引:12,自引:6,他引:6  
汪振华  章守宇  王凯  赵静  许敏 《水产学报》2010,34(5):751-759
为了解人工鱼礁投放对鱼类和大型无脊椎动物(简称FM,以下同)的诱集效果,分别于2007年5、9月和2009年3、5、7月对上三横山人工鱼礁B区与泥底区进行了拖网本底和跟踪调查,并于2009年1-8月对下三横山人工鱼礁A区与鳗头山岩礁和泥底区进行了刺网调查。采用CPUE、Margalef种类丰富度d、经济种类数变化、Whilm多样性指数H′′等反映FM的资源状况。结果显示,(1)鱼礁A区和岩礁区在CPUE、种类丰富度、经济种和多样性上均无明显差异(P>0.05),而两者各指标与泥底区皆存在显著差异(P<0.05);(2)鱼礁B区,投礁后CPUE和经济种类数都明显高于投礁前也大于同期对照区,差异显著(P<0.05);礁区平均丰富度水平高出同期对照区31.1%(P<0.05);多样性水平相对投礁前和对照区都有一定提高,但尚无显著差异(0.05相似文献   
7.
Indigenous soil macroinvertebrates (moth larvae, weevil larvae, earthworms) are cardinal agents of nutrient release from litter on sub-Antarctic Marion Island (47°S, 38°′E). Their populations are threatened through predation by introduced house mice, which do not prey on an introduced slug Deroceras panormitanum. A microcosm study was carried out to explore whether slugs affect rates of carbon and inorganic nutrient mineralisation from plant litter differently to an indigenous caterpillar (larva of a flightless moth Pringelophaga marioni). Caterpillars stimulated N, Ca, Mg and K mineralisation from plant litter two to five times more than slugs did, whereas the two invertebrate types stimulated C and P mineralisation to the same degree. Consequently, ratios of C:N and N:P released from the litter were different for slugs and caterpillars. Such differences might affect peat nutrient quality and ultimately the peat accumulation-decomposition balance, an important driver of ecological succession. This suggests that slugs cannot simply replace caterpillars without consequences for ecosystem structure and functioning on the island.  相似文献   
8.
  • 1. Many rivers and streams across the world have been channelized for various purposes. Channel cross‐sections of meandering rivers are asymmetrical and have cross‐sectional diversity in their physical environment; cross‐sections of a channelized river are typically trapezoidal and have little cross‐sectional diversity, both in physical and ecological conditions. Several programmes to restore stream meanders have been undertaken to improve river ecosystems degraded by channelization. However, the association between diversification in the physical environment due to meander restoration and the macroinvertebrate community structure is poorly known.
  • 2. This study of a lowland river in Japan assessed how the cross‐sectional diversity of the physical environment changed with restoration of a meander in a channelized river, and how the macroinvertebrate communities responded to the changes in physical habitat variation. Comparisons were made between the macroinvertebrate communities of a channelized reach, the restored meandering reach, and a natural meandering reach.
  • 3. Natural meandering and restored meandering reaches showed higher cross‐sectional diversity in physical variables and total taxon richness across a reach than did the channelized reach. Almost all taxa observed in the natural and restored meandering reaches were concentrated in the shallowest marginal habitats near the banks. Shear velocity increasing with water depth had a negative association with macroinvertebrate density and richness.
  • 4. This study demonstrated that the shallow river bed along the inside of bends formed point bars that provided a highly stable substrate, a suitable habitat for macroinvertebrates in a lowland river. It is concluded that meander restoration could be an effective strategy for in‐stream habitat restoration in lowland meandering rivers.
Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
9.
  • 1. The River Styles® framework is a geomorphic approach to the classification of river types, assessment of the physical condition of rivers, and planning of physical rehabilitation. However, the linkages between River Styles and aquatic biodiversity conservation are still only weakly developed.
  • 2. In this study, 41 sites in the Bega River basin in New South Wales, Australia, were classified according to River Style and geomorphic condition, and surveyed for four biological assemblages: diatoms, aquatic and semi‐aquatic macrophytes, aquatic macroinvertebrates and fish.
  • 3. Each assemblage differed significantly among River Styles. However, in the case of diatoms and fish, these differences could be accounted for by geographic clustering of sites in the same River Style, and a tendency for River Styles to occupy particular altitudinal zones and sizes of streams. This result was attributed to the overriding influences of water quality on diatoms and of altitude‐related variation in water temperature and distance from the ocean on fish. For macrophytes and macroinvertebrates, geomorphic river type appeared to exert a direct influence, probably via variation in physical habitat characteristics.
  • 4. Geomorphic condition, judged as good, moderate or poor by reference to the inferred natural condition of each River Style, was also significantly associated with differences in biological assemblages other than fish. Twice as many taxa appeared to favour sites in good geomorphic condition as favoured sites in poor condition. Many of the taxa associated with sites in poor condition are alien taxa introduced to Australia since European settlement.
  • 5. These findings imply that protection of reaches that are in good geomorphic condition is likely to be critical for the maintenance of indigenous biodiversity, and that rehabilitation of geomorphic condition can assist in the rehabilitation of native riverine biota.
Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
10.
Rapidly expanding water resource development in arid and semi-arid zones of Australia threatens the flow regime and ecological integrity of the few large dryland rivers and their immense floodplains. Efforts to manage and conserve the surface waters of these rivers are hampered by limited scientific data on the ecology of their flora and fauna and on their responses to the high natural variability of flow regime that typifies dryland rivers. Irregular floods connect channel and floodplain wetlands to differing degrees and for varying periods of time but the ecological significance of this connectivity is poorly understood. On Cooper Creek, a large dryland river in central Australia, we explored the degree to which assemblage composition varied with connectivity and hydrological regime. Shortly after protracted regional flooding, we sampled aquatic macroinvertebrate assemblages from the principal microhabitats in 12 channel and floodplain wetlands. Ephemeral and temporary lakes tended to have fewer taxa than semi-permanent channel or terminal lake habitats. Although hydrological connection had only recently been lost for some wetlands, there was already evidence of divergence in aquatic macroinvertebrate assemblage composition. Disruption of the natural variability in connectivity and hydrological regime by excessive water abstraction or river-flow regulation threatens the ecological integrity and aquatic macroinvertebrate biodiversity of dryland rivers. Preservation of the irregular flow regime and sporadic connectivity underpins conservation of the mosaic of floodplain wetlands that play such a crucial role in the ecosystem functioning of rivers such as Cooper Creek.  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