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1.
Blue sucker Cycleptus elongatus (L.) in the upper Yazoo River basin, Mississippi, USA was studied using overnight hoop net sets (n = 4093) during 1988 and 1990–1998 to determine the influence of channel dredging. There were 264 blue suckers captured, ranging from 3 to 11 years of age. Length ranged from 265 to 700 mm and weight from 120 to 4700 g. Concurrent studies with smaller mesh hoop nets failed to capture any juvenile blue suckers. Catch‐per‐unit‐effort (CPUE: fish net?1) declined throughout the study in the Yalobusha River, a river subjected to channel dredging during 1988 and 1994. With the exception of limited hydraulic dredging in the Tallahatchie River, there was no dredging in the other Yazoo River tributaries, nor were there declines in blue sucker catch rates in these rivers. Throughout the upper Yazoo River basin, blue sucker stocks were dominated by adult fish, and there was little evidence of reproduction or recruitment. Conservation of the blue sucker in the upper Yazoo River basin should include actions that ensure the functional integrity of this floodplain river ecosystem and elimination of channel dredging throughout the basin. 相似文献
2.
- Extensive assessments of a species distribution, its variation in density and demographic status across environments are crucial to develop successful conservation efforts.
- The freshwater pearl mussel (Margaritifera margaritifera) is considered one of the most endangered freshwater bivalves with many recovery efforts continuing throughout its geographic range. The distribution and conservation status of M. margaritifera are not well documented in the Iberian Peninsula. Galicia (NW Iberian Peninsula) represents nearly 70% of the historical distribution of the species in the southern limit of its European range.
- An extensive field survey was conducted in two phases at 2436 locations. The presence and density of M. margaritifera was determined at 555 sampling points spread across 54 rivers that belong to 23 drainage basins in Galicia. The present work has more than doubled the number of rivers known to provide habitat for this endangered species in the Iberian Peninsula.
- In Galicia the species is heterogeneously distributed with a highly variable density of individuals within and between rivers. For example, within the River Camba density ranged from 0.02 to 47.8 ind m‐2. The maximum density detected in a sample was 332 ind m‐2. Twelve rivers in Galicia are thought to have more than 5000 individuals, and small individuals were found in 11 rivers.
- High rates of decline and extinction of M. margaritifera populations are known in some areas and the main threat to unionoid bivalves is a lack of natural recruitment. Thus, Galician populations are important for providing new opportunities for conservation of the species in Europe because it is vitally important to find the reasons for recruitment failure.
3.
研究分析了丁坝和护坦在沿河林区公路路基防护中的作用、防护原理、设置方法、应用条件和有效性问题。 相似文献
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河流生态景观是旅游业发展的重要资源。人类长期的过度开发,导致河流生态系统严重退化。针对淇河生态系统退化现状,提出以科学的人地观来协调生态环境与经济发展间的关系,并以景观生态学为理论基础指导旅游开发、生态系统的恢复重建,从而很好地实现“人河和谐”可持续发展。 相似文献
6.
沙土区薄壁连拱护岸墙为悬臂式支撑、薄壁连拱无底板结构,拱板中间采用无砂砼排水孔的钢筋砼肋形预制板,冲沉法施工,造价低廉;外形美观,抗倾、抗滑性能强。该墙为平原沙土区河道水土保持及修复找到了一条经济合理、施工方便、简便易行的护坡办法,具有较高的实用价值和广阔的推广使用前景。 相似文献
7.
针对引黄济津应急调水工程河北段的输水能力进行了研究。渠段的输水能力是指渠段所能通过的最大入流量，即渠段的首端断面所能通过的最大流量。根据引黄济津应急调水工程近4年的实测数据，构建了适于干河床水流推进过程渗漏损失的改进模型、小水深情况下的糙率加大模型，并采用均匀试验优选方法对水力参数进行了反演，利用非恒定流模型对引黄济津河北段渠系输水能力进行了计算。结果表明，建立的渗漏损失改进模型、小水深情况下的糙率加大模型是合理的，反演得到的参数是精确的；由于在水流推进与涨水阶段渠床的非稳定渗漏起了较大作用，所以各渠段的输水能力在非稳定输水阶段比稳定输水阶段稍大。输水能力的计算结果可以为引黄济津未来几年的输水规划与调度提供具体的指导。 相似文献
8.
Jeanne L. Nel Dirk J. Roux Robin Abell Peter J. Ashton Richard M. Cowling Jonathan V. Higgins Michele Thieme Joshua H. Viers 《水产资源保护:海洋与淡水生态系统》2009,19(4):474-485
- 1. Freshwater ecosystems and their associated biota are among the most endangered in the world. This, combined with escalating human pressure on water resources, demands that urgent measures be taken to conserve freshwater ecosystems and the services they provide. Systematic conservation planning provides a strategic and scientifically defensible framework for doing this.
- 2. Pioneered in the terrestrial realm, there has been some scepticism associated with the applicability of systematic approaches to freshwater conservation planning. Recent studies, however, indicate that it is possible to apply overarching systematic conservation planning goals to the freshwater realm although the specific methods for achieving these will differ, particularly in relation to the strong connectivity inherent to most freshwater systems.
- 3. Progress has been made in establishing surrogates that depict freshwater biodiversity and ecological integrity, developing complementarity‐based algorithms that incorporate directional connectivity, and designing freshwater conservation area networks that take cognizance of both connectivity and implementation practicalities.
- 4. Key research priorities include increased impetus on planning for non‐riverine freshwater systems; evaluating the effectiveness of freshwater biodiversity surrogates; establishing scientifically defensible conservation targets; developing complementarity‐based algorithms that simultaneously consider connectivity issues for both lentic and lotic water bodies; developing integrated conservation plans across freshwater, terrestrial and marine realms; incorporating uncertainty and dynamic threats into freshwater conservation planning; collection and collation of scale‐appropriate primary data; and building an evidence‐base to support improved implementation of freshwater conservation plans.
9.
近年来,因干旱少雨等自然灾害影响及人类生产活动对环境的破坏,致使一些中小河流生态功能遭到不同程度的破坏。结合沈阳市近年来河流生态建设的实施情况,从工程措施和生物措施两方面详细介绍了针对不同河流状况的生态建设措施,对今后类似工程建设提供借鉴。 相似文献
10.