Fish Associations among Un‐notched,Notched and L‐head Dikes in the Middle Mississippi River

Wing dikes and other anthropogenic modifications have heavily altered riverine ecosystems. Recent efforts to reach a compromise between the needs of the river transportation industry and natural resource conservation include dike modification. Dike notching permits water flow through the landward portion of the dike and has been purported to provide suitable habitat for fish and other river biota while maintaining the navigation channel. L‐head dikes are flow‐control structures that create calm backwater‐like habitats downstream. However, few researchers have examined the actual effects of dike notching on water quality or fish communities. We compared standardized catch per unit effort and overall community structure for 50 fish species among un‐notched dikes, notched dikes and L‐head dikes in the Middle Mississippi River, sampled as part of the US Geological Survey's Long‐Term Resource Monitoring Program. There were no differences in standardized catch per unit effort for 64% of the fishes examined. Five species known to be associated with lotic habitats were most abundant near L‐head dikes. Seven species were more abundant at un‐notched dikes than notched dikes, while six species were more abundant at notched dikes than un‐notched dikes. Non‐metric multidimensional scaling suggested differences in overall fish community structure between un‐notched and other dike types. Detailed physical habitat studies should be conducted to better understand the effects of dike modification. Copyright © 2015 John Wiley & Sons, Ltd.     

The Importance of Shallow‐Low Velocity Habitats to Juvenile Fish in the Middle Mississippi River

Habitat management is a crucial aspect of fisheries management. Without knowledge of habitat associations, fisheries scientists are unable to effectively make habitat conservation or restoration recommendations. This becomes especially prominent when trying to manage commercially harvested populations and protect threatened or endangered species. To determine juvenile fishes habitat associations in the Middle Mississippi River, we analysed mini‐trawl catch data of six common juvenile fish species: blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), channel shiner (Notropis wickliffi), freshwater drum (Aplodinotus grunniens), paddlefish (Polyodon spathula), and shovelnose sturgeon (Scaphirhynchus platorynchus). Overall, we conducted 2251 mini‐trawl sampling efforts between 2002 and 2013, resulting in the capture of 23,742 target specimens. Catch per unit effort was evaluated by structural habitat (i.e. velocity, depth, and substrate). Overall, these data suggest that juvenile fish species are more prevalent in shallow water and slower velocities. Ultimately the information garnered during this evaluation should be incorporated when considering habitat modifications, especially those modifications that impact the availability of shallow‐low velocity habitats. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of a high‐head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.     

Spatial patterns of fish communities in the Upper Mississippi River System: assessing fragmentation by low‐head dams

We assessed the similarity of fish communities among river reaches to assess community‐level fragmentation by low‐head dams in the Upper Mississippi River System (UMRS). The spatial coverage of standardized electrofishing sampling used in the Long Term Resource Monitoring Program (LTRMP) was extended for three of the six regional trend areas (RTA; pools 4, 13, and the Open River Reach) to include river reaches (outpools) immediately upstream and downstream from the standard RTA from 15 June to 31 October 2000. Additionally, pools 19 and 20 were sampled in September 2000. Cluster analysis and non‐metric multidimensional scaling of community composition and structure data revealed two major groups, upper and lower reaches, and four (for composition) or five (for structure) sub‐groupings of river reaches. In general, all outpools grouped with the nearest RTA for both community composition (no exception) and community structure (one exception). This suggests that fragmentation of fish communities from low‐head dams is minimal. Mantel correlations demonstrated strong inverse association between the similarity of fish communities with the distance between reaches. Habitat variables measured during electrofishing collections were significantly correlated with spatial variation of fish composition and community structure, but provided only marginal improvements to correlations with distance between reaches alone. Furthermore, habitat variability among river reaches also was related to distance between reaches. Determining the extent to which variation of fish communities is related to habitat or demographic processes (e.g. migration, larval drift, source‐sink dynamics) will be challenging for this system. Although low‐head dams on the UMRS may restrict movements for individuals and populations of certain fish species, we found little evidence that these effects have led to substantial, community‐level fragmentation. Copyright © 2006 John Wiley & Sons, Ltd.     

A Comparison of Metabolic Rates in Off‐Channel Habitats of the Middle Mississippi River

Autochthonous material has been found to be an important base in large river food webs. However, a spatial understanding of primary production in large rivers is lacking. We modeled primary productivity and community respiration (CR) during a low water period in two types of off‐channel habitat present in the Middle Mississippi River, side channels and wing dike fields. Wing dike fields are constantly connected to the main channel and are well mixed along most of their length, while side channels are typically connected only at the top and mouth. Gross primary production (GPP) in wing dike fields ranged from 0.0 to 8.9 g O₂ m^?2 D^?1 and in side channels GPP ranged from 0.4 to 33.5 g O₂ m^?2 D^?1. Both habitat types experienced periods of positive net ecosystem production (NEP) especially in the late summer and early fall. Correlations between metabolic rates and ecosystem characteristics differed between habitat types. Discharge was negatively correlated to NEP in wing dike fields but was not associated with metabolic rates in side channels. Light was positively correlated with GPP and CR at both site types and with NEP in side channels. These areas are protected from high velocity and likely experience greater light penetration, allowing more photosynthesis to take place especially during low water periods. This study demonstrates the potential for high productivity in off‐channel habitats that are permanently connected to the main channel. Copyright © 2016 John Wiley & Sons, Ltd.     

2010—2011年度黄河凌情特点与防凌措施

介绍了2010—2011年度黄河凌汛的基本情况,对内蒙古河段首凌首封日期偏晚、封河发展迅速、开通日期较晚,黄河下游封河长度较长,局部河段出现较大险情的凌情特点以及在凌汛前加大清障力度、建立立体化信息监测系统、凌期科学调度水库拦蓄和分洪工程分水等防凌措施进行了分析,同时对今后的防凌工作提出了建议:①加强宁蒙河段河道测验体系建设,建设水位自动监测和3G汛情视频监视系统;②加强宁蒙河段堤防建设、河道治理,加快内蒙古应急分洪区的建设步伐;③研究针对黄河冰凌特点的破冰技术,列出专项资金解决冰凌观测工器具更新等问题;④向天津、河北供水尽量避开凌情严重的时期,避免增大防凌负担。     

Responses of consumers and food resources to a high magnitude,unpredicted flood in the upper Mississippi River basin

The Mississippi and Missouri Rivers experienced flooding in 1993 that fell outside the annual predictable flood period of spring and early summer. Flooding began in late June, peaked in late July (25 232 m³/s on the upper Mississippi and 21 240 m³/s on the Missouri) and remained at or near flood stage into October 1993. This study was performed to determine if disturbance by an unpredicted flood event would alter trophic dynamics of river–floodplain systems by creating shifts in the composition of organic matter available to consumers. The Ohio River, which did not flood during the same period, was examined for comparison. Stable isotopic ratios of carbon and nitrogen from samples collected in 1993 and 1994 were used to characterize potential food sources and determine linkages between food sources and invertebrate and fish consumers. Pairwise contrasts, performed separately for each river, indicated there were few interannual differences in δ¹³C and δ¹⁵N of organic matter sources and consumers. Between sample period (flood year versus normal water year) trends in both flooded rivers were similar to between‐year trends observed for the Ohio River. Trophic structure of the Mississippi and Ohio Rivers was similar in both years, with fine and ultra‐fine transported organic matter and dissolved organic matter representing the major sources of organic matter. Overlapping isotopic signatures in the Missouri River made tracking of sources through the consumers difficult, but similarities in δ¹³C and δ¹⁵N between years indicated trophic structure did not change in response to the flood. The results suggest that consumers continued to rely on sources of organic matter that would be used in the absence of the unpredicted 1993 flood. It is proposed that trophic structure did not change in response to flooding in the Mississippi and Missouri Rivers because both rivers exhibited the same trends observed in the Ohio River. Copyright © 2001 John Wiley & Sons, Ltd.     

Fish assemblages and biotic integrity of a highly modified floodplain river,the Upper Mississippi,and a large,relatively unimpacted tributary,the Lower Wisconsin

The Upper Mississippi River is a dynamic floodplain river that has been largely transformed by navigational levees and dams since the 1930s. The pools upstream of each dam are lake‐like and only about the upper third of each reach retains a riverine character. In contrast, the Wisconsin River is not managed for commercial navigation and today its lower 149 km represent one of the least‐degraded large river reaches in central North America. Riverine reaches in both the Mississippi and Wisconsin rivers have similar macro‐habitats including numerous islands, large side channels, and connected backwaters and floodplain lakes. In this study, shoreline electrofishing samples were collected during summer 2002 and 2003 to characterize resident fish assemblages. We compared fish species abundance, biomass, and biotic integrity along main and side channel borders between the Upper Mississippi River and the Lower Wisconsin River. We expected that, in the absence of environmental degradation, fish composition and structure would be similar between the Mississippi and Wisconsin rivers, and between channel types within each river. Nonmetric multidimensional scaling and redundancy analysis revealed that fish species in the Mississippi River, unlike in the Wisconsin River, were characteristic of non‐riverine habitats. We consider non‐riverine fish assemblages indicative of environmental impairment. The main and side channel sites in the Mississippi River had more variable fish assemblages than the Wisconsin River. Analyses of fish index of biotic integrity scores showed that environmental condition was excellent for both channel types in the Wisconsin River, whereas in the Mississippi River the side channel was rated good and the main channel only fair. We conclude that differences between the two rivers and between channel types of the Mississippi River are consistent with direct and indirect effects of navigation. This study demonstrates the utility of a fish index of biotic integrity, an inexpensive and rapid bioassessment tool, for detecting change in ecological health on one of the world's largest rivers. Copyright © 2006 John Wiley & Sons, Ltd.     

Natal environments of age‐0 paddlefish in the middle Mississippi River inferred from dentary microchemistry

Effective management and conservation of riverine fish species relies on identification of habitats that contribute recruits to fish populations. Paddlefish are an important commercial and recreational species inhabiting North American large rivers. However, despite the knowledge of adult paddlefish movement patterns in large rivers, their principal natal environments and early life dispersal patterns remain unknown. Paddlefish dentary microchemistry can be used to identify natal environment of fish in large river networks such as the middle Mississippi River (MMR) and tributaries. The goals of this study were to (a) use dentary microchemistry (strontium:calcium ratios; Sr:Ca) to determine natal environment and potential drift for age‐0 paddlefish collected from the MMR and (b) assess whether MMR reach or year of collection influenced the percentage of recruits originating from different rivers. Age‐0 paddlefish were collected during 2010–2011 from two reaches of the MMR (upstream and downstream of the Kaskaskia River confluence). Water samples from the MMR and tributaries (upper Mississippi, Missouri, Illinois, Osage, and Kaskaskia Rivers) were collected during 2006–2016. Water Sr:Ca differed among rivers, enabling identification of natal environment for individual fish using dentary core Sr:Ca. The MMR (44–69% of fish sampled) and Missouri River (25–45% of fish sampled) were the primary natal environments for age‐0 paddlefish across both river reaches and collection years. The upper Mississippi River and smaller tributaries contributed few recruits (<13% of fish sampled). Conservation of paddlefish populations should include maintenance or improvement of connectivity between river reaches used for spawning and juvenile rearing and stock assessments of riverine paddlefish may need to be conducted at a riverscape scale because multiple rivers can contribute to paddlefish recruitment in a particular river reach.     

Process,Policy, and Implementation of Pool‐Wide Drawdowns on the Upper Mississippi River: A Promising Approach for Ecological Restoration of Large Impounded Rivers

The Upper Mississippi River (UMR) has been developed and subsequently managed for commercial navigation by the U.S. Army Corps of Engineers (USACE). The navigation pools created by a series of lock and dams initially provided a complex of aquatic habitats that supported a variety of fish and wildlife. However, biological productivity declined as the pools aged. The River Resources Forum, an advisory body to the St. Paul District of the USACE, established a multiagency Water Level Management Task Force (WLMTF) to evaluate the potential of water level management to improve ecological function and restore the distribution and abundance of fish and wildlife habitat. The WLMTF identified several water level management options and concluded that summer growing season drawdowns at the pool scale offered the greatest potential to provide habitat benefits over a large area. Here we summarize the process followed to plan and implement pool‐wide drawdowns on the UMR, including involvement of stakeholders in decision making, addressing requirements to modify reservoir operating plans, development and evaluation of drawdown alternatives, pool selection, establishment of a monitoring plan, interagency coordination, and a public information campaign. Three pool‐wide drawdowns were implemented within the St. Paul District and deemed successful in providing ecological benefits without adversely affecting commercial navigation and recreational use of the pools. Insights are provided based on more than 17 years of experience in planning and implementing drawdowns on the UMR. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of δD and δ18O as natural markers of invertebrate source environment and dispersal in the middle Mississippi River‐floodplain ecosystem

Movement of invertebrates among large rivers, tributaries, and floodplain lakes or dispersal of adult aquatic insects from riverine or floodplain habitats may provide important subsidies to food webs in receiving habitats. Intensive sampling at habitat interfaces and artificial labelling are two approaches to assess freshwater invertebrate dispersal, but these are difficult to implement at a landscape scale. Natural chemical tracers have been used to track dispersal of fishes and marine invertebrates, but the potential applicability of stable isotope ratios as natural tracers of invertebrate dispersal in freshwater environments has not been assessed. We evaluated stable hydrogen and oxygen isotopes (δD and δ¹⁸O) as natural markers of source environment and dispersal of macroinvertebrates in the middle Mississippi River, tributaries and floodplain wetlands. Water and invertebrates were collected from 12 sites during 2007–2008. Water δD and δ¹⁸O differed among the river, its tributaries, and floodplain wetlands and were strongly correlated with invertebrate δD and δ¹⁸O. Variability in invertebrate δ¹⁸O rendered it ineffective as an indicator of invertebrate source environment. Mean δD of Mississippi River invertebrates differed from δD of invertebrates from floodplain wetlands; δD distinguished invertebrates from these two environments with >80% accuracy. Neither δD nor δ¹⁸O of aquatic insects changed following emergence from their natal site. Preservation method (ethanol or freezing) did not affect invertebrate δD or δ¹⁸O. Invertebrate δD may be a useful natural tracer of natal environment and dispersal in the Mississippi River‐floodplain ecosystem and other freshwater systems where spatial variation in water δD is present. Copyright © 2010 John Wiley & Sons, Ltd.     

2000—2020年黄河下游河岸带生态系统服务价值与碳储分析

为了促进黄河下游生态脆弱河岸带土地资源的合理配置,助力河岸带生态可持续发展,采用野外调查、ArcGIS、InVEST模型、当量因子法等方法,通过分析2000—2020年黄河下游河岸带土地利用动态变化,揭示其生态系统服务总价值（ESV）和碳储量（C_t）的变化。结果表明：2000—2020年黄河下游河岸带湿地和建设用地面积持续增加,湿地主要来源于耕地和水域,建设用地主要来源于耕地;耕地和建设用地面积占比随着距河道距离的增大而增大,而草地面积占比随着距河道距离的增大而减小,林地面积占比随河道距离变化不明显,2000—2010年湿地面积占比随河道距离减少,而2010—2020年远岸湿地增加,且主要位于距河道200~500 m区间。2000—2020年,黄河下游河岸带ESV呈先增加后减少的变化趋势。其中,水域对ESV的贡献率最大,湿地次之,耕地、林地和草地的贡献率低,且不稳定。2000—2020年,黄河下游河岸带碳储量逐渐提高,湿地碳储量逐渐上升,然而林地、草地和水域碳汇能力则先增加后降低。水沙状况、人类活动以及国家政策是影响黄河下游河岸带生态系统服务价值与碳储量的重要因素。为减缓黄河下游人为调水调沙引发的河岸带生态功能减退,亟待提升湿地质量,适当退耕还林、还草和还水,以提高河岸带生态系统的服务价值和碳储量。     

黄河下游河道11月至次年5月时期输沙和冲淤规律研究

利用1960—2010年黄河下游11月至次年5月时期实测水沙资料,系统地研究了黄河下游河道水沙运动和河床冲淤规律。分析了花园口、高村、艾山和利津等4站输沙率与各自上站的流量、含沙量和输沙率的关系,黄河下游河道冲淤量与小浪底站来水量、来沙量、含沙量和来沙系数之间的关系。结果表明:黄河下游河道的下站输沙率与上站输沙率有很好相关关系,该时期进入黄河下游河道的输沙量小于1.82亿t、或平均含沙量小于12.6kg/m3、或来沙系数小于0.014 kg·s/m6时,下游河道以冲刷为主,反之则以淤积为主;采用本文建立的下站输沙率与上站输沙率关系式计算的黄河下游各河段冲淤量具有较高的精度。利用本文建立的关系式可以方便地预测未来黄河下游河道该时期不同河段冲淤量,对快速判断黄河上中游水利工程建设对下游河道冲淤影响具有重要意义。     

Status and Trends in Biotic Integrity in a Sub‐Tropical River Drainage: Analysis of the Fish Assemblage Over a Three Decade Period

We characterized the biotic integrity of the sub‐tropical Duero River, Mexico, comparing current and past index of biotic integrity (IBI) scores with results of an environmental quality index (EQI), inventorying abiotic characteristics and human impacts, and documenting ecosystem changes over the last three decades. We sampled the fish community and measured environmental variables during the dry season of 2009 at 19 sites. We compared 2009 findings with fish data obtained in 1986 and 1991 at nine of the sites. The correlation between the IBI and EQI was high (r² = 0.79, p = 0.0002), indicating that the IBI accurately characterized environmental condition. Thirteen sites were degraded (68%) based on IBI scores, three were fair (16%) and three had good conditions (16%). Based on the EQI, 12 sites were classified as poor (63%), two as fair (11%) and five as good (19%). A cluster analysis of nine abiotic variables and the IBI values yielded three groups: six sites with good integrity and environmental quality, eight with high chemical oxygen demand and four with high total dissolved solids. A discriminant analysis (square canonical correlation: 0.922, and Wilks' lambda significance: 0.001) identified biochemical oxygen demand, distance to vegetation and total dissolved solids as the main predictors. Compared to 1986 and 1991, 2009 IBI values and ratings had declined significantly (multiple response permutation procedure A = 0.16, p = 0.0005), indicating a trend of environmental deterioration, with scores and ratings at 7 of 9 sites lower in 2009. One site had declined from good to fair, one from good to poor, five from fair to poor, one had remained fair and one had remained good. Degradation was related to excessive human water use, reduced river flows, increased wastewater discharge, deforestation, erosion, and invasive species, and mismanagement of preserved sites (springs), all of which highlight an urgent need to reverse declining environmental conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

额尔齐斯河流域1990—2010年湿地遥感监测分析

应用遥感和地理信息系统等技术手段,基于额尔齐斯河流域1990年、2000年、2010年的LandsatTM影像和2005年、2008年的CBERS-02影像,结合多层环境要素数据库、野外定点调查数据等,通过人机交互式解译构建了上述5年额尔齐斯河流域湿地空间数据库。分析了湿地空间数据,总结出额尔齐斯河流域1990—2010年的湿地变化特征。结果表明:天然湿地面积呈波动变化,总体上2010年天然湿地面积大于1990年的面积,增加面积主要来源于湖泊和沼泽及沼泽化草地,而河谷林及滩地的面积呈逐年减小的趋势;人工湿地面积增加较显著,主要因为水浇地面积大幅增加,而水库、坑塘面积呈波动变化,总体上也呈增加趋势。     

Responses of fishes and lampreys to the re‐creation of meanders in a small English chalk stream

River rehabilitation initiatives have become commonplace in European water courses as a result of European Union Water Framework Directive requirements. However, the short‐term responses of fishes to such work have thus far been varied, with some river rehabilitation efforts resulting in demonstrable improvements in diversity and size structure, whereas others have resulted in little or no change. Electrofishing and channel character surveys were conducted annually between 2009 and 2014 on a reach of the River Glaven (North Norfolk, UK) before and after rehabilitation work (embankment removal in 2009 and re‐meandering in 2010) as well as on a control reach immediately upstream. To assess the effects of rehabilitation work, before‐after‐control‐impact analysis tested for changes in channel character (geomorphology, substratum composition, and mesohabitat structure) and in fish species richness, relative abundance, population density, and size structure (calculated after fish data entry into the UK Environment Agency's National Fisheries Population Database). Following re‐meandering work (i.e., treatment), habitat heterogeneity and depth variation increased in the treatment reach, but fish responses were not significant except for biomass and density increases of brown trout Salmo trutta and abundance decreases of European eel Anguilla anguilla, in the treatment but not the control reach. These results are consistent with comparable river rehabilitation initiatives elsewhere, and they suggest that larger‐scale rehabilitations are probably needed to produce greater increases in fish density and diversity. It is recommended that future rehabilitation initiatives address catchment‐scale factors that can enhance ecosystem recovery, for example, removal of barriers to colonization, and increases in connectivity and water quality issues linked to eutrophication, elevated fine sediment inputs, and various pollutants.     

Effects of river discharge on abundance and instantaneous growth of age‐0 carpsuckers in the Oconee River,Georgia, USA

The Oconee River in middle Georgia, U.S.A., has been regulated by the Sinclair Dam since 1953. Since then, the habitat of the lower Oconee River has been altered and the river has become more incised. The altered environmental conditions of the Oconee River may limit the success of various fish populations. Some obligate riverine fishes may be good indicator species for assessing river system integrity because they are intolerant to unfavourable conditions. For example, many sucker species require clean gravel for feeding and reproduction. Further, age‐0 fishes are more vulnerable than adults to flow alterations because of their limited ability to react to such conditions. In this study, we investigated the relationship between abundance and growth of age‐0 carpsuckers to river discharge in the Oconee River. A beach seine was used to collect age‐0 carpsuckers (Carpiodes spp.) from littoral zones of the lower Oconee River from May through July of 1995 to 2001. Regression models were used to assess whether 12 river discharge categories (e.g. peak, low, seasonal flows) influenced age‐0 carpsucker abundance or instantaneous growth. Our analysis indicated that abundance of age‐0 carpsuckers was significantly negatively related to number of days river discharge was >85 m³ s^?1(r² = 0.61, p = 0.04). Estimates of instantaneous growth ranged from 0.10 to 0.90. Instantaneous growth rates were significantly positively related to summer river discharge (r² = 0.95, p <0.01). These results suggest that (1) moderate flows during spawning and rearing are important for producing strong‐year classes of carpsuckers, and (2) river discharge is variable among years, with suitable flows for strong year‐classes of carpsuckers occurring every few years. River management should attempt to regulate river discharge to simulate historic flows typical for the region when possible. Such an approach is best achieved when regional climatic conditions are considered. Published in 2007 by John Wiley & Sons, Ltd.