Structure Of Fish Assemblages In Streams Research Articles

The influence of landscape at multiple spatial scales of the river basins at the Eastern Amazon fish assemblage

Abstract The Amazon River basins present distinct natural and anthropogenic characteristics that influence the structure of stream habitats and their associated biota. The influence of these characteristics can be evaluated through different spatial scales. We aimed to assess the influence (with and without the effect of spatial-geographical factors) of local, macroscale, and land-use variables in the structure of stream fish assemblages of Amazonian catchments with different deforestation levels. A partial redundancy analysis and a reduced metrics model were used to assess these influences. With geographic-spatial effects, we verified that the macroscale and local variables explained the variation in fish composition, and, without the effects, land use also explained the variation in this composition. In the forested catchments, the biota was associated with streams with natural characteristics (e.g., leaf banks). In the deforested catchments, it was associated with land use, sandy catchments with higher soil density (higher capacity of degradation), and less complex streams (fewer leaf banks, more sand). The associated fish have life features linked to these characteristics (e.g., Gymnorhamphichthys rondoni associated with sand). This configuration seems to be a result of both the impact of land use in the catchment (i.e., increased erosion, increased sedimentation) and the naturally sandy constitution of the catchment as well, reflecting the sandy substrate.

Hydrologic and environmental thresholds in stream fish assemblage structure across flow regimes

The characteristic pattern of variation in flow magnitude, frequency, duration, timing, and rate of change defines the flow regime of rivers and streams and is a key driver of ecosystem processes in fluvial ecosystems. Understanding how freshwater biotic assemblages change across gradients of hydrology and anthropogenic-source disturbance in different streamflow regimes is crucial to managing for sustainable environmental flows and watershed conservation. We compiled long-term (1916–2016) occurrence records for fishes collected in the Ouachita-Ozark Interior Highlands and West Gulf Coastal Plain streams, together with hydrologic metrics calculated from daily streamflow data measured at USGS stream gauging stations (n = 111), to examine important drivers and thresholds for fish assemblage turnover in groundwater (GW), runoff (RO), and intermittent (INT) flow regimes. We also examined the importance of spatial gradients (latitude, longitude, elevation, drainage area) and anthropogenic-source stressors (Hydrologic Disturbance Index; HDI) for fish assemblage turnover using a gradient forest modeling approach. Watershed fragmentation was of high importance for fish assemblage turnover in RO and INT streams, while changes in dam storage were more important for fishes in GW streams. Hydrologic metrics describing seasonal and stochastic properties of daily streamflow (Mag6) were most important for fish assemblage turnover in INT streams. Timing of high flow events had significantly higher importance compared to flow magnitude, duration, and frequency metrics, especially for fish assemblages in GW and INT streams. The frequency and timing of low flow events had high importance for fish assemblage turnover across all stream flow classes, while the magnitude of low flows and the magnitude and rate of change of average flows was most important for INT stream fish assemblages. In addition to benefiting multi-species conservation and management actions through identification of local and regional flow-ecology relationships generalized across different flow regimes, the results of this study provide a better understanding of complex nonlinear threshold effects, which is critical to anticipating changes in aquatic ecosystems and communities.

Correction to: The effect of different logging regimes on the ecomorphological structure of stream fish assemblages in the Brazilian Amazon

Correction to: The effect of different logging regimes on the ecomorphological structure of stream fish assemblages in the Brazilian Amazon

The effect of different logging regimes on the ecomorphological structure of stream fish assemblages in the Brazilian Amazon

AbstractWe evaluated the effects of changes in habitat structure resulting from conventional logging (CL) and reduced-impact logging (RIL) on the ecomorphological structure of stream fish assemblages in the eastern Brazilian Amazon, investigating (1) which habitat characteristics are influenced by different logging methods, (2) the differences in the ecomorphological structure of fish assemblages between two logging methods and undisturbed forest (UF), and (3) the relationships between ecomorphological traits of fish assemblages and habitat variables. We measured 13 habitat variables and characterized 11 ecomorphological traits of 55 fish species collected in 34 sampling sites (stream stretches) located in CL, RIL, and UF. In logged areas, the streams present a fine sediment increase and reduced vegetation cover, while in the UF a greater amount of natural shelter and more cover vegetation were observed. These environmental changes selected ecomorphological traits of stream fish assemblages, recording a greater relative width of the mouth in UF, higher ventral flattening index in RIL, or greater relative head length, and higher caudal peduncle compression index in CL. In this sense, we recommend that logging practices, including RIL, should be reviewed as a means of adopting better strategies to minimize human disturbances in streams.

Land-use changes affect the functional structure of stream fish assemblages in the Brazilian Savanna

Abstract We investigated the mechanisms involved in the relationship between land-use changes and aquatic biodiversity, using stream fish assemblages of the Brazilian Savanna (i.e., Cerrado) as a study model. We tested the prediction that landscape degradation would decrease environmental heterogeneity and change predominant physical-habitat types, which in turn would decrease the functional diversity and alter the functional identity of fish assemblages. We sampled fish from 40 streams in the Upper Paraná River basin, and assessed catchment and instream conditions. We then conducted an ecomorphological analysis to functionally characterize all species (36) and quantify different facets of the functional structure of assemblages. We detected multiple pathways of the impacts from landscape changes on the fish assemblages. Catchment degradation reduced the stream-bed complexity and the heterogeneity of canopy shading, decreasing assemblage functional specialization and divergence. Landscape changes also reduced the water volume and the amount of large rocks in streams, resulting in decreased abundances of species with large bodies and with morphological traits that favor swimming in the water column. We conclude that land-use intensification caused significant changes in aquatic biodiversity in the Cerrado, reinforcing the need to pay special attention to this global hotspot.

Do body mass and habitat factors predict trophic position in temperate stream fishes?

In animals with indeterminate growth, such as predatory fishes, mouth size is related to, and increases with, body mass of the organism. As fishes grow in body size, they can consume larger-bodied prey items at potentially-higher trophic levels. Therefore, body size should predict trophic position. Trophic position (TP) is useful for describing energy flow between biota, giving a more comprehensive picture of aquatic food webs, but the factors that influence the body-size–TP relationship are unclear. Additionally, stable isotope-derived TP and body-size relationships are untested for temperate freshwater fishes. Using linear mixed-effects models, we tested fish body mass as a predictor of TP across 6 species of temperate freshwater fish (n = 921 total individuals) sampled from 110 stream reaches in New Zealand, and we evaluated habitat factors (flood disturbance and stream size) likely to affect trophic structure of stream fish assemblages. Supporting ecological theory, but contrasting with some previous findings in marine and tropical environments, we found that TP was positively associated with body size across all species. Habitat factors did not affect fish TP. However, stream network spatial factors included in models as random effects explained the majority of variance in TP across species. Thus, while our study shows that New Zealand temperate freshwater fish body size is positively associated with stable isotope-derived TP, researchers will need to account for catchment-specific spatial factors to make accurate inferences about TP based on body size.

Intercontinental trends in functional and phylogenetic structure of stream fish assemblages.

Understanding of community assembly has been improved by phylogenetic and trait‐based approaches, yet there is little consensus regarding the relative importance of alternative mechanisms and few studies have been done at large geographic and phylogenetic scales. Here, we use phylogenetic and trait dispersion approaches to determine the relative contribution of limiting similarity and environmental filtering to community assembly of stream fishes at an intercontinental scale. We sampled stream fishes from five zoogeographic regions. Analysis of traits associated with habitat use, feeding, or both resulted in more occurrences of trait underdispersion than overdispersion regardless of spatial scale or species pool. Our results suggest that environmental filtering and, to a lesser extent, species interactions were important mechanisms of community assembly for fishes inhabiting small, low‐gradient streams in all five regions. However, a large proportion of the trait dispersion values were no different from random. This suggests that stochastic factors or opposing assembly mechanisms also influenced stream fish assemblages and their trait dispersion patterns. Local assemblages tended to have lower functional diversity in microhabitats with high water velocity, shallow water depth, and homogeneous substrates lacking structural complexity, lending support for the stress‐dominance hypothesis. A high prevalence of functional underdispersion coupled with phylogenetic underdispersion could reflect phylogenetic niche conservatism and/or stabilizing selection. These findings imply that environmental filtering of stream fish assemblages is not only deterministic, but also influences assemblage structure in a fairly consistent manner worldwide.

Effects of pasture conversion to sugarcane for biofuel production on stream fish assemblages in tropical agroecosystems

Abstract One of the main causes of biodiversity loss in aquatic ecosystems is instream habitat change associated with land‐use change in the drainage basin. Biofuel crop production is an increasingly important driver of land‐use change in existing agricultural drainage basins. Conceptually, biofuels such as sugarcane (Saccharum spp.: Poaceea) can provide a sustainable alternative to fossil fuels, but little is known about the consequences of biofuel crop production for biodiversity. Thus, our aim was to investigate if and how the degree of further environmental changes at regional and local scales can influence taxonomic and functional structure of fish assemblages in agroecosystem streams. We quantified drainage basin land use, instream and riparian habitat, and fish assemblages in 38 agroecosystem streams in Brazil with drainage basins experiencing rapid expansion of sugarcane production, and calculated degree of environmental change and corresponding response in taxonomic and functional structure of stream fish assemblages. Procrustes and redundancy analyses tested for correlation between land use and instream habitat and environmental factors correlated with fish assemblage structure, respectively. Previous studies demonstrated relationships between land‐use change, instream habitat change and taxonomic and functional structure of stream fish assemblages. Therefore, we used regression to test the hypothesis that degree of environmental change is positively correlated with magnitude of change in taxonomic and functional structure of fish assemblages. Primary gradients of environmental change included conversion of pasture to sugarcane and reduction of stream width, depth and volume. Although drainage basin and instream attributes were not correlated within a year, we detected a legacy effect of land use on instream habitat. The degree of environmental change was not significantly correlated with taxonomic or functional changes in stream fish assemblages in most cases. However, abundances of resistant taxa increased, whereas nektonic functional groups decreased, and the biological response also presented evidence of a legacy effect. Our findings demonstrate that instream habitat and aquatic biodiversity in streams with agricultural drainage basins undergoing rapid conversion to biofuel production likely will not experience the full magnitude of responses in the short term. Therefore, repeated sampling of sufficient duration to account for legacy effects or time lags is needed to test for effects of biofuel expansion on biodiversity, and similarly to assess whether management practices such as riparian zone preservation can benefit biodiversity in agroecosystems.

Headwater captures and the phylogenetic structure of freshwater fish assemblages: a case study in central Brazil

Aim The astonishing diversity of Neotropical fishes results from historical and ecological processes intrinsically related to the geomorphological evolution of this region. Headwater captures are important biogeographical processes that promote dispersal or isolation of fish populations between watersheds. We investigate the effects of headwater captures on the phylogenetic structure of stream fish assemblages among watersheds in the Brazilian Shield highlands. Location Headwaters of Tocantins, Parana and Sao Francisco watersheds, Brazilian Shield, Neotropical region. Methods Based on the phylogenetic relationships of 70 native fish species, we quantified the phylogenetic diversity of each basin, as well as species richness and the phylogenetic beta diversity between basins. Results The Upper Parana basin showed higher richness and phylogenetic diversity, indicating phylogenetically distant species composition. The number of shared species and phylogenetic beta diversity values were not different from the null expectation, indicating recent exchange of species between the basins. Main conclusions Our results suggest that the fish assemblage of the Upper Parana basin is older and many species colonized recently the neighbouring Upper Tocantins and Sao Francisco basins, highlighting the impact of headwater captures on the community assembly of Neotropical fishes.

Taxonomic and functional organization in metacommunity structure of stream-fish assemblages among and within river basins in Texas

Metacommunities are spatially structured communities linked by dispersal. They provide a connection between local community assembly and regional-level processes. One of the more widely used methods to address questions related to metacommunity concepts is those that characterize elements of metacommunity structure by quantifying aspects of coherence, species turnover, and boundary clumping. In this study, we used this approach to study the spatial ecology of freshwater fishes in Texas. Stream-fish assemblages in Texas provide an excellent opportunity to examine the patterns of metacommunity structure due to the number of drainages that empty directly into the Gulf of Mexico, which minimizes the likelihood of dispersal between basins while allowing for longitudinal movement within basins. We used fisheries data published by the Texas Parks and Wildlife Department and from the North American Water Quality Association, which consisted of 94 sampling localities distributed across 18 river basins and 11 ecoregions. To examine within-basin patterns, we focused only on the Brazos, Colorado, and Trinity rivers because of the number of sites within each of these basins. From a taxonomic standpoint, we consistently observed Clementsian patterns regardless of whether it was among or within river basins, whereas we mostly observed Gleasonian patterns from a functional perspective. Only one functional group was found at all sites in each of the three main river basins, which consisted of invertivores with an equilibrium life-history strategy. Various bioclimatic variables were significantly correlated with metacommunity structure, but these correlations differed between taxonomic and functional organization and differed depending on which river basin was considered. The results of this study support previous findings that species composition and functional traits relate to environmental gradients, but further our understanding by providing additional evidence that species sorting processes are the dominant structuring mechanisms.

Evaluating habitat associations of a fish assemblage at multiple spatial scales in a minimally disturbed stream using low‐cost remote sensing

Abstract Habitat heterogeneity at multiple scales is a major factor affecting fish assemblage structure. However, assessments that examine these relationships at multiple scales concurrently are lacking. The lack of assessments at these scales is a critical gap in understanding as conservation and restoration efforts typically work at these levels. A combination of low‐cost side‐scan sonar surveys, aerial imagery using an unmanned aerial vehicle, and fish collections were used to evaluate the relationship between physicochemical and landscape variables at various spatial scales (e.g. micro‐mesohabitat, mesohabitat, channel unit, stream reach) and stream–fish assemblage structure and habitat associations in the South Llano River, a spring‐fed second‐order stream on the Edwards Plateau in central Texas during 2012–2013. Low‐cost side‐scan sonar surveys have not typically been used to generate data for riverscape assessments of assemblage structure, thus the secondary objective was to assess the efficacy of this approach. The finest spatial scale (micro‐mesohabitat) and the intermediate scale (channel unit) had the greatest explanatory power for variation in fish assemblage structure. Many of the fish endemic to the Edwards Plateau showed similar associations with physicochemical and landscape variables suggesting that conservation and restoration actions targeting a single endemic species may provide benefits to a large proportion of the endemic species in this system. Low‐cost side‐scan sonar proved to be a cost‐effective means of acquiring information on the habitat availability of the entire river length and allowed the assessment of how a full suite of riverscape‐level variables influenced local fish assemblage structure. Copyright © 2015 John Wiley & Sons, Ltd.

Ecoregional, catchment, and reach-scale environmental factors shape functional-trait structure of stream fish assemblages

Patterns of association between functional traits and environmental gradients can improve understanding of species assemblage structure from local to regional scales, and therefore may be useful for natural resource management. We measured functional traits related to trophic ecology, habitat use, and life-history strategies of fishes and examined their associations with environmental factors in the Brazos and Trinity River basins in Central Texas. We also examined the relationship between functional diversity of fish assemblages and indices of biotic integrity and habitat quality. Environmental characteristics at the local reach and catchment scales, including the extent of forested area in the watershed, amount of land developed for urban and agricultural uses, stream size, substrate characteristics, and availability of riffle and pool habitats, were significantly associated with functional trait composition of fish assemblages. Broad physiographic differences between ecoregions also had a large influence on taxonomic and functional assemblage structure. In general, the volume of functional trait space occupied by fish assemblages was greatest in streams with high habitat quality scores located within landscapes having less alteration from agriculture and urban development. Distributions of functional traits in fish assemblages might provide an additional basis for assessment of stream condition in relation to environmental impacts.

Contribution of environmental and spatial factors to the structure of stream fish assemblages at different spatial scales

AbstractTo compare the contributions of environmental and spatial factors in structuring assemblages of temperate stream fish on different spatial scales, I evaluated the distance decay of fish assemblage similarity and correlations among species compositions, environmental factors and geographical locations at medium (inter‐reach scale, spatial extent 40 km) and fine (inter‐microhabitat scale, spatial extent <200 m) scales. Partial redundancy analysis and variation partitioning indicated that the ordinal rank of the relative importance of environmental and spatial factors differed among scales. At the medium scale, the distance decay of similarity of species composition was steep at approximately >10‐km scale, and the assemblage structure was simply explained by the distance between sites and several environmental factors (e.g., elevation and current velocity). In contrast, the distance between microhabitats explained only a small portion of the variance in species composition at the fine scale, and fish assemblages were affected by several spatial patterns of habitat (or some environmental features associated with those spatial patterns). Environmental factors at the fine scale (e.g., substratum characteristics and presence/absence of cover) correlated with each other and were spatially structured, and their contribution to species variance was smaller than that at the medium scale. These results provide evidence for scale‐dependent alternation of the rank of the relative importance of environmental and spatial factors in structuring assemblages of stream fishes via the turnover of crucially contributing factors from medium to fine spatial scales.

Patterns in Stream Fish Assemblage Structure and Function Associated With a PCB Gradient

Stream fish assemblage structure and function were examined for significant response along a polychlorinated biphenyl (PCB) gradient from two PCB-contaminated streams (Clear Creek and Richland Creek watershed) at three locations and a control stream (Little Indian Creek), Indiana, USA. Fish were sampled in the summer months of 1995 and from 1999 to 2002. 51 fish assemblage attributes-including structure (i.e., fish composition) and function (i.e., trophic, reproductive, condition guilds), biomass, and index of biotic integrity (IBI) metric scores-were evaluated for significance according to an increasing PCB gradient. Eight biomass attributes of fish assemblages decreased with increasing PCB concentration: number of species biomass, number of sunfish biomass, percent sunfish biomass, number of sucker biomass, percent sucker biomass, biomass of sensitive species, percent sensitive species biomass, and percent carnivore biomass. Three biomass attributes increased with PCB concentration: percent minnow biomass, percent pioneer species biomass, and percent tolerant species biomass. Seven species composition and relative abundance characters decreased with increasing PCB concentration: number of species; number of darter, madtom, and sculpin; number of darter; number of sunfish; number of sucker; number of sensitive species; and percent individuals as carnivores. Percent individuals as pioneer species increased with increasing PCB concentration. Two IBI metrics, percent individuals as headwater species and number of minnow species, increased as PCB concentrations increased, whereas number of sucker species and percent individuals as pioneer species decreased with increasing PCB concentration class. We observed a direct response between decreased relative abundance and biomass of carnivores and increased relative abundance minnows as the PCB gradient increased. Total IBI score did not detect subtle changes to the fish community that were observed along a PCB gradient, whereas diagnostic analysis of the individual metrics did.

Effects of local and regional factors on the fish assemblage structure in Meridional Amazonian streams

The aim of this study was to evaluate the effects of local, regional and temporal factors structuring fish assemblages in Meridional Amazonian streams during the months of May (rainy season) and August (dry season) of 2008. To accomplish this task, 14 streams located in Serra do Expedito (Aripuana River basin) were sampled along 30-m stretches. A total of 3,212 specimens distributed among five orders, 18 families, and 55 species were recorded. The fish assemblage structure in the streams presented variation among types of riparian vegetation (local factor) and watersheds (regional factor), but did not present variation between seasons (temporal factor) and stream order (regional factor). Larger streams with margins covered with pasture presented higher species richness and abundance than smaller streams with margins covered with forest.

Fish assemblage structure in urban streams of Puerto Rico: the importance of reach- and catchment-scale abiotic factors

Channelization and urbanization are anthropogenic alterations that act on the reach- and catchment-scale, respectively, to degrade stream habitats. As urban areas continue to expand in the tropics the number of channelized streams will likely increase as well. We examined in-stream habitat and fish assemblage structure in stream reaches with a range of channel alterations and sub-catchment urban land use in the Rio Piedras watershed, Puerto Rico. Nine reaches were surveyed and classified into three categories: unaltered channels (natural), channels that had been straightened and may have reinforced banks (intermediate), or channels where the bank and bottom was replaced with concrete (concrete-channelized). Fishes were sampled using triple-pass electrofishing and relevant reach- and catchment-scale abiotic environmental variables were measured for each site. Fish assemblage structure in the Rio Piedras appears to be influenced by both reach- and catchment-scale abiotic environmental factors. Natural and intermediate reaches with moderately high levels of sub-catchment urbanization had relatively high biomass, species-rich, and native-dominated fish assemblages whereas concrete-channelized reaches with very highly urbanized sub-catchments had fish assemblages with few to no native species and highly abundant, tolerant, and exotic species.

A GIS approach for explanation of fish assemblage structure in a large river

Although using Geographic Information Systems (GIS) has become common in ecology, few river stud- ies incorporate this technology into examining habitat variables and use of habitat by individual fishes. Our goal was to demonstrate these GIS techniques and to test for the ability to predict fish and habitat relationships using the same data in a multivariate analysis. We collected channel bathymetry, water velocity, and streambed composition using an Acoustic Doppler Current Profiler (ADCP) deployed from a USGS boat and interfaced with a Differential Global Positioning System (DGPS) receiver, for a 10-km study reach of the Wabash River. Individual fishes were collected the following week and assigned spatial coordinates for latitude and longitude. We tested for the ability of a multi- variate technique to explain fish assemblage variation using environmental variables collected in a GIS context. We tested at which of three resolutions the environmental variables explained the highest proportion of fish assemblage variation. For this 10-km reach of the Wabash River, fish assemblages were best explained at a 10 by 10 m resolution with water velocity, water depth, river location, woody debris, and substrate composition. At a lower resolution (30 by 30 m) the same habitat variables provided similar but lower explanation of variation. However, at the highest resolution of 4 by 4 m, environmental variables provided relatively little explanation of fish assemblage structure. We suggest and recommend additional applications of a GIS approach to test temporal and spatial hypotheses of stream fish assemblage structure.

Local and ecoregion effects on fish assemblage structure in tributaries of the Rio Paraíba do Sul, Brazil

Summary1. We examined the effects of physical and chemical habitat variables and ecoregions on species occurrence and fish assemblage structure in streams of the Paraíba do Sul basin, in southeast Brazil.2. Fish and environmental data were collected from 42 sites on 26 first to fourth order streams (1 : 50 000 map scale) in three ecoregions. The sites occurred in one valley and two plateau ecoregions at altitudes of 40–1080 m and distances of 0.1–188 km from the main channel of the Rio Paraíba do Sul. Physical habitat (substratum, riparian cover, habitat types) and water quality (dissolved oxygen, pH, temperature and conductivity) variables were measured at each sampling site.3. A total of 2684 individuals in 16 families and 59 species were recorded.4. Ecoregion was a better predictor of the fish assemblage than the other environmental variables, according to the differences between the mean within‐class and mean between‐class similarities in assemblage data.5. Differing landscape characteristics were associated with differing local variables and thereby with differing fish assemblage structures. Riffles, shrub, grass, dissolved oxygen, conductivity and temperature were closely related to fish assemblage structure.6. Fish assemblages in sites far from the main river and at higher altitudes also differed from those near the Paraíba do Sul main channel, presumably as a result of differences in connectivity, covarying environmental factors and anthropogenic influence.7. These results reinforce the importance of understanding how stream communities are influenced by processes and patterns operating at local and regional scales, which will aid water resource managers to target those factors in their management and rehabilitation efforts.

Effects of land use on fish assemblages in Patagonian low order streams

We assessed the effects of land use on the structure of stream fish assemblages in Northwest Patagonia, Argentina. To this end, a total of 18 sites distributed in 15 streams were sampled during the low water period. At each site, 26 regional and local scale variables were used to describe the environmental conditions. The macroinvertebrate density, and the composition and abundance of fish were then recorded. Statistical associations between local assemblage structures and environmental variables were quantified by canonical correspondence analyses. The results revealed that, at a regional scale, the fish assemblages were primarily determined by watershed features like altitude and catchment area, and by land use effects (exotic forest and pasture). Assemblage compositions were also related to some local-scale features such as water velocity, food availability (density of benthic macroinvertebrates), instream characteristic and riparian features. Also, the observed fish species richness was low. Overall, exotic salmonids largely dominated in the samples both in numbers of individuals (98.9%) and in biomass (99.9%), whereas native fish (Hatcheria macraei and Odontesthes hatcheri ) were scarcely represented. Rainbow trout (Oncorhynchus mykiss ) was the most abundant fish, and was present in all streams. Native species were restricted to five streams located in the ecotone between the Andes and the steppe, where salmonids were also present. Salmonids were the only fish at Andean streams which suggest the existence of a strong geographic segregation between native and exotic species. Some aspects related to the incidence of the introduced species in the structure of fish assemblages are discussed.

Cumulative Industrial Activity Alters Lotic Fish Assemblages in Two Boreal Forest Watersheds of Alberta, Canada

We evaluated the cumulative effects of land use disturbance resulting from forest harvesting, and exploration and extraction of oil and gas resources on the occurrence and structure of stream fish assemblages in the Kakwa and Simonette watersheds in Alberta, Canada. Logistic regression models showed that the occurrence of numerically dominant species in both watersheds was related to two metrics defining industrial activity (i.e., percent disturbance and road density), in addition to stream wetted width, elevation, reach slope, and percent fines. Occurrences of bull trout, slimy sculpin, and white sucker were negatively related to percent disturbance and that of Arctic grayling, and mountain whitefish were positively related to percent disturbance and road density. Assessments of individual sites showed that 76% of the 74 and 46 test sites in the Kakwa and Simonette watersheds were possibly impaired or impaired. Impaired sites in the Kakwa Watershed supported lower densities of bull trout, mountain whitefish, and rainbow trout, but higher densities of Arctic grayling compared to appropriate reference sites. Impaired sites in the Simonette Watershed supported lower densities of bull trout, but higher densities of lake chub compared to reference sites. Our data suggest that current levels of land use disturbance alters the occurrence and structure of stream fish assemblages.