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Freshwater mussels in the family Unionidae are a diverse faunal group in North America. Anthropogenic disturbances have caused many unionid species to be listed as threatened, endangered, o...

Unionid freshwater mussels are one of the most imperilled groups in North America. They play an important role in freshwater ecosystems, both as a food source and as filter feeders. Their priority conservation status has generated interest in unionid research. Here, data from the US Geological Survey was used to produce predictive models of mussel habitat affinities at a resolution of 100 m2 across an area of thousands of square kilometres. This approach correctly identifies areas that are more suitable for threatened mussel species beds as compared with less suitable areas (>97% of the time) Stream segments were identified that are forecast to have high suitability for threatened mussels. Potamilus amphichaenus differed from other threatened mussel species by being associated with a wider range of volumetric flow rates and by not being restricted by the clay content of the soils. Of the species examined, it was the most large-river oriented in habitat use and distribution. These methods can help conservation planners and land-use managers make rational decisions about where to focus their efforts in lotic habitats without the need for intensive environmental measurements while still providing high-resolution information.

Hydrologic processes interact with geomorphic patterns to create the spatial and temporal variation in riverine habitat that affects the distribution of aquatic species throughout stream networks. The process domains concept (PDC) states that longitudinally-abrupt changes in geomorphic processes along streams determine temporal patterns of natural disturbance that influence the distribution of stream organisms. Despite its potential generality, the PDC has been applied primarily to mountain streams of western North America. We tested the utility of the PDC as a conceptual framework for characterizing spatiotemporal variability in abiotic conditions and assessed the influence of process domains (PDs) on community composition of fishes and mussels along a fifth order river mainstem in the gulf coastal plain of the southeastern United States. We measured channel cross sections at three transects nested within three sites nested within three stream reaches to quantify multi-scale spatial variability in channel geomorphology along the mainstem of the Neches River, Texas, USA. Next, we modeled stage-dependent channel hydraulics to quantify temporal variability in habitat area and benthic disturbance. Lastly, we sampled fishes and mussels at each site and tested whether PDs correlate with spatial variation in taxonomic and functional community composition. Channel cross-sectional dimensions varied at the reach scale and affected the modeled temporal variability in habitat area and benthic disturbance. This interaction between channel geomorphology and disturbance regime indicated the presence of distinct PDs at the reach scale. Taxonomic composition of fishes did not differ among reaches, whereas abundance and richness of mussels were strongly reduced in the upper reach compared to the middle and lower reaches. Only slight differences in functional traits of fishes and mussels were apparent among reaches, suggesting that reach scale PDs do not influence community composition via the filtering of these functional traits. This study provides empirical evidence that the PDC is a useful framework for describing hydrogeomorphic conditions and mussel abundance and richness and can guide channel restorations in streams draining regions of low topography.

We evaluated relationships between in-stream habitat, spatial distribution, and geomorphic features at 28 study sites within a predominantly agricultural watershed in Ohio. Objectives were to: (1) measure and compare the physical structure and biotic communities of highly modified drainage channels to those of minimally impacted channels, (2) identify significant environmental factors influencing fish and invertebrate assemblages in modified channels, and (3) relate them to biotic communities in a multivariate statistical model and then to compare fish species and macroinvertebrate taxa models to common multi-metric bioassessment index models. We used canonical correspondence analysis (CCA) and variance partitioning to relate environmental variables to fish and macroinvertebrate community attributes. Geomorphically, minimally impacted sites were statistically different than bench and trapezoidal sites. Bench sites were statistically different than trapezoidal sites in floodplain width and depth ratios indicating that bench formation provided some amount of attached floodplain for the inset channel and functioned more similar to how natural streams would function. Key ecological drivers for macroinvertebrate communities were stream size, gradient and connectivity to a floodplain. Key ecological drivers for fish communities were quality of in-stream habitat variables; however, stream size and connectivity to a floodplain also were important. Larger, perennial sites tended to support more aquatic biota and more diverse assemblages either as primary habitat or as conduits between higher quality upstream or downstream locations. The latter can be critical to sustaining biota in highly modified agricultural watersheds. In smaller systems, in-stream habitat was a limiting factor but, more importantly, they experienced smaller discharges and can become intermittent during dry months. We hypothesized that leaving vegetated benches in the agricultural ditch would improve local ecology, but our data do not support this hypothesis as measured benches were either intermittent or too small to be important fluvial features. In the agriculturally-dominated modified headwater systems studied, we hypothesize that the proximity to a nearby patch of high quality habitat might be the main driving factor.

We characterized coldwater stream fish community response to habitat degradation and channelization for agriculture. Coldwater streams are not common in the lower midwestern United States, and these streams differ from warmwater streams with respect to their diversity and community response to degradation. Six sites were sampled on the coldwater Mac-o-chee Creek in Ohio. Three reaches were classified as geomorphically constrained (by a roadway) and three as recovering (unconstrained and not channelized or cleaned for more than 100 y). Within each reach 31 mesohabitat units were sampled and were delineated as riffles, runs, or pools. Our goals were: (1) to examine how habitat and geomorphic impairment influences the abundance and community structure of coldwater fishes; and (2) to test whether the constraints on recovery from channelization were more influential in structuring communities than mesohabitat types. Our hypothesis was that we would find lower species diversity overall in the recoverin...

Wood in streams functions as fish habitat, but relationships between fish abundance (or size) and large wood in streams are not consistent. One possible reason for variable relationships between fish and wood in streams is that the association of fish with wood habitat may depend on ecological context such as large-scale geomorphology. We studied the relationship between salmonid assemblages and large wood jams (LWJ) in four settings that differed geomorphically at the scale of the stream corridor along a tributary to Lake Superior in old-growth conifer-hardwood forest in northern Michigan. The focal fish species of this study were brook trout (Salvelinus fontinalis), which were wild in the stream. Relocation efforts for coaster brook trout (an adfluvial life history variant of brook trout) were ongoing in the study stream. We measured fish abundance and length in pairs of pools of similar size and substrate, but varying in the presence of LWJ; this allowed us to evaluate associations of fish simply with the presence of LWJ rather than with other channel or flow-shaping functions of LWJ. The length of Oncorhynchus spp. and young introduced brook trout was not strongly correlated with LWJ presence; however, the presence of LWJ in pools was positively correlated with larger wild brook trout. We also found that the correspondence of LWJ with the abundance of salmonids appears to be moderated by the presence of alternative habitat in this relatively natural, old-growth forest stream.

We determined composition and trophic structure of macroinvertebrate assemblages, and also examined how environmental factors, such as riparian forest, aquatic habitat, and vertebrate predators, influenced these assemblages in relatively undisturbed headwater streams of northeastern Ohio. Using canonical correspondence analysis, we examined the relationships between macroinvertebrate assemblages, both compositional and trophic structure, and the environment. Ordination analyses showed a distinct separation of upstream and downstream macroinvertebrate faunas, while variance partitioning suggested that this may be because of the strong effects that predatory fishes and salamanders had in upstream areas. Aquatic habitat may be a strong determinant of macroinvertebrate composition and structure in these headwater streams, though this may be a reflection of site fidelity. Riparian forest habitat also explained a large portion of variation in macroinvertebrate functional feeding guild structure, emphasizing the...

SUMMARY 1. The use of trait-based approaches to examine the ecology of stream fish assemblages is increasing. However, selection of traits that will be useful in testing spatial or temporal hypotheses about ecological organisation is currently limited by availability of data, rather than empirical evaluation. 2. We analysed two data sets of stream fish assemblages to compare taxonomy and traitbased approaches. The Wabash River temporal data set is based on 25 years of boat electrofishing collections over a 230-km river distance. The Indiana Department of Environmental Management data set of stream collections in the state of Indiana was selected to represent a spatial database. We compared several trait-based approaches: reproductive guilds, life history variables, biomonitoring metrics, ecosystem-based functional guilds and feeding and ecosystem interaction guilds. 3. Analyses of fish assemblages that are designed to detect how environmental variation structures fish assemblages can expect similar results using taxonomic or trait-based approaches. Results of trait-based approaches will vary according to the spatial extent of the region and the number of unique entities of trait groups for a given data set. However, taxonomic analyses accounted for more variation than any trait-based analyses.

The determinination of an adequate collection protocol for protists is critical in the examination of their distribution and composition in temperate headwater streams. The objective of this study was to test which sampling design/sample gear combination would yield a cost-effective, site-representative protist assemblage. Defining parameters included greatest taxa richness, abundance, morphological diversity, taxa overlap, and cell-size diversity. Two sample designs (i.e., transect and mesohabitat design) and two sample gears (i.e., benthic grab sample, and a colonizing device [polyurethane foam unit, PFU]) were tested in three 100-m reaches representing the predominant environmental conditions (i.e., fragmented woodlots and agriculture) in the study area. A two-way ANOVA was used to evaluate abundance taxa richness and abundance of the protist assemblage (fixed effects) across the three reaches (random effects). The mesohabitat sampling design had the highest mean in both taxa richness (n = 72, P = 0.0012) and abundance (n = 72, P = 0.0004). The highest mean was reported with the benthic grab sampler (39.89 ± 1.1) in the abundance count only (n = 72, P

The effects of stream size and flow regime on spatial and temporal variability of stream fish distribution, abundance, and diversity patterns were investigated. Assemblage variability and species richness were each significantly associated with a complex environmental gradient contrasting smaller, hydrologically variable stream localities with larger localities characterized by more stable flow regimes. Assemblages showing the least variability were the most species-rich and occurred in relatively large, stable environments. Theory suggests that species richness can be an important determinant of assemblage variability. Although this appears to be true in our system, we suggest that spatial and temporal heterogeneity in the environment largely determines both assemblage richness and variability, providing a more parsimonious explanation for the diversity–variability correlation. Changes in species richness of local assemblages across time were coordinated across the landscape, and assemblages formed spatially and temporally nested subset patterns. These results suggest an important link between local community dynamics and community-wide occurrence. At the species level, mean local persistence was significantly associated with regional occurrence. Thus, the more widespread a species was, the greater its local persistence. Our results illustrate how the integrity of local stream fish assemblages is dependent on local environmental conditions, regional patterns of species distribution, and landscape continuity.

We collected fishes and macroinvertebrates seasonally from eight headwater streams in three different drainage basins (the Red, Calcasieu, and Sabine rivers) crossing Peason Ridge Training Area in west-central Louisiana. Peason Ridge is part of the Fort Polk military training facility. We used multivariate analyses to test the effects of physical variables (i.e., current velocity, depth, and substrate), time (seasonal variability), drainage basin, and military training activities on assemblage structure. Tributaries of the Red River had the highest gradient and were predominated by shallow, swift-flowing runs with sandy substrates. Southern tributaries of the Calcasieu and Sabine rivers were of lower stream gradient and contained deep, sluggish runs and pools with large amounts of woody debris and silt. Fish assemblages were structured primarily by military training and drainage basin. Faunal differences among drainage basins probably reflect differences in stream gradient. Fish assemblages in tr...

In 1990–1992, the United States Forest Service sampled six hydrologically variable streams paired in three different drainage basins in the Ouachita Mountains, Arkansas, U.S.A. Fishes, macroinvertebrates, and stream environmental variables were quantified for each stream. We used these data to examine the relationship between regional faunas (based on taxonomy and trophic affiliation of fishes and macroinvertebrates) and measured environmental variables. Because fishes are constrained to their historically defined drainage basins and many insect taxa are able to cross basin barriers, we anticipated that both groups would respond differently to environmental variability. Fishes were influenced more by environmental variability that was unique to their historical drainage basins, but macroinvertebrates were associated more strongly with environmental variability that was independent of drainage basins. Thus, the individual drainage basins represented a historical constraint on regional patterns of fish assembly. For both fishes and macroinvertebrates, groupings based on taxonomy and trophic affiliation showed a similar response to environmental variability and there was a high degree of association between taxonomic and trophic correlation matrices. Thus, trophic group structure was highly dependent on the taxonomic make-up of a given assemblage. At the basin-level, fish and macroinvertebrate taxa were associated more strongly with environmental variability than the trophic groups, and these results have implications for basin-level studies that use trophic groupings as a metric to assess ecological patterns. Trophic categories may not be a useful ecological measure for studies at large spatial scales.

Despite considerable investigation of stream systems, the influence of fish predation on macroinvertebrate assemblages is still poorly understood and remains a controversial subject. We conducted a field experiment in an intermittent reach of Alum Creek in the Ouachita Mountains, Arkansas, to examine the effects of predatory fish on macroinvertebrate assemblages. We tested the prediction that with pool isolation fish would have a top-down influence on macroinvertebrate assemblages. Overall, fish had a significant effect on both the density and assemblage structure of the macroinvertebrates in isolated stream pools. Assemblage effects may be linked to a feeding preference for relatively rare food items. These patterns were evident despite the loss of replicates (i.e., the drying of individual pools), indicating a strong short-term predator effect. We suggest that the use of different methodologies among studies makes it difficult to determine the influence of fish predation on macroinvertebrate as...

Using Basin Area Stream Survey (BASS) data from the United States Forest Service, we evaluated how timber harvesting influenced patterns of variation in physical stream features and regional fish and macroinvertebrate assemblages. Data were collected for three years (1990-1992) from six hydrologically variable streams in the Ouachita Mountains, Arkansas, USA that were paired by management regime within three drainage basins. Specifically, we used multivariate techniques to partition variability in assemblage structure (taxonomic and trophic) that could be explained by timber harvesting, drainage basin differences, year-to-year variability, and their shared variance components. Most of the variation in fish assemblages was explained by drainage basin differences, and both basin and year-of-sampling influenced macroinvertebrate assemblages. All three factors modeled, including interactions between drainage basins and timber harvesting, influenced variability in physical stream features. Interactions between timber harvesting and drainage basins indicated that differences in physical stream features were important in determining the effects of logging within a basin. The lack of a logging effect on the biota contradicts predictions for these small, hydrologically variable streams. We believe this pattern is related to the large scale of this study and the high levels of natural variability in the streams. Alternatively, there may be time-specific effects we were unable to detect with our sampling design and analyses.

Genetic variation was assessed with protein electrophoresis for seven populations of the leopard darter, Percina pantherina, a species restricted to five rivers in the Little River System of southwestern Arkansas and southeastern Oklahoma. Analysis of genetic diversity indicated that only 10% of the total gene diversity (HT = 0.03) reflects differences among populations; 7.3% was attributable to differences among populations in different rivers and 2.7% to differences among samples within rivers. Average heterozygosity was fairly low (0.020–0.031), but there was a relatively high level of allele diversity with two or more alleles detected at 21 of the 31 gene loci examined. Most polymorphism was due to alleles occurring at low frequencies (≤0.05) in restricted geographic areas. An allele frequency, maximum parsimony analysis revealed three primary clades: (1) populations in Little and Glover rivers, (2) populations from the Mountain Fork River drainage and (3) populations in Robinson Fork and Cos...

We examined fish community structure and habitat correlates at 10 stations on Lagoon Creek, a fifth-order tributary of the Cimarron River in east-central Oklahoma, during spring, summer, and fall 1995. Lagoon Creek is contained within the Sandstone Hills physiographic region, a transition zone between the Redbeds Plains and the Ozark Plateau. We collected 33 species, several of which are “upland” species that may occur nowhere else in the Cimarron River drainage. Longitudinal zonation was evident, with addition of species and increasing species diversity in the downstream direction. Canonical Correspondence Analysis (CCA) identified upstream, midstream, and downstream fish assemblages with the downstream assemblage being the most distinctive. There appeared to be little seasonal effect, indicating that Lagoon Creek may be a more “stable” stream than many other prairie systems.

In February 1996, the United States Department of Agriculture Forest Service completed a renovation project at Horsethief Spring, LeFlore County, Oklahoma. This spring is located on the north face of Winding Stair Mountain along the Talimena Scenic Drive (State Highway 1; T3N R25E Sec. 7). Renovations included paving the existing parking area, installing a restroom facility and picnic site above the spring, resurfacing the existing horse trail that crosses just below the spring origin, reconstructing a stone wall next to the lower parking area, and removing riparian vegetation along the upper portion of the spring. The area of vegetation removal was approximately 0.1 acres. Although this may seem to be a small-scale disturbance, we were concerned about the potential impacts on sensitive salamander species that depend on the spring habitat.

We used the computer program RAMAS to perform a population viability analysis for the leopard darter, Percina pantherina. This percid fish is a threatened species confined to five isolated rivers in the Ouachita Mountains of Oklahoma and Arkansas. A base model created from life history data indicated a 6% probability that the leopard darter would go extinct in 50 years. We performed sensitivity analyses to determine the effects of initial population size, variation in age structure, variation in severity and probability of catastrophe, and migration rate. Catastrophe (modeled as the probability and severity of drought) and migration had the greatest effects on persistence. Results of these simulations have implications for management of this species.