Temporal changes in benthic macroinvertebrates and their interactions with fish predators after restoration in the Cheonggyecheon,a downtown stream in Seoul,Korea

The Cheonggyecheon (Cheonggye stream), a downtown stream in Seoul, Korea, was restored by the historic Cheonggyecheon Restoration Project (2003–2005), and its discharge and other environmental conditions are artificially regulated throughout the year. The aim of this study was to assess temporal changes in benthic macroinvertebrates and their interactions with fish predators in the Cheonggyecheon. Sampling was conducted twice a year (spring and autumn) at three sections of the stream from 2006 to 2010 using a Surber sampler (50 × 50 cm) for benthic macroinvertebrates and a cast net (mesh size, 10 × 10 mm) and a kick net (mesh size, 5 × 5 mm) for fishes. Analyses of annual precipitation and most water quality parameters showed no significant differences across the study period (P > 0.05). The species richness and density of benthic macroinvertebrates and fishes varied across the sampling period. Analyses of functional feeding groups and trophic guilds showed distinct trends, such as an increase in the number of insectivorous fish in the absence of invertebrate predators. Correlation and regression analyses for five major groups of benthic macroinvertebrates and fishes demonstrated that the density of certain groups of benthic macroinvertebrates (e.g. Tubificidae, Erpobdellidae, Baetidae, and Chironomidae) and insectivorous fishes (e.g. Gobioninae, Leuciscinae, Danioninae, and Gobiidae) were negatively correlated. In conclusion, in an artificially regulated stream like the restored Cheonggyecheon, where physical environments are nearly unchanged, fish predation can be a major factor controlling benthic macroinvertebrate communities.     

Relationships between stream acidity and bacteria,macroinvertebrates, and fish: a comparison of north temperate and south temperate mountain streams,USA

A comparative study of relationships between stream acidity and bacteria, macroinvertebrates, and fish in the Adirondack Mountains of upper New York state and in the Southern Blue Ridge Mountains of eastern Tennessee, USA, was conducted. Although the study sites in both regions spanned a pH range from approximately 4.5 to 6.4, considerably greater seasonal variability in pH and higher monomeric Al concentrations characterized the Adirondack sites. Relationships between several biological characteristics and stream water acidity were similar in both regions, including lower production of epilithic bacteria and bacteria on decomposing leaves, lower leaf decomposition rates, lower density and generic richness of scraper/grazer macroinvertebrates, particularly Ephemeroptera, and lower fish abundance and survival in more acidic streams. Densities of total macroinvertebrates and densities of macroinvertebrates and bacteria inhabiting or closely associated with stream sediments were generally not related to stream water acidity.Regional differences occur in some of the relationships between biological characteristics and stream water acidity. Negative correlations between bacterial production on rocks and pH, between bacterial production on decomposing leaves and pH, and between densities of Ephemeroptera and scrapers and pH were stronger in the Adirondacks than in the Southern Blue Ridge. Higher Al concentrations in the Adirondacks may be responsible for the stronger relationships with pH there. The steeper slopes of the relationships between Ephemeroptera density and all forms of Al in the Adirondacks compared with the Southern Blue Ridge suggests that there may be some adaptation among a few acid/aluminum-tolerant species in the seasonally more constant acidic Southern Blue Ridge streams. Fish bioassays indicated longer survival times in acidic streams in the Adirondacks compared with the Southern Blue Ridge, but these results may be an artifact associated with the use in the Southern Blue Ridge of rainbow trout as the test species which is known to be more acid sensitive compared with brook trout, the test species used in the Adirondacks.     

Geomorphology and fish assemblages in a Piedmont river basin, U.S.A.

1. We investigated linkages between fishes and fluvial geomorphology in 31 wadeable streams in the Etowah River basin in northern Georgia, U.S.A. Streams were stratified into three catchment sizes of approximately 15, 50 and 100 km², and fishes and geomorphology were sampled at the reach scale (i.e. 20–40 times stream width). 2. Non‐metric multidimensional scaling (NMDS) identified 85% of the among‐site variation in fish assemblage structure and identified strong patterns in species composition across sites. Assemblages shifted from domination by centrarchids, and other pool species that spawn in fine sediments and have generalised food preferences, to darter‐cyprinid‐redhorse sucker complexes that inhabit riffles and runs, feed primarily on invertebrates, and spawn on coarser stream beds. 3. Richness and density were correlated with basin area, a measure of stream size, but species composition was best predicted (i.e. |r| between 0.60–0.82) by reach‐level geomorphic variables (stream slope, bed texture, bed mobility and tractive force) that were unrelated to stream size. Stream slope was the dominant factor controlling stream habitat. Low slope streams had smaller bed particles, more fines in riffles, lower tractive force and greater bed mobility compared with high slope streams. 4. Our results contrast with the ‘River Continuum Concept’ which argues that stream assemblages vary predictably along stream size gradients. Our findings support the ‘Process Domains Concept’, which argues that local‐scale geomorphic processes determine the stream habitat and disturbance regimes that influence stream communities.     

Short-term recovery of benthos following disturbance from stream habitat rehabilitation

The recovery of benthic macroinvertebrates after disturbance from stream rehabilitation was studied in the River Livojoki, northern Finland. The stream that had been channelized for log transport was rehabilitated on 1 July 1992 by digging holes and inserting boulders. We measured habitat characteristics and sampled benthic animals before and after rehabilitation, including an unrehabilitated control site. The immediate effect of rehabilitation was a slight decrease in the abundances of benthic insects. Recolonization occurred rapidly, within 10 days. Disturbance of the rehabilitation did not have a detectable effect on the macroinvertebrate community. Most species-level changes and community patterns reflected seasonal life history events. Timing of such rehabilitation work can be critical for the recovery rate, which depends on the colonization abilities of the species present after disturbance. We suggest that many disturbances (including minor floods and moderate rehabilitation procedures) may have only small, short-term effects on benthic communities. We emphasize the importance of considering seasonality in studies of disturbance in streams.     

Influence of herbaceous riparian buffers on physical habitat, water chemistry, and stream communities within channelized agricultural headwater streams

Herbaceous riparian buffers (CP 21 grass filter strips) are a widely used agricultural conservation practice in the United States for reducing nutrient, pesticide, and sediment loadings to agricultural streams. The ecological impacts of herbaceous riparian buffers on the channelized agricultural headwater streams that are common throughout the midwestern United States have not been evaluated. We sampled riparian habitat, geomorphology, instream habitat, water chemistry, fishes, and amphibians for 4 years from three channelized agricultural headwater streams without herbaceous riparian buffers and three channelized streams with herbaceous riparian buffers in central Ohio. Only seven of 55 response variables exhibited differences between buffer types. Riparian widths were greater in channelized headwater streams with herbaceous riparian buffers than streams without herbaceous riparian buffers. Percent insectivores and minnows were greater in channelized streams without herbaceous riparian buffers than streams with herbaceous riparian buffers. Percent clay, turbidity, specific conductance, and pH differed between buffer types only during one sampling period. No differences in geomorphology and amphibian communities occurred between buffer types. Our results suggest channelized agricultural headwater streams with and without herbaceous riparian buffers are similar physically, chemically, and biologically. Installation of herbaceous riparian buffers alone adjacent to channelized agricultural headwater streams in central Ohio and other parts of the midwestern United States may only provide limited environmental benefits for these stream ecosystems in the first 4-6 years after establishment. Alternative implementation designs combining the use of herbaceous riparian buffers with other practices capable of altering nutrient and pesticide loads, riparian hydrology, and instream habitat are needed.     

Environmental and spatial controls of taxonomic versus trait composition of stream biota

相似文献   

Submerged undercut banks as macroinvertebrate habitat in a subalpine meadow stream

We compared macroinvertebrate samples from submerged undercut banks with samples from rifles and pools in a low-gradient-meadow reach of a small stream on the Snowy Range, southeastern Wyoming, from July to September 1985. Macroinvertebrates collected from submerged undercut banks were similar to those collected from riffles and pools, but densities varied among the three habitat types. In July Ephemeroptera, Plecoptera, Trichoptera, Coleoptera, and Diptera, as well as Hydracarina, were all substantially more numerous in samples from undercut banks than from riffles or pools. By contrast in September little difference was observed in the abundance of macroinvertebrates in samples from submerged undercut banks, riffles and pools. While forming only 8.5% of the area of aquatic habitat within the study reach submerged undercut banks were estimated to contain 44% of the aquatic insects in July and 30% in August. Further, submerged undercut banks are macroinvertebrate habitat in this subalpine meadow stream, contributing to overall macroinvertebrate abundance and probably an additional food source for trout.     

You don’t belong here: explaining the excess of rare species in terms of habitat,space and time

Ecological communities are composed of a few common and several rare species. Many studies have evaluated the shape of abundance distribution curves, but few studies have assessed the causes of rarity. Using a dataset of stream macroinvertebrates, we investigated whether the excess of rare species in three focal communities of stones in riffles were common 1) in other habitats at the same stream site and period of sampling (environment), 2) in other stream sites in the same habitat and period of sampling (space), and 3) in other years in the same stream site and habitat (time). We observed that around 28% of the rare species were common in other habitats (environment), stream sites (space) or years (time). Among the three factors, rarity was mostly explained by habitat type, whereas a significant portion of the rare species in riffles were common in pools, submerged roots of terrestrial plants or in partially submerged moss patches. This result suggests that the presence in non‐optimum habitat is a strong determinant of the rarity observed in natural communities and most rare species are due to sampling artifacts or accidentally sampled transient species.     

Community–habitat relationships in coastal streams in Big Sur, California, USA: travertine influences macroinvertebrate abundance and community structure

Travertine deposition occurs in streams worldwide but its effects on stream communities are poorly understood. I sampled benthic macroinvertebrates, periphyton, and reach-scale environmental variables in coastal streams in Big Sur, central California, USA, to determine the specific effects of travertine that occurred at some sites as well as to provide a broader assessment of community–habitat relationships. Total density and biomass of macroinvertebrates varied 6- and 9-fold across sites, respectively, and chlorophyll a concentrations varied 10-fold, but invertebrate and periphyton abundances were not correlated. Baetis tricaudatus (Ephemeroptera), Simuliidae (Diptera), and Chironomidae (Diptera) dominated macroinvertebrate communities across all sites, although differences in the relative abundances of these and other taxa produced moderate variation in community structure among sites (Bray-Curtis similarity coefficients of 47–84). Variation in community structure was related to a number of habitat features, notably travertine but also including variables reflecting channel morphology, flow, substrate size, and riparian tree type. Median density and biomass of macroinvertebrates were more than twice as high at sites without travertine than sites with travertine. Taxa richness also was higher at sites without travertine, and community structure differed moderately between sites with and without travertine, although there were no particular assemblages associated with either group. Non-metric multidimensional scaling (MDS) and cluster analysis of similarities in community structure appeared to separate sites with either travertine or high fines from sites without those conditions. These results demonstrate that travertine can have strong effects on stream communities, and additional studies are needed to identify the full range of effects on ecosystems and to evaluate the potential consequences of travertine for conservation efforts such as biomonitoring programs and threatened species management. Handling editor: R. Bailey     

Spatial and temporal variability of macroinvertebrates in spawning and non-spawning habitats during a salmon run in Southeast Alaska

Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream.     

Identification of predominant environmental factors structuring stream macroinvertebrate communities within a large agricultural catchment

• 1 Patterns of macroinvertebrate community composition were examined in streams within a 40000-km² catchment in central Michigan, U.S.A., to identify the major environmental gradients influencing community variation. Agriculture and associated clay and sandy soils predominated in much of the region.
• 2 Eighty macroinvertebrate taxa were collected from stream surveys conducted during May and August 1990. Community composition varied primarily by the proportions of Plecoptera and Ephemeroptera. Benthic communities from the heaviest agricultural zones were most different from those at other sites.
• 3 Chemical composition among the sites varied most in relation to nutrients (NH₃, NO3, PO₄). Other parameters were relatively similar. Physical characteristics of the sites were scored in six habitat categories: (i) substrate characteristics, (ii) instream cover, (iii) channel morphology, (iv) riparian zone and stream-bank conditions, (v) riffle/run quality, (vi) pool quality. Most physical habitat scores were lowest in the intense agriculture zones.
• 4 The relative importance of physical and chemical variables in explaining variation in macroinvertebrate communities was quantified using canonical correspondence analysis. Substrate characteristics were most important in both surveys. Significant correlations (P<0.05 and P<0.10) were observed between substrate quality and total numbers of Ephemeropteran, Plecopteran, and Trichopteran taxa. These relationships reflected correlations from sites in the clay soil-type region (P<0.01 and P<0.10) which contrasted with non-significant results from the less impacted, sandy soil-type region.
• 5 Effective stream restoration efforts in this region will require the alteration of local land-use activities that influence the physical habitat. Further development of empirical relationships between catchment activities and substrate and channel characteristics within natural geomorphic regions is essential for the evaluation of restoration projects.

     

Habitat use by the fish assemblages of two chalk streams

Patterns of habitat use by fish assemblages in two chalk streams in southern England were examined to identify species preferences with respect to major habitat gradients. Both study sites, although differing in some physical habitat characteristics, mainly channel width, water temperature and instream cover, could be arranged similarly along a continuum extending from erosional to depositional habitats. Twelve fish species were collected from stream surveys conducted during July 1993. The habitat was partitioned into six fish species associations that could be assigned to three habitat guilds: depositional ( Barbatula barbatula, Gasterosteus aculeatus and Anguilla anguilla ), riffle ( Leuciscus leuciscus, Thymallus thymallus and Salmo salar ) and generalist ( Salmo trutta, Phoxinus phoxinus, Gobio gobio, Cottus gobio, Lampetra planeri and Pleuronectes flesus ). At low to moderate densities the different species associations were collected in the same habitat patch, but at higher densities there was a clear tendency to mutual avoidance. In particular, large trout appeared as strong interactors that tended to exclude other species from their territories. It is hypothesized that the fish assemblage of the Mill Stream and Bere Stream have partitioned the habitat in such a way as to minimize potential Competition.     

Biological quality metrics: their variability and appropriate scale for assessing streams

The concept of spatial scale is at the research frontier in ecology, and although focus has been placed on trying to determine the role of spatial scale in structuring communities, there still is a further need to standardize which organism groups are to be used at which scale and under which circumstances in environmental assessment. This paper contributes to the understanding of the variability at different spatial scales (reach, stream, river basin) of metrics characterizing communities of different biological quality elements (macrophytes, fishes, macroinvertebrates and benthic diatoms) as defined by the Water Framework Directive. For this purpose, high-quality reaches from medium-sized lowland streams of Latvia, Ecoregion 15 (Baltic) were sampled using a nested hierarchical sampling design: (river basin → stream → reach). The variability of metrics within the different groups of biological quality elements confirmed that large-bodied organisms (macrophytes and fish) were less variable than small-bodied organisms (macroinvertebrates and benthic diatoms) at reach, stream and river basin scales. Single metrics of biological quality elements had the largest variation at the reach scale compared with stream and basin scales. There were no significant correlations between biodiversity indices of the different organism groups. The correlation between diversity indices (Shannon’s and Simpson’s) of the biological quality elements (macrophytes, fish, benthic macroinvertebrates and benthic diatoms) and a number of measured environmental variables varied among the different organism groups. Relationships between diversity indices and environmental factors were established for all groups of biological quality elements. Our results showed that metrics of macrophytes and fish could be used for assessing ecological quality at the river basin scale, whereas metrics of macroinvertebrates and benthic diatoms were most appropriate at a smaller scale.     

Assessment of the relationships of geographic variation in species richness to climate and landscape variables within and among lineages of North American freshwater fishes

Aim Geographic variation in species richness is a well‐studied phenomenon. However, the unique response of individual lineages to environmental gradients in the context of general patterns of biodiversity across broad spatial scales has received limited attention. The focus of this research is to examine relationships between species richness and climate, topographic heterogeneity and stream channel characteristics within and among families of North American freshwater fishes. Location The United States and Canada. Methods Distribution maps of 828 native species of freshwater fishes were used to generate species richness estimates across the United States and Canada. Variation in species richness was predicted using spatially explicit models incorporating variation in climate, topography and/or stream channel length and stream channel diversity for all 828 species as well as for the seven largest families of freshwater fishes. Results The overall gradient of species richness in North American freshwater fishes is best predicted by a model incorporating variables describing climate and topography. However, the response of species richness to particular climate or landscape variables differed among families, with models possessing the highest predictive ability incorporating data on climate, topography and/or stream channel characteristics within a region. Main conclusions The correlations between species richness and abiotic variables suggest a strong influence of climate and physical habitat on the structuring of regional assemblages of North American freshwater fishes. However, the relationship between these variables and species richness varies among families, suggesting the importance of phylogenetic constraints on the regulation of geographic distributions of species.     

Two Newly Recorded Species of tribe Eucosmini (Lepidoptera,Tortricidae) from North Korea

Stream restoration affects stream biodiversity by improving water quality and habitat environments. Benthic macroinvertebrates are used as indicators of changes in stream environment, and, therefore, the effects of restoration can be evaluated by a long‐term monitoring of benthic macroinvertebrates. Cheonggye stream is an urban stream in Seoul, Korea, and a restoration project was conducted from July 2003 to September 2005. The purpose of this study was to investigate the long‐term changes in the benthic macroinvertebrate communities in Cheonggye stream after the restoration project in 2005. A 6‐year field study was seasonally conducted at five study sites in Cheonggye stream from November 2005 to October 2011. Benthic macroinvertebrates were sampled quantitatively using a Surber sampler (50 × 50 cm; mesh 0.25 mm, two replications per site). As a result, species richness of benthic macroinvertebrates rapidly increased after the restoration project and peaked (35 species per sample) in 2006 but gradually dropped to approximately 20 species up to the recent year. As a consequence, community indices changed gradually according to species richness and abundance: Dominance indices peaked in 2010 and species diversity indices (H') peaked in 2007. According to a functional feeding group analysis, the composition of collector–filterers increased at first, but the decreased gradually to the recent year. In contrast, collector–gatherers showed an opposite tendency. The composition of clingers increased during the initial 4 years (2005–2008), whereas burrowers rapidly increased after 2008.     

Different roles of environmental variables and spatial factors in structuring stream benthic diatom and macroinvertebrate in Yangtze River Delta,China

Exploring the relative contribution of spatial factors and environmental variables in shaping communities is of widespread interest in biodiversity conservation and environmental management. Stream communities are hierarchically regulated by environmental variables over multiple spatial scales, and the reaction of different organisms to stressors are still equivocal. We sampled both macroinvertebrates and diatom at 80 sites and additional 10 sites for macroinvertebrates, field measured and laboratory analyzed environmental variables, from the tributaries of Qiantang River, Yangtze River Delta China in 2011. We used PCNM (principal coordinates of neighbor matrices) to generate spatial predictors. We applied redundancy analysis and variation partitioning procedures to identify key spatial and environmental factors, and to quantify their relative roles in shaping diatom and macroinvertebrate assemblages. Our results demonstrated the role of spatial and environmental variables differed in shaping benthic diatom and macroinvertebrate. Diatom assemblage variations were better explained by spatial factors, however macroinvertebrate assemblage variations were better explained by environmental variables. In terms of environmental variables, catchment scale variables (e.g., land use estimators, land use diversity) played the primary role in determining the patterns of both diatom and macroinvertebrate assemblages, whereas the influence of reach-scale variables (e.g., pH, substrates, and nutrients) appeared less. However, nutrients were the stronger factors influencing benthic diatom, whereas physical habitat (e.g., substrates) played more important role than water chemistry in structuring macroinvertebrates. Our results provided more evidence to the incorporation of spatial factors interpreting spatial patterns of stream organisms, and highlighted the useful of multiple organisms and environmental variables at different spatial scales in diagnosing mechanism of stream degradation and in building a sound stream conditions monitoring program for Yangtze River Delta.     

Juvenile coho salmon track a seasonally shifting thermal mosaic across a river floodplain

相似文献   

Restoration of macroinvertebrates,fish, and habitats in streams following mining subsidence: replicated analysis across 18 mitigation sites

Human activities have led to declines in stream functioning and stream restoration seeks to reverse this trend. Longwall coal mining, an underground full‐extraction method, can cause surface subsidence, affecting streams by creating a series of deep pools that trap sediment, reduce habitat diversity, and impair macroinvertebrate and fish communities. Mining effects on streams must be mitigated to maintain the functions, values, and foreseeable uses of streams. Gate cutting is a procedure that alleviates pooling by reestablishing the stream grade, accompanied by procedures that stabilize the channel, restore substrates, and enhance in‐stream and riparian habitats. We evaluated effectiveness of gate cuts at restoring streams affected by subsidence pooling at 18 independent restoration sites over two mines in southwestern Pennsylvania, U.S.A. At each site, sampling stations were established to monitor effects of mining subsidence and its restoration on macroinvertebrates, fish communities, and habitats. We tested for effects of sequential interventions (subsidence and restoration) on biological and habitat variables in a replicated before–after design, controlling for potentially confounding temporal effects (sample month and antecedent effective precipitation). All biological indices and substrate‐related habitat indices declined following subsidence but improved following restoration. Macroinvertebrate indicex and taxa richness, substrates, and riparian vegetation continued to improve with time following restoration. Whereas other studies have concluded that biological communities may take many years to respond to restoration, these results indicate that where macroinvertebrate and fish communities are altered by subsidence pooling, they can be effectively restored using gate cuts to pre‐mining levels within relatively short time periods.     

Quantification of submerged wood in a lowland Australian stream system

1. The importance of submerged wood (snags) as macroinvertebrate habitat was evaluated in the Pranjip-Creightons Creek system, a lowland stream system in northern Victoria. Snag surface area and biomass were measured at ten sites along the system. The first four upstream sites, located in the foothills of the Strathbogie Ranges, and the next three sites, on the northern Victorian riverine plain, were affected by streambank erosion and high sediment loads and contained little instream wood. A further three sites (Sites 8, 9 and 10) downstream on the riverine plain were not as affected by erosion and possessed extensive stands of riparian river redgum, Eucalyptus camaldulensis, which contributed large amounts of wood to the stream channel. 2. Wood quantities at Site 8 were less than at Sites 9 and 10 downstream where the density of riparian redgum was greater. At Sites 9 and 10, snag surface area per m² of stream bed was 0.57–0.92m² and 0.38–0.71m² depending on discharge. Total snag biomass in the stream channel at the same sites was 26 and 41kg m^?2, respectively. Redgum was important to macroinvertebrates as habitat, at one site contributing 25% of total macroinvertebrate densities and over 30% of total macroinvertebrate biomass m^?2 of stream bed. 3. Estimations of nitrogen content and C:N ratios of decayed redgum were carried out to provide information on its putative nutritional quality to xylophagous macroinvertebrates. Decayed redgum wood has a comparatively high N content and therefore a low C:N ratio, but appeared to be unpalatable to most macroinvertebrates. Only two macroinvertebrate species, the chironomid larvae Stenochironomus sp. and Dicrotendipes sp., were found to consume decayed redgum.     

Simple predictions of instream habitat model outputs for fish habitat guilds in large streams

1. In the context of a generalised modification of hydraulic conditions in medium to large streams, modelling the impacts of stream regulation on fish communities in multiple streams is an important challenge for basic and applied freshwater ecology. Conventional instream habitat models such as PHABSIM link a hydraulic model with preference curves for various species to estimate habitat value changes with discharge in stream reaches. Despite world‐wide applications, they have been scarcely used in multiple sites with multiple species. 2. We assigned 21 size classes of European fish species to four habitat guilds (cluster analysis grouping size classes with comparable microhabitat preference curves). Then, we ran a conventional instream habitat model on 28 French stream reaches belonging to the `barbel zone', to estimate habitat values versus discharge curves for the 21 size classes. We summarised the outputs as mean habitat values for guilds, and tested if they were predictable from average characteristics of reaches (discharge, depth, width, particle size). 3. As was obtained elsewhere for populations, habitat values for guilds were strongly related to average, dimensionless characteristics of reaches. The Reynolds number of reaches, equivalent to a discharge per width unit, reflected most of the discharge‐dependent changes in habitat values (within reaches). In particular, habitat values of species preferring bank (respectively midstream) microhabitats decreased (respectively increased) with increasing Reynolds number. The Froude number at median discharge was the major predictor of reach‐dependent but discharge‐independent variations in habitat values. Habitat values of species preferring riffle versus pool or bank microhabitats were higher in reaches with high Froude numbers. These relationships were consistent with existing knowledge on the different species. 4. Such results suggest that the input variables required to estimate habitat values for fish communities can be greatly simplified, as illustrated by a general estimation of the sensitivity of species preferring midstream habitats to discharge changes in any reach. Cost‐efficient alternatives to conventional instream habitat models should facilitate their validation in multiple sites, a point that remains critical in instream habitat modelling of fish communities.