DISTRIBUTION AND ABUNDANCE OF STREAM FISHES IN RELATION TO BARRIERS: IMPLICATIONS FOR MONITORING STREAM RECOVERY AFTER BARRIER REMOVAL

Dams are ubiquitous in coastal regions and have altered stream habitats and the distribution and abundance of stream fishes in those habitats by disrupting hydrology, temperature regime and habitat connectivity. Dam removal is a common restoration tool, but often the response of the fish assemblage is not monitored rigorously. Sedgeunkedunk Stream, a small tributary to the Penobscot River (Maine, USA), has been the focus of a restoration effort that includes the removal of two low‐head dams. In this study, we quantified fish assemblage metrics along a longitudinal gradient in Sedgeunkedunk Stream and also in a nearby reference stream. By establishing pre‐removal baseline conditions and associated variability and the conditions and variability immediately following removal, we can characterize future changes in the system associated with dam removal. Over 2 years prior to dam removal, species richness and abundance in Sedgeunkedunk Stream were highest downstream of the lowest dam, lowest immediately upstream of that dam and intermediate farther upstream; patterns were similar in the reference stream. Although seasonal and annual variation in metrics within each site was substantial, the overall upstream‐to‐downstream pattern along the stream gradient was remarkably consistent prior to dam removal. Immediately after dam removal, we saw significant decreases in richness and abundance downstream of the former dam site and a corresponding increase in fish abundance upstream of the former dam site. No such changes occurred in reference sites. Our results show that by quantifying baseline conditions in a small stream before restoration, the effects of stream restoration efforts on fish assemblages can be monitored successfully. These data set the stage for the long‐term assessment of Sedgeunkedunk Stream and provide a simple methodology for assessment in other restoration projects. Copyright © 2011 John Wiley & Sons, Ltd.     

Habitat Restoration in the Context of Watershed Prioritization: The Ecological Performance of Urban Stream Restoration Projects in Portland,Oregon

In Portland (Oregon, USA), restoration actions have been undertaken at the watershed scale (e.g. revegetation and stormwater management) to improve water quality and, where water quality and quantity are adequate at the reach scale, to increase habitat heterogeneity. Habitat enhancement in urban streams can be important for threatened species, but challenging, because of altered catchment hydrology and urban encroachment on floodplains and channel banks. To evaluate reach‐scale restoration projects in the Tryon Creek watershed, we sampled benthic macroinvertebrates and conducted habitat quality surveys pre‐project and over 4 years post‐project. Species sensitive to pollution and diversity of trophic groups increased after restoration. Taxonomic diversity increased after restoration but was still low compared with reference streams. We found no significant changes in trait proportions and functional diversity. Functional diversity, proportion of shredders and semivoltine invertebrates were significantly higher in reference streams than in the restored stream reaches. We hypothesized that inputs of coarse particulate organic matter and land use at watershed scale may explain the differences in biodiversity between restored and reference stream reaches. Habitat variables did not change from pre‐project to post‐project, so they could not explain community changes. This may have been partly attributable to insensitivity of the visual estimate methods used but likely also reflects the importance of watershed variables on aquatic biota—suggesting watershed actions may be more effective for the ecological recovery of streams. For future projects, we recommend multihabitat benthic sampling supported by studies of channel geomorphology to better understand stream response to restoration actions. Copyright © 2014 John Wiley & Sons, Ltd.     

Aquatic vegetation responses to island construction (habitat restoration) in a large floodplain river

The Upper Mississippi River is maintained in its current navigable state through impoundments, dredging, and other engineering projects. These stressors, along with anthropogenic impacts and natural system processes, led to declines in aquatic vegetation and the loss of fish and wildlife habitat, with a major downturn the late 1980s and early 1990s. Large‐scale restoration projects, such as the one evaluated here, are primarily designed to rehabilitate and enhance fish and wildlife habitat. We determined whether an individual restoration project, construction of an island complex, fulfilled a programmatic goal of re‐establishing diverse and abundant native aquatic vegetation. Eighteen years of aquatic vegetation monitoring data from impact and reference areas were compared to evaluate the anticipated direct effects (within 400 m of the constructed islands) and indirect effects (>400 m downstream of constructed islands) of restoration. Impact areas were also compared with an unrestored negative reference area ~200 km downstream of the project and with a positive reference area in adjacent, relatively natural backwaters. Only indirect effects of restoration were evident. Prevalence and species richness of aquatic vegetation in both of the impact areas and in the negative reference area increased prior to restoration, suggesting large‐scale improvement independent of the project examined here. Indirect effects were demonstrated as further increases in both prevalence and species richness coinciding with restoration in the area >400 m downstream of the restoration. We conclude that increased abundance and diversity of aquatic vegetation was partially achieved, with observed improvements potentially linked to reduced wind fetch.     

Population effect of a large‐scale stream restoration effort on Chinook salmon in the Pahsimeroi River,Idaho

Stream habitat restoration is an important tool for fisheries management in impaired lotic systems. Although small‐scale benefits of stream habitat restoration are commonly investigated, it is difficult to demonstrate population effects. The Pahsimeroi River Chinook salmon Oncorhynchus tshawytscha population was previously restricted to the lower portion of the river by multiple irrigation structures. To address fish passage issues, a combination of restoration projects was initiated including barrier removals, instream flow enhancements and installation of fish screens on diversions. The largest barrier was removed in 2009, more than doubling the amount of accessible linear habitat. We hypothesized restoration efforts would expand the distribution of spawning salmon in the Pahsimeroi River watershed, leading to a broader distribution of juveniles. We also hypothesized a broader juvenile distribution would have population effects by reducing the prevalence of density‐dependent growth and survival. Redds were documented in newly accessible habitat immediately following barrier removal and accounted for a median of 42% of all redds in the Pahsimeroi River watershed during 2009–2015. Snorkel surveys also documented juvenile rearing in newly accessible habitat. Juvenile productivity increased from a median of 64 smolts/female spawner for brood years 2002–2008 to 99 smolts/female spawner for brood years 2009–2014. Overall, results suggested increased habitat accessibility in the Pahsimeroi River broadened the distribution of spawning adult and rearing juvenile salmon and reduced the effects of density‐dependent survival. Large‐scale stream restoration efforts can have a population effect. Despite the large‐scale effort and response, habitat restoration alone is likely not sufficient to restore this population.     

EFFECTS OF BENTHIC HABITAT RESTORATION ON NUTRIENT UPTAKE AND ECOSYSTEM METABOLISM IN THREE HEADWATER STREAMS

The assemblage of stream habitat types can drive biofilm composition and activity in headwater streams, thereby influencing rates of ecosystem function. However, the influence of human‐induced alterations to the distribution of benthic habitat such as construction, land‐use changes and restoration on biofilm‐mediated processes has not been well studied. We measured nutrient uptake of ammonium, nitrate and phosphate, as well as gross primary production and community respiration in three streams in Michigan, USA, each with an upstream reference and a downstream restored reach. The restoration included a 10‐m sediment trap, paired with 40–60 m of gravel and boulder added downstream and designed to retain sediment, stabilize banks and provide spawning habitat for trout. We sampled four times in the six stream reaches from May 2006 to September 2007. Across streams, restored reaches reflected the structural manipulation with increased predominance of coarse inorganic sediments, higher gas exchange rate and increased transient storage. However, nutrient uptake and community respiration rates were different between reaches at only one site. The ecosystem response by this stream was driven by the large differences in coarse inorganic habitat between reference and restored reaches. We conclude that restorations of benthic habitat which are visually conspicuous, such as creation of settling pools and gravel‐filled reaches, did not universally affect stream ecosystem function. Initial conditions and magnitude of change may be key factors to consider in explaining functional responses, and predicting the influence of habitat restoration on ecosystem function remains a challenge. Copyright © 2011 John Wiley & Sons, Ltd.     

BENCHMARKING RIVER HABITAT IMPROVEMENT

River ecosystems have witnessed a long history of human pressure, particularly the disruption of freshwater fish populations. The awareness of this situation has led to many habitat improvement projects, with a variable degree of success. In natural situations, fish populations co‐inhabit throughout the hydrological cycle with different degrees of adequacy, and the sequence of favourable and unfavourable conditions dictates abiotic constraints and biotic interactions that shape the final biological assemblages. We postulate that a part of unsuccessful restoration results is related to insufficient closeness to the natural habitat conditions of the river type that is to be restored, including the naturally adverse periods. We used the river2d model to predict habitat availability as weighted usable area (WUA) at a degraded site that is to be restored, for two native Mediterranean species and their life stages—the Southwestern nase Iberochondrostoma almacai and the Arade chub Squalius aradensis. We then analysed the yearly evolution of the natural WUA at a nearby reference site. Overall, the reference site exhibited the longest periods during which the WUA was continuously lower than the chosen WUA thresholds for each of the four bioperiods. Considerable divergences from natural habitat availability values can be seen for the spawning, rearing and growth bioperiods. Restoration outcomes can result in appreciable deviations—favourable or unfavourable to fish populations—from the WUA occurring under natural conditions over the course of the year. Restoration should therefore take account of local hydraulic and habitat patterns that govern population dynamics and result in the final fish assemblage. Copyright © 2011 John Wiley & Sons, Ltd.     

Scenarios for Restoring Floodplain Ecology Given Changes to River Flows Under Climate Change: Case from the San Joaquin River,California

Freshwater ecosystem health has been increasingly linked to floodplain connectivity, and some river restoration efforts now overtly target reconnecting floodplain habitats for species recovery. The dynamic nature of floodplain habitats is not typically accounted for in efforts to plan and evaluate potential floodplain reconnection projects. This study describes a novel approach for integrating streamflow dynamics with floodplain area to quantify species‐specific habitat availability using hydraulic modelling, spatial analysis and statistical measures of flow regime. We used this hydro‐ecological modelling approach to examine the potential habitat for splittail (Pogonichthys macrolepidotus), Chinook salmon (Oncorhynchus tshawytscha) and their food resources under two restoration treatments and two climate change flow scenarios for a study site on San Joaquin River in California. Even with the addition of new floodplain through restoration efforts, the modelling results reveal only 13 streamflow events in the past 80 years had the magnitude and duration required for splittail spawning and rearing, and 14 events had flows long enough for salmon rearing benefits. Under climate change, modelled results suggest only 4–17% of the years in the rest of this century are likely to produce required flow‐related habitat conditions for splittail and salmon rearing along the study reach. Lastly, we demonstrate by simulating augmented reservoir releases that restoration of fish habitat will require a more natural flow regime to make use of restored floodplain and achieve the desired hydrologic habitat connectivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Fish community response to habitat variables in two restored side channels of the lower Platte River,Nebraska

Anthropogenic alterations to large rivers ranging from impoundments to channelization and levees have caused many rivers to no longer access the floodplain in a meaningful capacity. Floodplain habitats are important to many riverine fishes to complete their life‐history strategies. The fish community and species of fish that inhabit floodplain habitats are often dictated by the type of habitat and the conditions within that habitat (e.g., temperature, water velocity, depth, and discharge). As mitigation and restoration projects are undertaken, it is imperative that managers understand how various habitat components will affect the fish community in floodplain habitats. We collected fish and habitat data from two restored side channels with different structural designs on the lower Platte River, Nebraska, to determine how habitat variables predicted species diversity and individual species presence. We found a decrease in discharge in the main‐stem river resulted in increased diversity in one of the side channels, with the greatest diversity values occurring during summer. No habitat variables performed well for predicting fish species diversity for an adjacent side channel with more uniform depth and velocity and no groundwater inputs. However, several native riverine fish species in this side channel were shown to be associated with high temperature, dissolved oxygen, main‐stem discharge, and discharge variability. These results highlight the importance of considering the physical design of restored floodplain habitats when attempting to enhance fish communities.     

A Synthesis of Stream Restoration Efforts in Florida (USA)

Studies summarizing stream restoration projects in the US are outdated and omit the majority of restoration projects in Florida. To address this gap, we compiled stream restoration data from diverse sources to create a Florida Stream Restoration Database (FSRD, available at http://www.watershedecology.org/databases.html ) containing information on project type, location, completion date, and costs. The FSRD contains 178 projects categorized by restoration type, including riparian management (23%), stream reclamation (19%), flow modification (13%), bank stabilization (12%), channel reconfiguration (11%), in‐stream habitat improvements (11%), floodplain reconnection (6%), invasive species removal (4%), and dam removal (1%). Projects were spatially clustered into three geographic regions, providing insight on the diversity of initiatives, needs, and funding sources of land management agencies and private landowners that motivated restoration efforts. Projects in the Florida panhandle emphasized in‐stream habitat restoration, while peninsular projects were dominated by flow modification, and projects in the west central region focused on stream reclamation to mitigate surface mining practices and water quality and habitat improvements in tidal streams. Results suggest that Florida is spending much more on stream restoration than previously documented. Between 1979 and 2015, the mean and median stream restoration project costs in Florida were $15.4 million and $180 000, respectively, indicating a strongly skewed distribution because of the large Kissimmee River restoration project in central Florida. This work highlights the need for, and utility of, statewide and national restoration databases to improve restoration tracking. This need will become increasingly critical as more stringent water quality and habitat mitigation rules are implemented across the country. Copyright © 2016 John Wiley & Sons, Ltd.     

Monitoring the channel process of a stream restoration project in an urbanizing watershed: a case study of Kelley Creek,Oregon, USA

Pacific Northwest (PNW) streams in the United States were impacted by the 20th century development, when removal of instream structure and channelization degraded an aquatic habitat. The lower Kelley Creek in southeast Portland, USA was channelized during the 1930's Works Progress Administration (WPA) projects. Stream restoration reintroduced pool‐riffle sequences and heterogeneous substrates to protect salmonids while mitigating impacts from flooding. We investigated whether the restored pool‐riffle morphology changed substantially following effective discharge events. We examined channel forms for four reaches representing three time periods—pre‐development (two reference reaches), development and restoration. We conducted thalweg profiles, cross‐sections and pebble counts along the reaches to examine how channel geometry, residual pool dimensions and particle size distribution changed following effective discharge events. The effective discharge flows altered the restoration reach more substantially than the reference reaches. The restoration reach decreased in median particle size, and its cross‐sectional geometry aggraded near its margins. However, the residual pool morphology remained in equilibrium. Richardson Creek's reference reach degraded at the substrate level, while Kelley Creek's reference reach remained in equilibrium. The restoration reach's aggradation may have resulted from sedimentation along the nearby Johnson Creek. In contrast, Richardson Creek's degradation occurred as upstream land use may have augmented flows. Stream channels with low gradient pool‐riffle morphologies are ideal for salmonid spawning and rearing and should be protected and restored within urban corridors. The findings of our study suggest that the connectivity of streams and the dynamic fluvial geomorphology of stream channels should be considered for stream restoration projects in humid temperate climates. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of Road Crossings on Habitat Connectivity for Stream‐Resident Fish

Road crossings can act as barriers to the movement of stream fishes, resulting in habitat fragmentation, reduced population resilience to environmental disturbance and higher risks of extinction. Strategic barrier removal has the potential to improve connectivity in stream networks, but managers lack a consistent framework for determining which projects will most benefit target species. The objective of this study is to develop a method for identifying and prioritizing action on road crossings in order to restore stream network connectivity. We demonstrate the method using a case study from the Pine‐Popple watershed in Wisconsin. First, we propose a new metric for quantifying stream connectivity status for stream‐resident fish. The metric quantifies the individual and cumulative effects of barriers on reach and watershed level connectivity, while accounting for natural barriers, distance‐based dispersal limitations and variation in habitat type and quality. We conducted a comprehensive field survey of road crossings in the watershed to identify barriers and estimate replacement costs. Of the 190 surveyed road crossings, 74% were determined to be barriers to the movement of at least one species or life stage of fish, primarily due to high water velocity, low water depth or outlet drops. The results of the barrier removal prioritization show that initial projects targeted for mitigation create much greater improvements in connectivity per unit cost than later projects. Benefit–cost curves from this type of analysis can be used to evaluate potential projects within and among watersheds and minimize overall expenditures for specified restoration targets. Copyright © 2014 John Wiley & Sons, Ltd.     

River widening: an approach to restoring riparian habitats and plant species

‘River widenings’ are commonly used in river restoration to allow channel movement within a spatially limited area. Restoration seeks to restore fluvial processes and to re‐establish a more natural riparian community. This study investigates the performance of five river widenings in Switzerland, focusing on the re‐establishment of riparian (semi‐)terrestrial habitats and species, and highlights some factors that seem to influence their performance. The restoration projects are compared with pre‐restoration conditions and near‐natural conditions, which are assumed to represent the worst‐ and best‐case conditions along a gradient of naturalness. Fuzzy ordination of vegetation data and calculation of landscape metrics based on habitat maps revealed marked differences between the degree of naturalness achieved by each individual restoration project. However, in general river widenings were found to increase the in‐stream habitat heterogeneity and enhanced the establishment of pioneer habitats and riparian plants. Analyses of species pools based on a hierarchic list of indicator species and correspondence analysis showed that the ability of river widenings to host typical riparian species and to increase local plant diversity strongly depends on the distance to near‐natural stretches. Species dispersal and establishment might be hampered by decisions taken outside the scope of the restoration project. Therefore we conclude that action on the catchment scale is needed to maximize the benefits of local management. Copyright © 2005 John Wiley & Sons, Ltd.     

Hydraulic and Physical Structure of Runs and Glides Following Stream Restoration

Hydraulic units are often linked to ecological habitat through geomorphic structure, and a better understanding of the turbulent characteristics of the units is needed. Our work examined the near‐bed turbulent structure of runs and glides in a restored river and investigated the physical characteristics that influenced the near‐bed hydraulics in these units. The research was completed in three restored reaches and one reference reach at the Virginia Tech Stream Research, Education, and Management Laboratory. The laboratory is unique because three different restoration treatments were applied contiguously along a stream, and the restoration practices ranged from passive to active. The passive reach included cattle exclusion, while the active reaches included cattle exclusion as well as vegetation plantings, bank sloping and the construction of inset floodplains. Three‐dimensional velocities were measured near the channel bed in run and glide biotopes within the three restored reaches, as well as an upstream reference reach. The velocities were utilized to analyse and compare near‐bed turbulent structure across the reaches. While the restoration activities did not address the channel bed directly, differences in physical structure of the two physical biotopes were observed among restoration treatments, likely because of changes in bank shape and roughness due to vegetation differences. Differences between reference and restored reaches were still evident approximately 3 years after cattle exclusion and construction activities. Few differences were observed in the hydraulic structure between runs and glides, and the near‐bed flow structure in both runs and glides was related to local roughness. Copyright © 2016 John Wiley & Sons, Ltd.     

Patterns of species richness and introduced species in native freshwater fish faunas of a Mediterranean‐type basin: the Guadiana River (southwest Iberian Peninsula)

In this study, we analysed the factors affecting species richness and introduced species component patterns in native fish faunas of 30 streams of the Middle Basin of the Guadiana River. From a principal component analysis and a stepwise multiple regression analysis performed on a data matrix composed of ten hydrological and biotic variables, we showed that: (1) fish species richness increased with stream length and watershed area, (2) the number of native species in a stream declined as channelizations and river regulation (constructions of dams) are higher, whereas introduced species increased in the same way, (3) the two main negative factors affecting native ichthyofaunas affected dissimilar ecological areas: channelizations, which depend on land‐use intensity of floodplain, mainly occurred in lower reaches of streams, but construction of dams mainly took place in upper sections of rivers, (4) the length of the remaining well‐preserved reaches in a stream appeared to be the only factor accurately predicting native fish species richness, and (5) native fish faunas of small isolated streams are more vulnerable to habitat alteration than those of large streams. Both isolation and fragmentation of populations were recorded, so the conservation status of native and highly endemic fish fauna of the study area is extreme. Protection of the few still extant, well‐preserved small streams and upper reaches, habitat restoration of channeled areas, and inclusion of the need for native fish fauna conservation in long‐term public planning of water use become a priority. Fish communities appear to be a sensitive indicator of biological monitoring to assess environmental degradation. Copyright © 2001 John Wiley & Sons, Ltd.     

RESTORING SALMON HABITAT FOR A CHANGING CLIMATE

An important question for salmon restoration efforts in the western USA is ‘How should habitat restoration plans be altered to accommodate climate change effects on stream flow and temperature?’ We developed a decision support process for adapting salmon recovery plans that incorporates (1) local habitat factors limiting salmon recovery, (2) scenarios of climate change effects on stream flow and temperature, (3) the ability of restoration actions to ameliorate climate change effects, and (4) the ability of restoration actions to increase habitat diversity and salmon population resilience. To facilitate the use of this decision support framework, we mapped scenarios of future stream flow and temperature in the Pacific Northwest region and reviewed literature on habitat restoration actions to determine whether they ameliorate a climate change effect or increase life history diversity and salmon resilience. Under the climate change scenarios considered here, summer low flows decrease by 35–75% west of the Cascade Mountains, maximum monthly flows increase by 10–60% across most of the region, and stream temperatures increase between 2 and 6°C by 2070–2099. On the basis of our literature review, we found that restoring floodplain connectivity, restoring stream flow regimes, and re‐aggrading incised channels are most likely to ameliorate stream flow and temperature changes and increase habitat diversity and population resilience. By contrast, most restoration actions focused on in‐stream rehabilitation are unlikely to ameliorate climate change effects. Finally, we illustrate how the decision support process can be used to evaluate whether climate change should alter the types or priority of restoration actions in a salmon habitat restoration plan. Copyright © 2012 John Wiley & Sons, Ltd.     

The impact of small physical obstacles on the structure of freshwater fish assemblages

Many studies have assessed the effects of large dams on fishes but few have examined the effects of small obstacles. Fishes were sampled and environmental variables were characterized at 28 sites in two Iberian streams, 14 located immediately downstream, upstream and between five small obstacles at river Muge and 14 at river Erra, considered as the reference stream. Multivariate analysis indicated that habitat variables like current velocity and depth, but not physicochemistry, were mainly responsible for site groups' discrimination in both streams. The reference stream exhibited a longitudinal gradient of current velocity that, however, was not strong enough to cause significant changes in the fish assemblage's composition and structure. By successive and drastically repeating this gradient near each structure, the obstacles stream presented differences in fish fauna between the three site types. Lentic upstream sites presented higher density of limnophilic, omnivorous and exotic species, like gudgeon Gobio lozanoi, which are well adapted to this type of habitat. Downstream and between obstacles sites were characterized by the dominance of rheophilic and invertivorous taxa, especially barbel Luciobarbus bocagei. Richness metrics did not differ among site types, but diversity was higher in sites located between the obstacles away from its direct influence, where the habitat diversity was higher. Contrarily to upstream sites, downstream and between obstacles sites were similar in many of the studied features to the reference stream, implying that this type of structures cause a higher modification in the upstream fish community. This study suggests that the effects of small obstacles on habitat and fishes are similar, in some extent, to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts. Copyright © 2009 John Wiley & Sons, Ltd.     

EVALUATION OF RIPARIAN HABITAT RESTORATION IN A LOWLAND RIVER

For many years, navigable lowland rivers have been embanked artificially or suffered from substantial shipping wave action, leading to habitat degradation. Recently, riparian habitats were restored by creating foreshores and spawning grounds in the river Yser, a lowland river in Flanders, Belgium. The aim of this paper was to evaluate the role of these restored habitats for spawning and nursery of juvenile fish. To cover a wide range of anthropogenic disruption, four riparian mesohabitat types were selected and compared, ranging from semi‐natural over artificial spawning grounds and foreshores to artificial embankments. Juvenile fish were subjected to sampling by using electrofishing between June and September 2009 at different microhabitats located in five sites of each riparian mesohabitat type. Juvenile fish strongly preferred natural riparian habitats, whereas artificial embankments showed the lowest species richness, abundance and functional organization of juvenile fish species. Restored riparian habitats appeared to be an appropriate alternative for artificial embankments in navigable lowland rivers but still score significantly less than natural habitats. Juvenile fish avoided bare microhabitats but did not prefer any other microhabitat type (reed, woody or grassy vegetation), emphasizing the importance of microhabitat diversity. This paper provides valuable insights into riparian habitat restoration to river managers and stakeholders. Copyright © 2011 John Wiley & Sons, Ltd.     

Body mass and growth of overwintering brown trout in relation to stream habitat complexity

In winter, juvenile salmonids hide within the substrate during the day and emerge to feed on drifting invertebrates at night. In channelized streams, where the streambed heterogeneity has been artificially reduced, suitable microhabitats (low‐flow refugia) may be in short supply. Therefore, restoration of stream habitat by enhancement structures might improve the overwintering conditions of juvenile salmonids. We used a set of artificial streams to test whether individually‐marked juvenile brown trout of two age‐classes (age‐0 and age‐1 trout) loose mass during the winter differently in channelized and semi‐natural streams. Fish of both age‐classes lost mass early in the winter (November to January), but age‐0 fish in the channelized streams lost more of their initial mass than did the restored‐stream fish (ca. 10% vs. 2.5% on average, respectively). They then exhibited zero‐growth in both treatments in late winter (January to April), and by early spring (May), the channelized‐stream fish had completely caught up for their greater initial mass loss. In control tanks where the fish were fed continuously, age‐0 trout exhibited zero‐growth from November to January, then gaining mass constantly through the rest of the experiment. Significant time*treatment interaction was also detected for age‐1 trout, but all differences were caused by the faster growth of fish in the control tanks, whereas the two channel treatments did not differ significantly. The shortage of suitable sheltering sites in the channelized streams apparently intensified competition and caused greater initial mass loss in age‐0 trout. Furthermore, growth compensation exhibited by juvenile trout may have negative impacts on the long‐term fitness of individuals. Therefore, by increasing the amount of sheltering sites, in‐stream restoration may have potential to enhance the overwintering success of juvenile salmonids. Copyright © 2010 John Wiley & Sons, Ltd.     

Longitudinal changes in macroinvertebrate assemblages in the Meuse River: anthropogenic effects versus natural change

A collaborative study among three nations (France, Belgium, Netherlands) along the Meuse River developed a consistent approach for collecting and interpreting macroinvertebrate data. Specific mesohabitats were sampled in 16 locations along an 800‐km stretch of this lowland regulated river. The objective was to assess the ‘river health’ using macroinvertebrate communities as indicators of biological and ecological variation in space. The main changes in assemblages were investigated using multimetric and multivariate approaches. The authors examined relationships between faunal variations and both physico‐chemical gradients and man‐made disturbances. We related species traits to faunal changes and habitat characteristics. Both a gradual shift from a macroinvertebrate assemblage dominated by insects to a community dominated by crustaceans and molluscs and a drastic decrease in biotic index values were observed along the longitudinal gradient. Taxa were distributed according to oxygen, nitrate and ammonium concentrations, pH, conductivity and summer hydraulic conditions. But major faunal differences among sites could not be explained simply by physico‐chemical variables. The trait analysis underlined the role of temporary habitats in structuring the summer macroinvertebrate community of sites of the uppermost French sector, which supported the most diverse community in terms of trait combination. Downstream the macroinvertebrate community exhibited a more simple and less stable functional organization. We concluded that the Meuse River exhibited both a high biodiversity and a ‘reasonably good’ water quality in the upper reaches. Two transition zones highlighted the influence of a high degree of human impact on stream integrity. Regulation for navigation, ship traffic and heavily polluted effluent discharges influenced instream conditions via multiple processes determining a decline of both habitat stability and diversity. However, the rare occurrence of habitat‐sensitive species in the lower reaches indicated that a partial recovery of communities may be predicted if restoration and protection of disturbed (especially riparian) habitats are fulfilled. Copyright © 2002 John Wiley & Sons, Ltd.     

Spatial distribution and geomorphic condition of fish habitat in streams: an analysis using hydraulic modelling and geostatistics

Reach‐scale physical habitat assessment scores are increasingly used to make decisions about management. We characterized the spatial distribution of hydraulic habitat characteristics at the reach and sub‐reach scales for four fish species using detailed two‐dimensional hydraulic models and spatial analysis techniques (semi‐variogram analyses). We next explored whether these hydraulic characteristics were correlated with commonly used reach‐scale geomorphic assessment (RGA) scores, rapid habitat assessment (RHA) scores, or indices of fish biodiversity and abundance. River2D was used to calculate weighted usable areas (WUAs) at median flows, Q₅₀, for six Vermont streams using modelled velocity, depth estimates, channel bed data and habitat suitability curves for blacknose dace (Rhinichthys atratulus), brown trout (Salmo trutta), common shiner (Notropis cornutus) and white sucker (Catostomus commersoni) at both the adult and spawn stages. All stream reaches exhibited different spatial distributions of WUA ranging from uniform distribution of patches of high WUA to irregular distribution of more isolated patches. Streams with discontinuous, distinct patches of high score WUA had lower fish biotic integrity measured with the State of Vermont's Mixed Water Index of Biotic Integrity (MWIBI) than streams with a more uniform distribution of high WUA. In fact, the distribution of usable habitats may be a determining factor for fish communities. A relationship between predicted WUAs averaged at the reach scale and RGA or RHA scores was not found. Future research is needed to identify the appropriate spatial scales to capture the connections between usable patches of stream channel habitat. Copyright © 2008 John Wiley & Sons, Ltd.