An Assessment of Fish Assemblage Structure in a Large River

The Penobscot River drains the largest watershed in Maine and once provided spawning and rearing habitats to 11 species of diadromous fishes. The construction of dams blocked migrations of these fishes and likely changed the structure and function of fish assemblages throughout the river. The proposed removal of two main‐stem dams, improved upstream fish passage at a third dam, and construction of a fish bypass on a dam obstructing a major tributary is anticipated to increase passage of and improve habitat connectivity for both diadromous and resident fishes. We captured 61 837 fish of 35 species in the Penobscot River and major tributaries, through 114 km of boat electrofishing. Patterns of fish assemblage structure did not change considerably during our sampling; relatively few species contributed to seasonal and annual variability within the main‐stem river, including smallmouth bass Micropterus dolomieu, white sucker Catostomus commersonii, pumpkinseed Lepomis gibbosus, and golden shiner Notemigonus crysoleucas. However, distinct fish assemblages were present among river sections bounded by dams. Many diadromous species were restricted to tidal waters downriver of the Veazie Dam; Fundulus species were also abundant within the tidal river section. Smallmouth bass and pumpkinseed were most prevalent within the Veazie Dam impoundment and the free‐flowing river section immediately upriver, suggesting the importance of both types of habitat that supports multiple life stages of these species. Further upriver, brown bullhead Ameiurus nebulosus, yellow perch Perca flavescens, chain pickerel Esox niger, and cyprinid species were more prevalent than within any other river section. Our findings describe baseline spatial patterns of fish assemblages in the Penobscot River in relation to dams with which to compare assessments after dam removal occurs. Copyright © 2014 John Wiley & Sons, Ltd.     

Anthropogenic Disturbance and Environmental Associations with Fish Assemblage Structure in Two Nonwadeable Rivers

Nonwadeable rivers are unique ecosystems that support high levels of aquatic biodiversity, yet they have been greatly altered by human activities. Although riverine fish assemblages have been studied in the past, we still have an incomplete understanding of how fish assemblages respond to both natural and anthropogenic influences in large rivers. The purpose of this study was to evaluate associations between fish assemblage structure and reach‐scale habitat, dam, and watershed land use characteristics. In the summers of 2011 and 2012, comprehensive fish and environmental data were collected from 33 reaches in the Iowa and Cedar rivers of eastern‐central Iowa. Canonical correspondence analysis (CCA) was used to evaluate environmental relationships with species relative abundance, functional trait abundance (e.g. catch rate of tolerant species), and functional trait composition (e.g. percentage of tolerant species). On the basis of partial CCAs, reach‐scale habitat, dam characteristics, and watershed land use features explained 25.0–81.1%, 6.2–25.1%, and 5.8–47.2% of fish assemblage variation, respectively. Although reach‐scale, dam, and land use factors contributed to overall assemblage structure, the majority of fish assemblage variation was constrained by reach‐scale habitat factors. Specifically, mean annual discharge was consistently selected in nine of the 11 CCA models and accounted for the majority of explained fish assemblage variance by reach‐scale habitat. This study provides important insight on the influence of anthropogenic disturbances across multiple spatial scales on fish assemblages in large river systems. Copyright © 2014 John Wiley & Sons, Ltd.     

A Community‐Level,Mesoscale Analysis of Fish Assemblage Structure in Shoreline Habitats of a Large River Using Multivariate Regression Trees

The mesoscale (10⁰–10² m) of river habitats has been identified as the scale that simultaneously offers insights into ecological structure and falls within the practical bounds of river management. Mesoscale habitat (mesohabitat) classifications for relatively large rivers, however, are underdeveloped compared with those produced for smaller streams. Approaches to habitat modelling have traditionally focused on individual species or proceeded on a species‐by‐species basis. This is particularly problematic in larger rivers where the effects of biological interactions are more complex and intense. Community‐level approaches can rapidly model many species simultaneously, thereby integrating the effects of biological interactions while providing information on the relative importance of environmental variables in structuring the community. One such community‐level approach, multivariate regression trees, was applied in order to determine the relative influences of abiotic factors on fish assemblages within shoreline mesohabitats of San Pedro River, Chile, and to define reference communities prior to the planned construction of a hydroelectric power plant. Flow depth, bank materials and the availability of riparian and instream cover, including woody debris, were the main variables driving differences between the assemblages. Species strongly indicative of distinctive mesohabitat types included the endemic Galaxias platei. Among other outcomes, the results provide information on the impact of non‐native salmonids on river‐dwelling Galaxias platei, suggesting a degree of habitat segregation between these taxa based on flow depth. The results support the use of the mesohabitat concept in large, relatively pristine river systems, and they represent a basis for assessing the impact of any future hydroelectric power plant construction and operation. By combing community classifications with simple sets of environmental rules, the multivariate regression trees produced can be used to predict the community structure of any mesohabitat along the reach. Copyright © 2015 John Wiley & Sons, Ltd.     

Historical Changes in Fish Assemblage Composition Following Water Quality Improvement in the Mainstem Trinity River of Texas

The Clean Water Act of 1972 is credited with improving water quality across the USA, although few long‐term studies tracking hydrologic, chemical, and biological responses to cleanup efforts exist. The Trinity River of Texas was plagued by poor water quality for more than a century before passage of legislation to reduce point source pollution from the Dallas–Fort Worth (DFW) Metroplex. We tracked changes in components of flow regime; concentrations of ammonia, nitrate, phosphorus, and biochemical oxygen demand (BOD); and fish assemblage composition in three mainstem reaches during a 40‐year period (1968–2008) following implementation of a large‐scale cleanup initiative. Results suggest little change in flow regime components such as magnitude, timing, and rate of change among the three reaches during 1968–2008. Concentrations of water quality parameters declined through time and with greater distance from DFW, including the lowest concentrations in the reach downstream of a mainstem reservoir (Lake Livingston). Fish assemblage composition shifts correlated with attenuated nutrient and BOD concentrations, and species richness generally increased among all reaches. Native and intolerant fishes consistently increased through time among all three reaches, although lentic and non‐native species also increased downstream of Lake Livingston. Our findings suggest a revitalization of the Trinity River fish assemblage associated with reduced nutrient pollution in DFW (even among distant reaches) and also illustrate potential confounding factors such as stream impoundment and continued nutrient deposition that likely preclude complete recovery. Copyright © 2014 John Wiley & Sons, Ltd.     

Low‐Head Dam Impacts on Habitat and the Functional Composition of Fish Communities

The natural flow regime of many rivers in the USA has been impacted by anthropogenic structures. This loss of connectivity plays a role in shaping river ecosystems by altering physical habitat characteristics and shaping fish assemblages. Although the impacts of large dams on river systems are well documented, studies on the effects of low‐head dams using a functional guild approach have been fewer. We assessed river habitat quality and fish community structure at 12 sites on two rivers; the study sites included two sites below each dam, two sites in the pool above each dam and two sites upstream of the pool extent. Fish communities were sampled from 2012 to 2015 using a multi‐gear approach in spring and fall seasons. We aggregated fishes into habitat and reproductive guilds in order to ascertain dams' effects on groups of fishes that respond similarly to environmental variation. We found that habitat quality was significantly poorer in the artificial pools created above the dams than all other sampling sites. Fast riffle specialist taxa were most abundant in high‐quality riffle habitats farthest from the dams, while fast generalists and pelagophils were largely restricted to areas below the downstream‐most impoundment. Overall, these dams play a substantial role in shaping habitat, which impacts fish community composition on a functional level. Utilizing this functional approach enables us to mechanistically link the effects of impoundments to the structure of fish communities and form generalizations that can be applied to other systems. Copyright © 2017 John Wiley & Sons, Ltd.     

我国鱼类洄游通道和生境恢复技术研究现状分析

我国目前处于水电开发建设的高峰时期,生态环境保护问题受到高度重视。人们对河流资源的开发利用阻隔了鱼类自由迁徙的洄游通道,大大影响了鱼类赖以生存的环境,亟需发展洄游通道和鱼类生境的恢复技术来加以保护。阐述了鱼类洄游通道和生境恢复的重要意义,总结了该类技术在我国的研究现状和发展过程,指出了我国鱼类洄游通道技术发展面临的主要问题和挑战。通过对21世纪以来(特别是最近5 a)国家自然科学基金资助的相关项目及研究成果分析,指明了目前我国鱼类洄游通道和生境恢复技术的主要努力方向,包括:①各种典型鱼类的生活习性和游泳行为能力;②鱼类种群分布及生境因子影响规律;③水电开发对鱼类生境因子的影响规律;④洄游通道和生存环境恢复措施及过鱼效果验证。     

Habitat diversity and fish assemblage structure in local river widenings: A case study on a swiss river

We investigated habitat availability and fish assemblage structure in three local river widenings, completed 3–14 years ago, and five adjacent canalized reaches on the river Thur, a seventh‐order river in Switzerland. To account for seasonal variability, surveys were repeated in winter and summer 2005. Results were compared with historical pre‐disturbance data to evaluate whether the current abiotic and biotic conditions in the study reaches have attained historic near‐natural levels. Hydro‐physical habitat diversity (depth, flow velocity, cover availability) was considerably greater in the two longer widenings (>900 m length) than in the canalized reaches and in the shortest widening (300 m length), with higher proportions of shallow or deep areas of different flow velocities. However, the comparison of current and historical near‐natural shoreline lengths indicated that the current geomorphological complexity is still considerably impaired in all reaches. No overall significant relationship was found between the reach type (canalized or rehabilitated) and the number of species or the total fish abundance which were strongly correlated with the availability of suitable cover and moderate flow velocity. However, highest winter abundances were observed in deep, well‐structured backwaters of the rehabilitated reaches, documenting their significance as wintering habitats. Assemblage structure and composition were similar in canalized and rehabilitated reaches. Compared to the historical data, however, fewer and different dominant species were found, and guild composition changed towards a higher representation of generalists and tolerant species. Copyright © 2008 John Wiley & Sons, Ltd.     

Fish and Benthic Macroinvertebrate Assemblage Response to Removal of a Partially Breached Lowhead Dam

Dam removal is an increasingly common restoration technique in lotic ecosystems. Potential dam removal benefits include improved aquatic organism passage, restoration of natural flow dynamics and a general improvement in habitat for native species. However, understanding potential dam removal outcomes requires data on ecosystem response in a wide variety of settings. We evaluated fish and benthic macroinvertebrate response to removal of the Spruce Pine dam in western North Carolina, USA. This dam was partially breached prior to removal, and impounded a coolwater river, both scenarios under which dam removal has been under‐studied. Post‐removal shifts in fish and benthic macroinvertebrate assemblages did not occur, suggesting that previously documented patterns of assemblage change in response to dam removal, particularly in the area upstream from the dam, are not universal, and may depend upon factors such as river gradient and water temperature, and the available species pool. Such information can aid managers in identifying conditions under which an expectation of significant instream habitat improvement in response to dam removal may not be warranted. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Differences among Expert Judgments of Fish Habitat Suitability and Implications for River Management

Expert judgment is regularly used in ecology for assessing the suitability of habitats, in particular of rare or endangered species or species with limited empirical data. Yet, differences in expert judgment of habitat suitability and consequent implications for ecosystem management have not been evaluated and are largely ignored. Here, we evaluated the variability of 13 expert judgments and the related uncertainty in hydraulic habitat suitability modelling using the riverine fish species Phoxinus phoxinus as a model species. We found (i) the highest agreement among experts identifying the best and fully unsuited habitat conditions, but (ii) that disagreement among experts is surprisingly large, (iii) with largest differences related to the experts' perception of flow velocity and (iv) that semi‐suitable transition areas between high and low habitat suitability are most susceptible to disagreements. We emphasize that expert judgment of habitat suitability is useful for many applications and especially highly suitable habitats would be reliably identified by experts. However, expert judgment‐based assessments should be iterative processes that include both different experts and feedback on the potential effects of their assessments. Furthermore, we recommend that expert judgment should not replace data‐driven empirical ecology but its benefits can rather complement it. Copyright © 2016 John Wiley & Sons, Ltd.     

二维水流数学模型在多分汊河道鱼类栖息地设计中的应用

多分汊河道汇合或分流口水流流态复杂,常常存在河口滩及深槽,复杂多样的水文水力条件为鱼类提供了良好的进食及休憩场所。针对多分汊河道边界复杂的特点,建立了基于一般曲线坐标系下的平面二维水流数学模型。将所建立的数学模型应用于大渡河乐山段安谷水电站左岸生态河网建设和鱼类栖息地设计,对工程投运前后河段的水深、流速、流场、分流比进行模拟和对比分析,设置生态工程措施,使得鱼类产卵场河段水流特性仍满足鱼类栖息地要求。从安谷水电站运行效果看,设计的生态措施对河道鱼类栖息改善取得了较好的实践效果。     

Fish assemblage response to recent mitigation of a channelized warmwater stream

Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd.     

Quantifying Fish Habitat Associated with Stream Simulation Design Culverts in Northern Wisconsin

This study investigated the effects of culvert replacement design on fish habitat and fish weight by comparing substrate diversity and weight at three stream simulation (SS)‐design and three bankfull and backwater (BB)‐design sites on the Chequamegon‐Nicolet National Forest, Wisconsin. Stream channel cross‐sections, Wolman substrate particle counts, and single‐pass backpack electro‐fishing survey data were used to quantify fish habitat and fish weight in 50‐m upstream and downstream sample reaches at each site. We applied generalized linear mixed models to test the hypothesis that substrate size and fish weight did not differ according to stream‐crossing design type (SS or BB) and location (upstream or downstream). Substrate particle sizes were significantly greater upstream of the stream crossing when compared to downstream of the stream crossing at both SS and BB sites for riffles and pools. Substrate particle sizes were also significantly greater upstream of BB sites when compared to upstream of SS sites. Results of this study indicated statistically greater individual fish weights upstream of SS‐design sites in comparison to upstream of BB‐design sites in first‐ to third‐order low gradient streams. These results suggested that the SS‐design approach appears to be more effective at transporting sediment downstream, and illustrated the value of using fish weight as an indicator of biological success for stream‐crossing designs. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.     

Structure of endemic fish assemblages in the upper Yangtze River Basin

This study focused on characterizing the endemic fish assemblages in the upper Yangtze River Basin and identifying the relative influences of catchment land‐cover variables on observed fish patterns in order to suggest a conservation strategy. A model based on a self‐organizing map was applied to determine endemic fish assemblages along the river network, based on presence/absence data for 124 endemic species. Five fish assemblages (Ia, Ib, IIa, IIb1, IIb2) were described. These assemblages varied significantly in terms of individual species patterns as well as species richness. Indicator species were identified for each class of community (0, 3, 9, 27, 0 species for cluster Ia, Ib, IIa, IIb1, IIb2, respectively). Structure of the endemic fish assemblages in the upper Yangtze River was highly correlated with local topographic and geomorphic characteristics. Simultaneously, the catchment land cover features also reflected out this endemic fish distribution structure. Among 18 land‐cover types, alpine and sub‐alpine meadow, together with farmland, were revealed to be the most important factors both in discriminating the endemic fish assemblages and in correlating species distributions by using discriminant analysis and co‐inertia analysis. Finally, in order to preserve the rare and endemic fish in the upper Yangtze River, reserve networks, rather than a single national nature reserve, should be established. Copyright © 2009 John Wiley & Sons, Ltd.     

Diversity and Community Structure of Fishes in the Regulated Versus Unregulated Tributaries of the Mekong River

Diversity and community structure of fishes were studied in three neighbouring tributaries of the Mekong River in Thailand, namely the Mun, Songkhram and Gam Rivers. The rivers are located in the same ecoregion but have contrasting levels of both hydrological regulations and mitigation measures; the Mun River has a hydropower dam with a fish ladder and sluice gates that are opened during the wet season each year, the Gam River has several irrigation dams with a fish ladder at each dam site, and the Songkhram River has no dams along its river course. A total of 124 freshwater fish species were sampled in these rivers from August 2009 to June 2010. Overall species richness was highest in the Songkhram River (112), followed by the Mun (97) and Gam (54) Rivers. Average per site species richness was also significantly different among rivers but not among sampling months. Abundance–biomass comparison plots revealed considerably overlapping distributions of these two metrics from the dry to early rainy seasons in the Songkhram River and, to a lesser extent, in the Mun River. Fish assemblage data were classified into six clusters with similar community structure. Fish assemblages in the Gam River constituted a single cluster, while those in the other two rivers formed multiple clusters depending on the sampling season. The results of the cluster analysis are discussed in relation to the dominance of the three migration guilds (white, black, and grey fishes) of the Mekong River fishes. The effectiveness of the mitigation measures was determined to be limited in alleviating adverse impacts of dams in these tributaries of the Mekong River. Copyright © 2014 John Wiley & Sons, Ltd.     

1998-2001年长江口近海鱼类群聚结构及其与环境因子的关系

根据1998-2001年长江口近海4个航次鱼类拖网调查数据,运用群落生态学分类和排序方法,分析了长江口近海鱼类群聚结构特征及其与环境因子的关系。筛选后的64个站次的48种长江口近海鱼类分属10目28科,鲈形目种类最多,灯笼鱼目,鲈形目和鲱形目鱼类丰度共占总丰度的 99.81% 。龙头鱼、七星底灯鱼和黄鲫为秋季优势种,银鲳和皮氏叫姑鱼为春季优势种。相同季节年度间的鱼类群聚差异不显著,春季(5月)和秋季(11月)鱼类群聚有明显的季节分化。CCA分析显示：1998-2001年长江口近海鱼类群聚的主要影响因素是水深、底层温度、底层溶解氧、表层总磷和pH值。     

仿自然通道及鱼道池室结构布置研究

为了提高仿自然通道及鱼道设计水平,以某水电站仿自然通道工程为案例,根据其过鱼需求,提出了池室结构布置方案,并通过数值模拟及物理模型试验对其平面及三维池室流态进行了分析。结果表明:通过在仿自然通道或鱼道内部采用收缩段、侧壁设置消能墩、底部辅以条形消能墩的新型结构可使池室内部流场实现纵向分层和横向分区,可供不同游泳能力的鱼类通过。该池室结构在流速流态控制等方面较普通仿自然通道和技术型鱼道均具有优势,适合多种鱼类通过,具有推广价值。     

A Comparison of Main and Side Channel Physical and Water Quality Metrics and Habitat Complexity in the Middle Mississippi River

Worldwide large rivers have been severely modified by human intervention. Many modifications result in disconnection of the river from floodplain and off‐channel habitats generally characterized by lower velocities and Copyright © 2016 John Wiley & Sons, Ltd. shallower depths relative to the main channel, conditions vital to many organisms. Extensive levees on the Middle Mississippi River (MMR) have cut off backwater systems and disconnected the river from 80% of its floodplain. However, the system is characterized by large side channels associated with islands. We examined a long term data set for differences in physical (e.g. depth and velocity) and water quality metrics (e.g. temperature, suspended solids, dissolved oxygen, chlorophyll, % organic matter) between the main and side channels of a 128‐km reach of the MMR. We compared variability between main and side channels using the coefficient of variation (COV). All metrics differed between habitats. Side channels were shallower with lower velocities and had greater mean and COV of % organic matter and more variable dissolved oxygen concentrations. Velocity, temperature, and suspended solids were similar in the spring. COVs were lowest in both habitats during the spring for all metrics except temperature and DO. Resource management in the MMR tends to focus on maintaining existing side channels because of the difficulty of working in the heavily used navigation channel. This study shows that these actions protect areas that function differently than the main channel for most of the year. However, our results also highlight the need for restoration activities aimed at restoring floodplain connectivity, especially during the spring. Copyright © 2016 John Wiley & Sons, Ltd.     

Patchiness in a Large Floodplain River: Associations Among Hydrology,Nutrients, and Fish Communities

Large floodplain rivers have internal structures shaped by directions and rates of water movement. In a previous study, we showed that spatial variation in local current velocities and degrees of hydrological exchange creates a patch‐work mosaic of nitrogen and phosphorus concentrations and ratios in the Upper Mississippi River. Here, we used long‐term fish and limnological data sets to test the hypothesis that fish communities differ between the previously identified patches defined by high or low nitrogen to phosphorus ratios (TN:TP) and to determine the extent to which select limnological covariates might explain those differences. Species considered as habitat generalists were common in both patch types but were at least 2 times as abundant in low TN:TP patches. Dominance by these species resulted in lower diversity in low TN:TP patches, whereas an increased relative abundance of a number of rheophilic (flow‐dependent) species resulted in higher diversity and a more even species distribution in high TN:TP patches. Of the limnological variables considered, the strongest predictor of fish species assemblage and diversity was water flow velocity, indicating that spatial patterns in water‐mediated connectivity may act as the main driver of both local nutrient concentrations and fish community composition in these reaches. The coupling among hydrology, biogeochemistry, and biodiversity in these river reaches suggests that landscape‐scale restoration projects that manipulate hydrogeomorphic patterns may also modify the spatial mosaic of nutrients and fish communities. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.