The flow regime is considered a 'master variable' in riverine ecology because it directly influences stream geomorphology and biological communities. However, other environmental and anthropogenic factors have direct and synergistic effects with flow on fish diversity, complicating estimates of the flow regime's true importance. Moreover, most flow-ecology studies focus only on taxonomic diversity (i.e., species), without considering functional (trait-focused) or phylogenetic (evolution-focused) dimensions of diversity. In this study, we used linear regression with variation partitioning to parse out the independent and shared roles of the flow regime, physical environmental factors (e.g., soil characteristics) and the anthropogenic environment (e.g., developed land cover) for structuring multidimensional diversity of 365 stream fish communities in two biogeographic regions across South Carolina, USA. These variables explained between 8% and 18% of total variation of the local diversity. The flow regime contributed to diversity in all cases, but frequently covaried with physical and/or anthropogenic environmental variables. This covariation indicated that the independent role of flow would have been inflated if other environmental variables were not considered. The three dimensions of stream fish diversity were weakly correlated with one another and were associated with different environmental variables, indicating that each of them represents unique and complimentary facets of fish diversity. Accordingly, only considering the independent effects of instream flow on fish diversity may miss meaningful interactions between the flow regime and the other components of the environment that influence biodiversity patterns, leading to over simplified flow-ecology relationships.

The black basses of the southeastern United States are an excellent study group for investigating the relative roles of habitat and biotic interactions for determining species co-occurrence. This group is comprised of generalist species such as Largemouth Bass Micropterus nigricans, as well as specialist species such as those within the M. coosae complex. Bartram's Bass M. sp. cf. coosae is a provisional species of particular concern endemic to the upper Savannah River basin of Georgia, South Carolina and North Carolina, USA. Bartram's Bass and Largemouth Bass may occur in the same rivers, but do not necessarily co-occur in the same micro- or mesohabitats. Recent surveys in numerous Savannah River tributaries where Bartram's Bass was previously known to have existed have either detected only Largemouth Bass or no black basses at all. The apparent loss of endemic Bartram's Bass and frequent replacement with cosmopolitan Largemouth Bass is concerning from a conservation perspective because it could indicate either (a) ongoing biotic homogenisation via habitat shifts, (b) habitat-mediated asymmetric interspecific interactions resulting incompetitive exclusion, or (c) some combination of these processes. In this study, we assessed differences in landscape-level factors and proximity to reservoirs on the occurrence and co-occurrence of these species using a multispecies occupancy model developed for two or more potentially interacting species. This approach can be used to untangle the relative roles that biotic interactions or habitat covariates have on species distributions. The most compelling model evidence suggested that Bartram's Bass and Largemouth Bass were associated with land cover effects on instream habitat and provided less evidence that co-occurrence was driven by interspecific interactions. Human land use change and impoundment of free-flowing rivers have created new opportunities for Largemouth Bass to access upstream lotic habitats and are associated with the loss of lotic habitats and restricted the distribution of Bartram's Bass.

Objective: The goal of this study was to estimate gear-specific detection (electrofishing and angling) and occupancy correlates for endemic Bartram's Bass Micropterus sp. cf. coosae and a suite of other Micropterus species in tributaries to the upper Savannah River of the southeastern United States. Methods: We conducted 669 spatially replicated surveys at 116 wadeable stream sites using backpack electrofishing and angling. We used multistate occupancy models to compare detection between angling and electrofishing and estimate effects of watershed scale human land cover modification and distance to reservoirs on three states of black bass occupancy: no black bass detected (state 0), black bass detected (state 1), and only pure Bartram's Bass detected (state 2, given state 1). We then combined the data from 2021 with a nonreplicated data set collected in 2017-2018 (158 sites total) and used principal coordinates analyses to compare 20 abiotic variables indexing instream flow, human land cover, and other abiotic variables between the two black bass occupancy states. Results: We detected black basses in 114 surveys among 59 sites and only pure Bartram's Bass in 39 surveys among 12 sites. Detection of both occupancy states was higher for backpack electrofishing than for angling. Given that a site was suitable for black bass, the negative effect of developed land cover on occupancy of pure Bartram's Bass was greater at sites within 20 km of a major reservoir. Sites with only pure Bartram's Bass were associated with indicators of natural land cover and a milder flow regime. Conclusions: Maintaining forested land cover and a natural flow regime a top priority for conserving Bartram's Bass. Restoration or reintroduction efforts may be less effective if they are conducted near reservoirs from which nonnatives can easily disperse and colonize. Conducting temporally replicated sampling will allow for better estimates of detection and occupancy.

We describe as new species Micropterus pucpuggy Freeman & Freeman (Bartrams Bass), sp. nov., and Micropterus calliurus Freeman & Freeman (Altamaha Bass), sp. nov., which occur allopatrically in four river systems draining the Atlantic Slope of the southeastern United States. In recent decades, biologists and anglers have acknowledged the existence of these two distinctive taxa of black bass, both of which were previously considered synonymous with M. coosae Hubbs & Bailey (Redeye Bass). However, introgression with non-native congeners that have been widely introduced for sport-fishing (including M. henshalli Hubbs & Bailey and M. dolomieu Lacepde) has confounded formal description of M. pucpuggy and M.calliurus. We examined mitochondrial (mtDNA) and nuclear gene sequences of candidate type-specimens of M. pucpuggy and M. calliurus. We then used reduced-representation, short-read sequencing of candidate types along with specimens of six other Micropterus species to identify a series of non-introgressed individuals for each of the two new species. Micropterus pucpuggy and M. calliurus are each reciprocally monophyletic in both mitochondrial and RADseq phylogenies and are diagnosable from all other Micropterus species and from each other in chromatic fin coloration, body pigmentation, and other morphological attributes.

Bartram's Bass Micropterus sp. cf. coosae is endemic to the Upper Savannah River Basin of the southeastern United States, and is threatened by hybridization with invasive Alabama Bass M. henshalli. Quantifying movement of these species and their hybrids will improve understanding of how nonnative alleles spread among riverine fish populations. We quantified summer/autumn movement of Bartram's Bass, Alabama Bass and hybrid bass in Eastatoee Creek-a tributary experiencing ongoing invasion from Keowee Reservoir. To do this, we first quantified factors associated with the longitudinal distribution and weekly movement rates of each species, then estimated probabilities of species transitioning among key habitats at the river-reservoir interface. We tagged 291 fish with passive integrated transponder tags, sampling the entire stream length of Eastatoee Creek four times in both 2021 and 2022. We radio-tagged an additional 52 fish and tracked them from early May through mid-October each year. We used mixed effect models and a Bayesian multistate model to quantify movement, river position, movement probability and the effects of abiotic factors thereon. Alabama Bass and hybrid bass moved more than Bartram's Bass and remained in the lower reaches of Eastatoee Creek, apparently restricted by a reach of high-gradient habitat that functioned as a natural barrier. Alabama Bass made greater upstream movements during cooler spring temperatures when higher reservoir levels inundated the creek mouth. Bartram's Bass were distributed throughout Eastatoee Creek, making shorter weekly upstream movements associated with increasing temperature in late spring. Movement of hybrid bass from lower portions of tributaries is likely a primary source of nonnative allele spread in this system.

Land use/land cover change from forested to developed land is a major threat to freshwater biodiversity globally. However, existing research has focused on high-density development in urban centers. We know less about how low-density development affects stream biodiversity, even though increases in low-density development have been documented across the globe and may be tied to the homogenization of stream biotic assemblages. Here, we investigated the diversity (alpha and beta) and assemblage composition of algal diatoms and fish over a ten-year period at three points in time (2000, 2005, 2010) in forested watersheds (n = 4) and watersheds experiencing increasing low-density development (“developing watersheds”; n = 4) in the southern Appalachian Mountains of western North Carolina, USA. We employed a repeated snapshot sampling approach for the data collection. In developing watersheds, we observed higher alpha diversity and different species assemblages for both diatoms and fishes compared to forested watersheds. These differences were attributed to the establishment and/or higher abundances of cosmopolitan diatoms (e.g., Achnanthidium rivulare Potapova and Ponader, Navicula spp., Nitzschia spp.) as well as fishes (e.g., Creek Chub [Semotilus atromaculatus] and Blacknose Dace [Rhinichthys atratulus]). Most endemic species persisted in developing reaches, but in lower abundances (e.g., diatoms: Meridion alansmithii Brant; fishes: Mottled Sculpin [Cottus bairdi]). Diatom beta diversity within developing reaches was lower compared to forested reaches, and lower in 2005 and 2010 compared to 2000. Diatom assemblage composition also changed over time in developing reaches but remained stable in forested reaches. In contrast, fish beta diversity showed no significant differences between watershed types or among years, suggesting that diatom assemblages may respond more quickly or to lower levels of watershed development than fish assemblages. We conclude that biotic assemblages in streams draining developing watersheds in southern Appalachia show evidence of homogenization, but not yet extirpation of endemic taxa. Our study demonstrates the importance of understanding the effects of low-density development on biodiversity in stream ecosystems around the world before native species are lost.

Dams are one of the greatest threats to freshwater biodiversity and efforts to remove dams to restore riverine systems are increasing. However, dam-removal studies have primarily focused on taxonomic responses to large dam removals with little work on the functional trait responses of fish to small-dam removals; such a focus limits the application of results in regions with different taxonomic compositions. We explored taxonomic and functional trait responses of fish assemblages to two small-dam removals over 10 years using a Multiple Before After Control Impact design at a dammed and an undammed river. Eight life-history traits were used to calculate functional diversity (RaoQ) and determine the position of each fish species within a multivariate life-history space relative to three life-history strategy endpoints: opportunistic, periodic, and equilibrium. The distance of each species relative to these endpoints was used to calculate community weighted means (CWM), allowing us to examine the shift in life-history strategy of a given assemblage after dam removal. Based on life-history theory, we predicted a decrease in the CWM of equilibrium strategists and an increase in the CWM opportunistic strategists after dam removal. For the dammed river, we observed changes in assemblage structure at both the control and impact sites driven primarily by shifts from a lentic to lotic assemblage, with the most apparent change occurring in the formerly impounded sites. These changes tended to occur within 1 year, suggesting rapid colonization by lotic species after habitat change. By contrast, no change in assemblage structure was found for the undammed river, suggesting that dam removal was the primary driver of the shifts in assemblage structure observed in the dammed river. We found no change in the CWM of periodic strategists or RaoQ of all life-history traits at any site after dam removal. Based on CWM, life-history strategies shifted in response to dam removal at impounded sites where equilibrium strategists decreased and opportunistic strategists tended to increase after the impounded sites changed from a stable lentic environment to an unstable lotic environment, supporting predictions made by life-history theory. Our results suggest that small-dam removal may provide ecological benefits by restoring fish assemblages to a more natural riverine state and reversing the negative effects of dam construction on the ecosystem. We demonstrate that combining both trait-based and taxonomic approaches can improve our ecological understanding of the impacts of dam removal on fish assemblages and provide relevant data for local management.

Introduction Beta diversity represents changes in community composition among locations across a landscape. While the effects of human activities on beta diversity are becoming clearer, few studies have considered human effects on the three dimensions of beta diversity: taxonomic, functional, and phylogenetic. Including anthropogenic factors and multiple dimensions of biodiversity may explain additional variation in stream fish beta diversity, providing new insight into how metacommunities are structured within different spatial delineations. Methods In this study, we used a 350 site stream fish abundance dataset from South Carolina, United States to quantify beta diversity explainable by spatial, natural environmental, and anthropogenic variables. We investigated three spatial delineations: (1) a single whole-state metacommunity delineated by political boundaries, (2) two metacommunities delineated by a natural geomorphic break separating uplands from lowlands, and (3) four metacommunities delineated by natural watershed boundaries. Within each metacommunity we calculated taxonomic, functional, and phylogenetic beta diversity and used variation partitioning to quantify spatial, natural environmental, and anthropogenic contributions to variations in beta diversity. Results We explained 25–81% of the variation in stream fish beta diversity. The importance of these three factors in structuring metacommunities differed among the diversity dimensions, providing complementary perspectives on the processes shaping beta diversity in fish communities. The effect of spatial, natural environmental, and anthropogenic factors varied among the spatial delineations, which indicate conclusions drawn from variation partitioning may depend on the spatial delineation chosen by researchers. Discussion Our study highlights the importance of considering human effects on metacommunity structure, quantifying multiple dimensions of beta diversity, and careful consideration of user-defined metacommunity boundaries in beta diversity analyses.

Black bass Micropterus spp. stocked outside of their native range have often been implicated in declines of native fishes, but impacts of these stockings on native congeners have been examined less commonly and almost never in reservoirs. Relative abundance and creel data were obtained from seven reservoirs (632-13,156 ha) in four southeastern states where Alabama Bass M. henshalli had been illegally stocked. Genetics data for black bass were collected in nine more reservoirs in five southeastern states where similar introductions occurred. In each case, Alabama Bass introduction was swiftly followed by sweeping changes in the black bass composition. Largemouth Bass M. salmoides relative abundance declined by 42-77% after Alabama Bass introduction in four of five reservoirs, but total black bass relative abundance was unchanged in three of them, indicating that Alabama Bass essentially replaced Largemouth Bass. Alabama Bass or their hybrids dominated the black bass genetic sample in five of nine reservoirs, and pure specimens of non-Alabama Bass species composed < 50% of the sample in six of nine reservoirs. Smallmouth Bass M. dolomieu were virtually extirpated via hybridization with Alabama Bass in two of the study reservoirs, and genetically pure fish were rare in several others. These changes occurred over relatively short time intervals, often within 10 years after detection of Alabama Bass, stressing the need for continual vigilance via routine monitoring and a proactive public relations campaign to discourage and limit new introductions. The leading edge of the Alabama Bass invasion now encompasses several notable Smallmouth Bass fisheries in North Carolina and is on the border of numerous others in Tennessee, Virginia, and beyond. The spread of nonnative black bass, such as the Alabama Bass highlighted in this article, constitutes one of the greatest threats to conserving native black bass fisheries.

Objective Habitat alteration is the greatest threat to fishes globally, and freshwater fishes are particularly vulnerable to habitat alteration because freshwater ecosystems are more closely integrated with the human landscape than marine ecosystems. Headwater streams comprise the majority of stream length within a watershed and provide unique habitats for a variety of aquatic organisms, thus contributing to drainage wide species diversity by supporting many rare and endemic species. Unfortunately, because of their small size, headwater streams are particularly susceptible to the effects of habitat alteration and conversion of natural land cover to anthropogenically dominated landscapes. Therefore, understanding fish-habitat relationships is essential for conserving and restoring headwater species and their habitats. The Sandhills Chub Semotilus lumbee is a headwater specialist endemic to the Sandhills ecoregion in North Carolina and South Carolina. It has been extirpated from several locations in South Carolina; thus, quantitative information on abiotic habitat factors is needed to guide conservation and restoration efforts. The objective of this study was to produce a predictive model of Sandhills Chub occurrence using microhabitat features and watershed-level habitat characteristics.Methods Logistic regression was used to identify which habitat features were associated with the occurrence of Sandhills Chub. Habitat and fish data were collected between 2019 and 2020 at 115 sites within the South Carolina Sandhills.Result Sandhills Chub (total = 431) were collected at 41 out of 115 sites sampled. We observed that Sandhills Chub presence was positively associated with dissolved oxygen levels, instream cover, the percent of substrates between 6 and 11 mm, and elevation and was negatively related to the number of impoundments within each 12-digit hydrologic unit code.Conclusion The Sandhills Chub prefers streams that have high dissolved oxygen content, presence of instream cover, the substrates necessary to construct their pit-ridge nests, low numbers of impoundments on the streams, and higher elevations within the Sandhills. Results from this study will provide important information to guide management decisions for the future conservation and restoration of Sandhills Chub.

Charismatic indicator species, which are defined by their sensitivity to ecosystem degradation and attractive traits, are often reintroduced or monitored in restoration projects to evaluate whether desired ecosystem structure and function has been restored and to attract public support for restoration projects. Hymenocallis coronaria is a charismatic and imperiled aquatic plant endemic to southeast U.S. fall line streams. Known for its blooms and sensitivity to flow modification, it provides an opportunity to incorporate the reintroduction of a charismatic indicator species into stream restoration projects. The goal of our research was to provide restoration practitioners with experimentally derived H. coronaria reestablishment best practices by investigating the effects of life stage and outplanting technique on establishment success, with additional considerations given to treatment efficiency. We used binomial generalized linear models to analyze H. coronaria establishment from experimental reestablishment efforts in a free‐flowing segment of Stevens Creek, South Carolina. Model selection showed a strong interaction effect between life stage and outplanting technique and that technique is more important than life stage. Interpretation of our top model indicated that the wedge technique was the most successful and that wedging spring bulbs was significantly more successful than wedging other life stages. However, we recommend that practitioners wedge seedlings or broadcast seeds into existing shoal crevices because of efficiency. Our best practices reflect the need to align reestablishment efforts with H. coronaria 's life history to maximize efficiency and suggest that H. coronaria has utility as an indicator species for restored flow regimes of southeast U.S. fall line streams.

The Atlantic slope region of the southeastern US encompasses a broad geographic area from 38°N to 26°N latitude, ranging from central Virginia to eastern Florida. The southeastern Atlantic slope contains sixteen major rivers. They contain the York River on the northernmost border to rivers on the eastern coast of Florida. There are three freshwater ecoregions within the southeastern Atlantic slope region, divided primarily as a function of latitude and drainage basin. The rivers show great variations in their geomorphology, hydrology, chemistry, and biology. The large rivers originating in the mountains offer the greatest change in aquatic biota because each of them begins as high-gradient systems and end as low-gradient systems, during which they traverse substantially different geological formations and substrata. Although precipitation is relatively uniform throughout the region, natural discharge regimes are strongly seasonal. Rivers of the southeastern Atlantic slope have a high degree of biological distinctiveness. This chapter discusses five major rivers that together cover a considerable range in natural diversity and human impacts: James, Cape Fear, Savannah, Ogeechee, and St. Johns.

In a metacommunity context, beta diversity is driven by the interplay between abiotic factors and dispersal as represented by spatial distance among communities. Most existing studies have considered only ‘natural’ abiotic factors and have ignored anthropogenic factors such as land cover change and pollution. Most studies have focused only on taxonomic beta diversity, and few have considered functional or phylogenetic beta diversity. Including anthropogenic factors and multiple dimensions of biodiversity may explain additional variation in beta diversity, providing new insight into how metacommunities are structured across the landscape. In this study, we used a 350 site stream fish abundance dataset from South Carolina, USA to quantify variation in beta diversity explainable by dispersal, as well as natural and anthropogenic abiotic variables. We investigated metacommunity drivers along three spatial delineations by breaking up the dataset into a metacommunity at the whole state level, two geomorphologically distinct metacommunities of the upstate and lowlands, and four natural watershed metacommunities. Within each of these metacommunities we calculated taxonomic, functional, and phylogenetic beta diversity and used variation partitioning to determine explained variation. We explained 25-81% of beta diversity for stream fish metacommunities. We observed differing importance of spatial, natural, or anthropogenic factors based on the spatial delineation and diversity dimension. We detected distinct structuring of stream fish communities in South Carolina occurring between the upstate and the lowlands. When accounting for the geomorphic differences the fall line creates, we observed a significant anthropogenic signal in the upstate and lowland metacommunities. Spatial, environmental, and anthropogenic factors explained slightly more variation in beta diversity for the taxonomic dimension compared to the functional and phylogenetic dimensions. Our study highlights the importance of including anthropogenic factors when trying to determine mechanisms for stream fish community structure and the significance of spatial delineation in how researchers interpret their results.

Anthropogenic impacts on the landscape can drive biotic homogenization whereby distinct biological communities become more similar to one another over time. Land-use change in the Southern Appalachian region of the United States is expected to result in homogenization of the highly diverse freshwater fish communities as in-stream habitat alterations favor widespread cosmopolitan species at the expense of more narrowly distributed highland endemic species. We compiled four datasets spanning 25 years to (1) evaluate the effects of environmental factors on relative abundance and richness of highland endemic vs. cosmopolitan species in this region and (2) test for taxonomic homogenization, measured as a change in beta diversity over time. We found that several environmental factors differentially affected highland endemic and cosmopolitan species, with the proportion of forested land cover in a watershed most strongly predicting higher relative abundance and richness of highland endemic species. Our analysis of beta diversity change, however, shows mixed evidence of taxonomic homogenization, depending on how common species are weighted. Shifts in community composition, with or without homogenization, may warrant attention in biodiversity conservation planning.

Regional frameworks enable bioassessment methods to detect anthropogenic effects on ecosystems amid natural variability. Conventional approaches to regionalization have used coarse geographical frameworks to separate sites similar in their ecological (ecoregion) or faunal (basin) characteristics. Expectations for individual streams are then adjusted for within-region variability in local environmental characteristics. Integrating regional frameworks and local variability may improve the sensitivity and performance of bioassessments. In this study, we used a biologically-informed stream classification to develop an integrated regional framework for bioassessment considering the effects of ecoregion, basin, and local environmental variables on wadeable stream fish communities of South Carolina, USA. Our integrated framework was compared against conventional regional frameworks indexing ecoregions or basins alone. Frameworks were evaluated by their ability to (1) efficiently partition community variation and (2) allow for the detection of anthropogenic effects on fish communities. We found an integrated framework better described natural variability in stream fish communities. In addition, we found highly regional relationships between fish metrics and anthropogenic disturbance among frameworks, suggesting appropriate bioassessment metrics will differ across regions in our study area. Differences in community response to disturbance among frameworks emphasize the importance of testing metrics for their hypothesized sensitivity before using them in bioassessment. This study ultimately supports the integration of regional frameworks across spatial scales to classify streams for bioassessment, and provides an analytical framework from which to evaluate biotic variation and metric utility in the context of bioassessment.

The natural flow regime (i.e. magnitude, frequency, duration, timing and rate of change of flow events) is crucial for maintaining freshwater biodiversity and ecosystem services. Protecting instream flow from anthropogenic alterations first requires an understanding of the relationship between aquatic organisms and the flow regime. In this study, we used a unique framework based on random forest modeling to quantify effects of natural flow regime metrics on fish and macroinvertebrate assemblages across ecoregions and flow regime types in the state of South Carolina, USA. We found that all components of the natural flow regime affected both fish and benthic macroinvertebrate assemblages, suggesting that maintaining natural aspects of all flow regime components is critical for protecting freshwater diversity. We identified hydrologic metrics and flow regime components such as magnitude, frequency, and duration of flow events, that were associated with the greatest ecological responses for individual stream classes to help managers prioritize hydrologic and biological metrics of interest during environmental flow standard development. The response of aquatic organisms to hydrologic metrics varied across stream classifications and ecoregions, highlighting the importance of accounting for differences in flow regime and ecoregion when designing environmental flow standards. We provide a flexible framework based on statistical flow-ecology relationships that can be used to inform instream flow management and assess effects of flow alteration on riverine assemblages.

"Bartram's Bass" Micropterus sp. cf. coosae is endemic to the upper Savannah River basin of the southeastern United States and is threatened by hybridization with invasive Alabama Bass Micropterus henshalli. Bartram's Bass have been functionally extirpated from reservoirs, and hybrid individuals have been detected in several tributaries. However, the extent of introgression in tributaries is currently unknown. Our objectives were to (1) assess the distribution of Bartram's Bass, native Largemouth Bass M. salmoides, invasive Alabama Bass, and their hybrids in streams of the upper Savannah River basin and (2) quantify effects of abiotic variables on the distribution of each species. We sampled 154 locations in 2017 and 2018 and assigned genetic identity using hydrolysis probes and microsatellites. We used conditional inference trees to quantify variables affecting the occurrence of each species and hybrids. We observed widespread hybridization across the basin. Pure Bartram's Bass were collected at 27% (42) of sites, among which only 12 sites contained pure Bartram's Bass and no other congeners. Thirty sites where pure Bartram's Bass were collected contained hybrids. In the montane Blue Ridge ecoregion, occurrence of pure Bartram's Bass was negatively affected by low levels of local-scale developed land cover. In the lower-relief Piedmont ecoregion, pure Bartram's Bass were positively associated with watershed-scale forest land cover and stream gradient. Distance from a reservoir was positively associated with occurrence of pure Bartram's Bass in both ecoregions. Pure Bartram's Bass are likely to occur with high probability in only 16% of nonimpounded stream segments; this represents a conservative estimate, and the true number is likely lower. However, future work accounting for incomplete detection of Bartram's Bass will help to improve confidence in true extirpations. Conservation efforts may be more successful if implemented on stream segments farther from reservoirs or upstream of dispersal barriers preventing colonization of Alabama Bass.

Stream classification frameworks are important tools for conserving aquatic resources. Yet despite their utility, most classification frameworks have not incorporated network connectivity. We developed and compared three biologically informed stream classification frameworks considering the effects of variables indexing local habitat and/or connectivity on stream fish communities. The first framework classified streams according to local environmental variables largely following the precedent set by previous stream classifications. The second framework classified streams according solely to network connectivity variables, while the third framework considered both local and connectivity variables. Using fish community data from 291 wadeable streams in South Carolina, USA, we used conditional inference tree analyses to identify either seven or eight discrete types of wadeable streams within each framework. Classifications were evaluated on their ability to describe community composition at a subset of sites not used in model training, and canonical correspondence analysis suggested that each framework performed similarly in describing overall community variation, with about 19% of variation explained. After accounting for the effects of biogeography and land use in our analytical approach, each classification explained a substantially higher amount of community variation with 46% of variation explained by our connectivity-informed classification and 42% explained by our locally informed classification. Classifications differed in their ability to describe elements of community structure; a classification incorporating connectivity predicted species richness better than the one that did not. This study ultimately addresses an important knowledge gap in the classification literature while providing broader implications for the conservation of aquatic organisms and their habitats.

Despite being common, low-conductivity (<70 mu S/cm), headwater streams are often understudied compared with larger waters that support recreational and commercial fisheries. However, recent conservation efforts that have focused on native, nongame species have created the need to develop and test sampling methods in these habitats. We compared a novel combination of gears (electrofishing coupled with kick-seining) to three-pass electrofishing for sampling fish assemblages in low-conductivity streams. At each site, each method was used to sample separate reaches equal to 35-fold the mean stream width. We compared CPUE and species richness between the two methods and used logistic regression to estimate the probability of capturing a new species on the second and third passes when electrofishing. We calculated the capture probabilities for the most common species encountered using the Carle-Strub depletion method, with the three-pass electrofishing data. When compared with the combination method, three-pass electrofishing resulted in significantly greater CPUE and species richness (0.21 vs. 0.13 fish/m(2) and 7.24 vs. 5.00 species, respectively). There was a 67% probability of capturing a new species on the second pass and 30% probability of capturing a new species on the third pass when using three-pass electrofishing. The capture probabilities ranged from 0.50 to 0.87 for the 13 species examined. The use of kick-seining after a single electrofishing pass provided no benefit compared with additional electrofishing passes. We recommend making at least three passes while electrofishing when estimating relative abundance and species richness in low-conductivity wadeable streams.

Understanding biodiversity patterns and their drivers across large spatial scales has become a necessary component of addressing complex multiscale conservation challenges. Increasingly, functional diversity measures are being used to provide insight on the ecological integrity of ecosystems. We estimated functional diversity at two different spatial extents using data sets of contrasting sampling intensity and time duration and compared these two different approaches. For our regional-scale analysis, we used large-scale fish sampling data sets and identified 397 species across subbasins within the southeastern USA. For our state-scale analysis, we used data from the South Carolina Department of Natural Resources Statewide Stream Assessment through which 101 species were collected from wadeable streams across South Carolina. For all fish species, we scored trophic and reproductive traits and measured trophic and reproductive functional diversity across subbasins and South Carolina streams. We assessed differences in functional diversity between level III ecoregions, quantified the influence of imperiled and invasive species on functional diversity, and modeled relationships between functional diversity and environmental variables at the state scale using Random Forest regression. At both scales, we found support for higher trophic functional diversity in high-elevation ecoregions, while reproductive functional diversity was generally higher in low-elevation ecoregions. The inclusion of imperiled species increased functional diversity estimates, while invasive species decreased functional diversity estimates except for reproductive functional diversity at the regional scale. Environmental variables that correlated with functional diversity at the state scale included forest cover, elevation, and conductivity. The observed spatial patterns of functional diversity, the environmental variables identified as predictors of functional diversity, and knowledge of how imperiled and invasive species influence functional diversity can be used to guide freshwater fish conservation efforts across the southeastern U.S. region. Additionally, these findings highlight the utility of data from intensive, standardized, broad-scale aquatic surveys in addressing these and similar questions regarding freshwater diversity.