Diagnosing stream ecosystem integrity in the Ordesa‐Viñamala Biosphere Reserve,central Spanish Pyrenees

This work studied the ecological integrity of river ecosystems inside the Ordesa‐Viñamala Biosphere Reserve in the central Spanish Pyrenees. Despite its protected status, the reserve endures a considerable number of human stresses, thus the aim was to evaluate the conservation status of the two river basins inside the protected area: The Gállego River Basin, inside the transition zone of the protected area and which allows a wide range of human activities; and the Ara River Basin, inside the buffer zone where only sound ecological practices are authorised. The environmental status of river ecosystems was analysed by studying fish and macroinvertebrate communities, hydrochemical and habitat characteristics and by calculating environmental quality indices. From August to September 2011, a total of 14 sites were sampled. Fish sampling was conducted using electrofishing gear, and macroinvertebrate were sampled by applying the IBMWP and IASPT procedures. Results showed that, while the Ara River Basin maintains a solid ecological integrity, the Gállego River Basin endures important habitat alteration. Trout, the dominant and exclusive species in the Ara River, were absent and replaced by translocated native cyprinids in the Gállego River Basin. This colonisation was explained by the alteration of the stream ecosystems and their homogenisation. The study of macroinvertebrate communities and the diagnosis obtained with the environmental quality indices also enhanced the deficient ecological integrity of some sites in the Gállego River. The results suggest that the Biosphere Reserve is not providing adequate protection to streams inside its boundaries, leading to major degradation of their biological integrity.     

Seasonal changes in habitat suitability for adult shovelnose sturgeon in the lower Mississippi River

Shovelnose sturgeon Scaphirhynchus platorynchus are a large‐river fish distributed throughout the Mississippi River basin, including the lower 1,533 km of the Mississippi River where riverine habitat has been and continues to be modified for navigation and is a potential site for development of instream hydrokinetic electric power generation. Information about habitat use and preference is essential to future conservation efforts. Shovelnose sturgeon have previously been found to select particular habitat types, and these selected habitats vary seasonally; although these past analyses do not consider the selected habitats in a landscape context. We used ecological niche factor analysis (ENFA) that uses distributions of telemetry locations and environmental variables to model habitat suitability in a landscape context. We recorded 333 locations of shovelnose sturgeon during July–December 2013 that included periods of relatively high and low river stages. The ENFA analysis indicated high‐suitability locations were in or near deep water during both high and low river stages. During high river stages, high‐suitability locations were near island tip habitat, deep water, and steep bottom slope and far from main channel habitat. During low stages, high‐suitability locations were in or near deep water and main channel habitat and far from secondary channel and wing dike habitats. This landscape‐scale analysis supports seasonal shifts in habitat use and provides insights that can be used to inform habitat conservation and management to benefit shovelnose sturgeon in the lower Mississippi River and possibly other large rivers.     

Fine‐scale habitat preferences influence within‐river population connectivity: a case‐study using two sympatric New Zealand Galaxias fish species

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A qualitative procedure for the assessment of the habitat integrity status of the Luvuvhu River (Limpopo system,South Africa)

The riparian zone and instream habitat integrity of the Luvuvhu River were assessed based on a qualitative rating of the impacts of major disturbance factors such as water abstraction, flow regulation, bed and channel modification, etc. A system was devised to assess the impact of these factors on the relative frequency and variability of habitats on a spatial and temporal scale gauged against habitat characteristics that could have been expected to occur under conditions not anthropogenically influenced. It was found that deterioration of habitat integrity can be ascribed primarily to water abstraction. This has resulted in the cessation of surface flow in a naturally perennial river during the dry season and during droughts with consequent tree deaths and a loss of fast flowing instream habitat types in the main stem of the river. The relatively small high rainfall area in the catchment, the highly variable rainfall pattern and the occurrence of sporadic severe droughts exacerbate the impact of water abstraction on the instream and riparian habitats with expected detrimental consequences for the associated biota. The effect of water abstraction is particularly severe in the lower part of the river which flows through the Kruger National Park as no perennial tributaries join the Luvuvhu River in this section. Other factors which affect the habitat integrity of the river are the removal of indigenous riparian vegetation in some river sections, encroachment by exotic vegetation, bank erosion and stream bed modification.     

Long‐term mark‐and‐recapture study of a freshwater mussel reveals patterns of habitat use and an association between survival and river discharge

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Young‐of‐the‐year (YOY) assemblage sampling as a tool for assessing the ecological quality of running waters

The aim of this study was to test young‐of‐the‐year (YOY) assemblage applicability for the ecological quality assessment on the basis of samples from 55 sites scattered across the entire Czech Republic. European Fish Index (EFI) values estimated with YOY and adults were positively correlated, indicating that YOY and adult sampling is comparable. YOY bias the EFI toward significantly lower values, however, adults also lead to underestimated EFI values on some occasions. Relative differences between EFI YOY and EFI adults show almost normal distributions and indicate that there is no detectable systematic bias caused by environmental conditions or intensity of sampling. As shown in the Elbe River example, the reason for lower EFI YOY values could be found in a longer period of detection of evident changes in adult fish assemblages, reflecting longevity of adult fishes or regular stocking. YOY sampling was suggested as a useful method for assessing river ecological quality, with the ability to provide a sensitive response to the habitat structure regardless of the effect of stocking or river size.     

Conceptual Evaluation of Factors Potentially Affecting Restoration of Habitat Structure within the Channelized Kissimmee River Ecosystem

A critical element of the ongoing effort to restore the ecological integrity of Florida's Kissimmee River ecosystem is the reestablishment of pre-channelization habitat structure and function. Restoration of habitat will form the basis for responses by most biological components of the ecosystem and will provide a key indicator of the success of the restoration effort. This paper evaluates the relative importance of a range of abiotic and biotic habitat parameters in the existing and historic Kissimmee River ecosystem and provides a conceptual framework for predicting expected spatial and temporal responses of river and floodplain habitats to the restoration project. Among the ecological factors and process that influenced the development, dynamics, and maintenance of river and floodplain habitat structure, hydrology is expected to be of central importance in eliciting restoration responses in the Kissimmee River Ecosystem. Based on the assumption that the restoration plan will reestablish historic hydrologic characteristics, predictions are made of expected responses by geomorphic and vegetative components of the Kissimmee River's habitat structure. Recommendations are made regarding key habitat parameters requiring long term tracking and analysis and utilization of a geographic information system(GIS). A hierarchical habitat classification scheme is provided as a foundation for all components of the restoration evaluation program.     

北京市白河和潮河流域生态健康评价

选取北京市重要的饮用水源密云水库上游白河和潮河流域,结合北京山区流域生态现状,构建了涵盖水域生境结构、水生生物、生态压力和陆域生态格局与功能、生态压力5大类13项指标的评价指标体系,开展了流域生态健康评价。结果表明白河和潮河流域的健康状态整体处于良好等级,但水生生物和陆域生态格局状况相对较差。14个子流域的健康状况差异并不显著,琉璃河、白河下段、汤河上游的健康状况相对较好,潮河中下段和小汤河的健康状况相对较差。流域内不合理的畜禽养殖、岸边带种植及民俗旅游是导致流域生态健康退化的主要原因,建议加强污染负荷排放的控制和监管涉水活动对水生生境的干扰以改善流域健康状况,并重点关注可指示水生态系统早期退化的生物指数,以实现可持续性和适应性的流域管理,保障密云水库的水生态安全。     

Influence of fine‐scale habitat requirements and riparian degradation on the distribution of the purple‐crowned fairy‐wren (Malurus coronatus coronatus) in northern Australia

Species distributions are influenced by variation in environmental conditions across many scales. Knowledge of fine‐scale habitat requirements is important for predicting species occurrence and identifying suitable habitat for target species. Here we investigate the perplexing distribution of a riparian habitat specialist, the western subspecies of the purple‐crowned fairy‐wren (Malurus coronatus coronatus), in relation to fine‐scale habitat associations and patterns of riparian degradation. Surveys of vegetation attributes, river structure and disturbance indicators that are likely to be causal determinants of the species occurrence were undertaken at 635 sites across 14 catchments. Generalized Linear Mixed Modelling demonstrated that the probability of purple‐crowned fairy‐wren occurrence increased with Pandanus aquaticus crown cover, shrub density and height of emergent trees, while riparian structure and signs of cattle were indirect predictors of occurrence. As our study area predominantly contained Pandanus type habitat, we failed to identify river grass as an important component of habitat. Predictions from a cross‐validated model of purple‐crowned fairy‐wren occurrence suggested distribution is constrained by three factors: (i) low quality of local habitat within catchments where the species occurs; (ii) broad‐scale reduction in habitat quality that has resulted in extinction of the species from parts of its range; and (iii) unmeasured variables that limit the exploitation of suitable habitat. The reliance of the species on dense shrubby understorey suggests conservation efforts should aim to maintain the complexity of understorey structure by managing fire and grazing intensity. Efforts to halt the continuing decline of riparian condition and maintain connectivity between areas of quality habitat will help to ensure persistence of riparian habitat specialists in northern Australia.     

Large‐scale,long‐term trends in British river macroinvertebrates

Rivers are among the world's most modified ecosystems, with poor water quality representing a prominent problem for over 200 years, especially in urban areas. In Western Europe, however, industrial decline, tighter regulation and improved wastewater treatment have combined over recent decades to create conditions conducive to extensive restoration and positive biological change. Here, we evaluate the river macroinvertebrate fauna of England and Wales in relation to water quality, physical habitat and climate over almost two decades. We predicted that biological recovery would be characterized by: (i) greater taxon richness and prevalence of pollution‐sensitive taxa, (ii) larger changes in more heavily urbanized catchments, and (iii) temporal trends in assemblage structure that correlated with improving water quality. Family level richness increased on average by nearly 20% during 1991–2008, accompanied by a widespread shift towards taxa characteristic of well‐oxygenated and less polluted waters. Changes were largest in the most urbanized catchments. A combination of natural gradients and anthropogenic pressures explained the variation among sites, whereas temporal changes correlated with improving water quality and variations in discharge. Positive trends were not universal, however, and there was localized deterioration in some streams draining upland areas and in the lowland south east. Our results are consistent with a large‐scale ecological recovery of English and Welsh rivers since 1990, probably continuing a trend from the mid‐20th century. Based on these results, we suggest: (i) freshwater communities are resilient to long‐term anthropogenic pressures, (ii) biodiversity benefits can arise from investment and long‐term restoration intended largely to enhance ecosystem services such as drinking water and sanitary concerns, and (iii) long‐term monitoring data collected for statutory purposes–based in this case on nearly 50 000 samples–can address scientific questions at spatial and temporal extents seldom achieved in research programmes.     

The influence of dams on ecohydrological conditions in the Huaihe River basin, China

Maintaining natural hydrologic variability is essential in conserving native riverine biota and river ecosystem integrity. Hydrologic regimes play a major role in structuring the biotic diversity within river ecosystems, as they control key habitat conditions within the river channel, the floodplain, etc. Alterations in streamflow regimes may modify many of these habitat attributes and impair ecosystem connectivity. There are many dams constructed in the Huaihe River basin that are drastically altering the natural hydrologic regimes of the river. We selected the Bengbu Sluice as a control node to study the influence of the Bengbu Sluice and all its upstream dams on the hydrologic regime. Using Indicators of Hydrologic Alteration and Range of Variability Approach methods, we assessed hydrologic alteration at the streamgauge site to demonstrate the influence of dams on ecohydrological conditions in the Huaihe River basin. The results show that dams have a strong influence on ecohydrological conditions, especially in dry seasons. The river ecohydrological targets and the minimum ecological and environmental flow requirements for the Bengbu section defined by this study can support ecosystem management and restoration plans and provide ecological operations for the Bengbu Sluice.     

Habitat‐specific invertebrate responses to hydrological variability,anthropogenic flow alterations,and hydraulic conditions

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Assessing the quality of four inshore habitats used by post yolk‐sac Alosa sapidissima (Wilson 1811) in the Hudson River: a prelude to restoration

Habitat restoration within large rivers to enhance early life stages of fish is an emerging field. Prior to restoration, assessment of what constitutes “good” habitat is needed. We exemplify this with a study of larval Alosa sapidissima (American shad) in the Hudson River estuary in New York State, United States, which examines the quality of four main shallow water habitat types that have been reduced greatly by dredging activities. The larval stage has been identified as a sensitive period in need of mortality reduction. Habitats were examined as nursery habitat by comparing ambient conditions to known suitability indexes and by comparing relative abundance, loss rate, daily growth, and relative condition among habitats. Areas of lower velocity had greater abundances of shad ≤15.0 mm in length and shad growth was significantly higher. As shad became larger, those in areas of higher velocity had significantly higher relative condition, suggesting a shift in habitat use as larvae metamorphose into the juvenile stage. Contiguous backwater and secondary channel habitats had reduced loss rates during 2011 when there was high river discharge. No single habitat type examined in this study was found to be overall poor quality, and it is recommended that restoration sites be examined on an individual basis. More broadly, habitat diversity appears needed both for within‐year ontogeny as well as for longer‐term resiliency in the face of disturbance, such as storm‐driven high flows.     

Applying non-metric multidimensional scaling analysis for measuring the assemblage change of Chu-Lan Creek dike in Taiwan

Ensuring that water resources development in harmony with aquatic environment is the major water policy of Taiwan in the 21st century, Taiwan's water authority has adopted several methodologies, such as utilizing ecological engineering techniques, establishing integrated water resources management configuration, involving the public in decision-making processes, etc., and applying them in the field. Significant consequences in ecological engineering were obtained in several cases, such as for Ta-Chia Creek, where wire cages, tires, and boulders were installed to improve the stream habitat, and for Wu-Lao Creek, where natural water purification facilities were constructed to reduce river pollution. Although the sustainable methodologies have been widely accepted by hydraulic engineers in Taiwan, lack of engineer-friendly evaluation indices or methods hindered the further progress of river ecological engineering projects. This research applied a non-metric multidimensional–scaling (MDS) analysis to measure the assemblage change of river aquatic habitat. A dike construction project at Chu-Lan Creek was selected for verification in this study. The analyzed results showed that the dike construction project did affect the aquatic habitat in Chu-Lan Creek. The proposed MDS analysis successfully captured the effect of the construction. The MDS method could be used to evaluate the improvement or damage of aquatic habitat by a traditional hydraulic approach or a new ecological hydraulic developed technique in Taiwan.     

Genetic population structure in prickly sculpin (Cottus asper) reflects isolation‐by‐environment between two life‐history ecotypes

Life‐history transitions have evolved repeatedly in numerous taxa, although the ecological and evolutionary conditions favouring such transitions in the presence of gene flow remain poorly understood. The present study aimed to disentangle the effects of isolation‐by‐distance and isolation‐by‐environment on genetic differentiation between two sympatric life‐history ecotypes. Using 14 microsatellite loci, we first characterized amphidromous and freshwater groups of Cottus asper in a high gene flow setting in the Lower Fraser River system (south‐western British Columbia, Canada) to test for the effects of habitat and geographical distance on the distribution of life‐history ecotypes. Within the main river channel, no genetic differentiation was found, whereas tributaries even close to the estuary were genetically differentiated. Partial mantel tests confirmed that genetic differentiation between river tributaries and the main channel was independent from geographical distance, with distance‐scaled migration rates indicating reduced gene flow from the main channel into the tributaries. Our results suggest that isolation‐by‐environment can play an important role for the early stage of life‐history transitions, and may promote differentiation among life‐history ecotypes despite the presence of gene flow. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 943–957.     

Spatiotemporal patterns and habitat associations of smallmouth bass (Micropterus dolomieu) invading salmon‐rearing habitat

1. Smallmouth bass (Micropterus dolomieu) have been widely introduced to fresh waters throughout the world to promote recreational fishing opportunities. In the Pacific Northwest (U.S.A.), upstream range expansions of predatory bass, especially into subyearling salmon‐rearing grounds, are of increasing conservation concern, yet have received little scientific inquiry. Understanding the habitat characteristics that influence bass distribution and the timing and extent of bass and salmon overlap will facilitate the development of management strategies that mitigate potential ecological impacts of bass. 2. We employed a spatially continuous sampling design to determine the extent of bass and subyearling Chinook salmon (Oncorhynchus tshawytscha) sympatry in the North Fork John Day River (NFJDR), a free‐flowing river system in the Columbia River Basin that contains an upstream expanding population of non‐native bass. Extensive (i.e. 53 km) surveys were conducted over 2 years and during an early and late summer period of each year, because these seasons provide a strong contrast in the river’s water temperature and flow condition. Classification and regression trees were applied to determine the primary habitat correlates of bass abundance at reach and channel‐unit scales. 3. Our study revealed that bass seasonally occupy up to 22% of the length of the mainstem NFJDR where subyearling Chinook salmon occur, and the primary period of sympatry between these species was in the early summer and not during peak water temperatures in late summer. Where these species co‐occurred, bass occupied 60–76% of channel units used by subyearling Chinook salmon in the early summer and 28–46% of the channel units they occupied in the late summer. Because these rearing salmon were well below the gape limitation of bass, this overlap could result in either direct predation or sublethal effects of bass on subyearling Chinook salmon. The upstream extent of bass increased 10–23 km (2009 and 2010, respectively) as stream temperatures seasonally warmed, but subyearling Chinook salmon were also found farther upstream during this time. 4. Our multiscale analysis suggests that bass were selecting habitat based on antecedent thermal history at a broad scale, and if satisfactory temperature conditions were met, mesoscale habitat features (i.e. channel‐unit type and depth) played an additional role in determining bass abundance. The upstream extent of bass in the late summer corresponded to a high‐gradient geomorphic discontinuity in the NFJDR, which probably hindered further upstream movements of bass. The habitat determinants and upstream extent of bass were largely consistent across years, despite marked differences in the magnitude and timing of spring peak flows prior to bass spawning. 5. The overriding influence of water temperature on smallmouth bass distribution suggests that managers may be able limit future upstream range expansions of bass into salmon‐rearing habitat by concentrating on restoration activities that mitigate climate‐ or land‐use‐related stream warming. These management activities could be prioritised to capitalise on survival bottlenecks in the life history of bass and spatially focused on landscape knick points such as high‐gradient discontinuities to discourage further upstream movements of bass.     

Long‐term change to fish assemblages and the flow regime in a southeastern U.S. river system after extensive aquatic ecosystem fragmentation

The upper Tombigbee River in northeastern Mississippi now exists as a fragment, confluencing with and fed by an extensively modified aquatic landscape now called the Tennessee‐Tombigbee Waterway (TTW). We examined the changes to fish assemblages and flow regime after waterway construction based on contemporary comparisons to historical fish collections and discharge data. The river's flow regime has changed markedly since TTW construction. Analysis of discharge data from two stations for 15 years, pre‐ and post‐waterway, indicated significant differences in flow regime including increased minimum and base flows, lower spring and higher late summer‐autumn flows, and lower high flow durations, post‐TTW. These changes corresponded to significantly reduced regional and local species richness, and strong shifts in fish assemblage structure across a 20 yr time span. Post‐waterway fish assemblages were related strongly to measured environmental variables characterizing local habitats. Several lentic‐adapted species increased their abundances in lower reaches of the river, including a recent invader to the TTW system, the Mississippi silverside Menidia audens. Fragmentation of river ecosystems via disruption to hydrologic regimes is a major threat to aquatic biodiversity worldwide. Because the flow regime of this fragmented river is in part controlled by waterway operations via five minimum flow control structures, adaptive conservation and management efforts could be implemented in order to maintain and potentially restore the natural flow regime and the ecological integrity of the system.     

Direct and indirect effects of predatory young‐of‐year fishes in a dryland river food web

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海河流域河流生境功能识别及区域差异

城市群快速发展严重影响着区域水生态系统的完整性,大尺度流域的河流生境功能辨识和分析尚缺乏系统研究。以海河流域为例,根据河段蜿蜒度、河段比降、断流风险、盐度等4个指标,构建了河流生境功能的分类指标体系。通过多源空间数据和人工判读,划分了6254条河段,在此基础上将河流生境类型划分为15类。通过52个监测样点的鱼类调查数据,分析了不同河流生境的水生生物特征差异,揭示了鱼类多样性高的区域多位于河流比降大、断流风险低的区域,而河流蜿蜒度对于鱼类多样性影响较小。根据京津冀13个地级市的河流生境差异,提出京津冀城市群的生态安全构建需要充分考虑河流生境的空间异质性,并制定融合城市发展目标、水资源利用需求和河流生境功能的综合指标体系。     

Fish community changes after minimum flow increase: testing quantitative predictions in the Rhône River at Pierre-Bénite, France

1. Many aspects of the flow regime influence the structure of stream communities, among which the minimum discharge left in rivers has received particular attention. However, instream habitat models predicting the ecological impacts of discharge management often lack biological validation and spatial generality, particularly for large rivers with many fish species. 2. The minimum flow at Pierre‐Bénite, a reach of the Rhône river bypassed by artificial channels, was increased from 10 to 100 m³ s^?1 in August 2000 (natural mean discharge 1030 m³ s^?1), resulting in a fivefold increase in average velocity at minimum flow. Fish were electrofished in several habitat units on 12 surveys between 1995 and 2004. 3. Principal components analysis revealed a significant change in the relative abundance of fish species. The relative abundance of species preferring fast‐flowing and/or deep microhabitats increased from two‐ to fourfold after minimum flow increase. A change in community structure confirmed independent quantitative predictions of an instream habitat model. This change was significantly linked to minimum flow increase, but not to any other environmental variables describing high flows or temperature at key periods of fish life cycle. The rapidity of the fish response compared with the lifespan of individual species can be explained by a differential response of specific size classes. 4. The fish community at Pierre‐Bénite is in a transitional stage and only continued monitoring will indicate if the observed shift in community structure is perennial. We expect that our case study will be compared with other predictive tests of the impacts of flow restoration in large rivers, in the Rhône catchment and elsewhere.