Several hypotheses from community ecology were tested using habitat and diet patterns for six catostomid fishes of the Assiniboine River, Manitoba. Specifically, I examined expected assemblage patterns based on the equilibrium-nonequilibrium continuum that are based on competition as a structuring mechanism. The catostomid assemblage showed characteristics of both equilibrium and nonequilibrium assemblages. Habitat utilization was not proportional to habitat availability for depth, velocity, and substrate indicating habitat selection occurs. These patterns are influenced by the distributions of soft Lake Agassiz deposits and harder glacial till-plain habitats and therefore localized. Species co-occurred in relation to abundance indicating negative associations assumed in competition-based theory were not apparent. In addition, species from the same subfamily co-occurred more often than expected by chance, indicating positive within-group comparisons, except for silver redhorse, which did not co-occur differently than random. Species from the same feeding group co-occur most frequently with conspecifics, indicating species have specific habitat patterns. Benthic invertebrate distributions and fish distributions were positively correlated with fish diet. Within-feeding-group comparisons indicated species that co-occurred frequently consumed the same food items, but showed subtle differences in abundance of diet items. The most common diet items varied among white sucker, silver redhorse, golden redhorse, and shorthead redhorse, indicating that, although these species co-occur, subtle differences in feeding behavior may account for differences in relative abundance and frequency of diet items. Quillback and bigmouth buffalo shared a few core food items, but co-occurred infrequently. Inter-specific interactions showed silver redhorse diets were a subset of white sucker diets, white sucker diets were a subset of golden redhorse diets, shorthead redhorse diets were a subset of silver redhorse and golden redhorse diets, while bigmouth buffalo diets were a subset of quillback diets. Lower richness and prevalence of organisms in quillback and bigmouth buffalo diets were due to highly aggregated prey items. Benthic invertebrate distributions were aggregated and dependent on the predictable patterns of substrates, based on hydraulic sorting in the meandering along the river. Large-scale redundancy of species-habitat associations was correlated with historical (phylogenetic) or adaptive (morphological) constraints on habitat selection. Stream habitats are constrained by regional factors of slope and sediments, but also determined by stable, repetitive and predictable local processes of erosion, transport, and deposition (meandering). The fish-habitat associations of catostomids in the Assiniboine River provide an example of interaction between the abundance of the component species, the phylogenetic constraints on the niche, and the deterministic nature of the spatial distribution of habitats. Within-feeding-group pairs showed that local habitat overlap is positively correlated with geographic overlap, while local diet overlap is negatively correlated with geographic overlap. Two species pairs (silver redhorse and golden redhorse and bigmouth buffalo and quillback) were concluded to have symmetric overlaps at the geographic scale and stable interactions. Using the functional niche concept ecological theory provides a link between ecology and biogeography of sympatric species. The multi-analytical approaches in this study provide insights into the structuring of north temperate prairie river fish communities, through hypothesis testing and correlation that have application beyond Prairie Rivers. / October 2005

Several hypotheses from community ecology were tested using habitat and diet patterns for six catostomid fishes of the Assiniboine River, Manitoba. Specifically, I examined expected assemblage patterns based on the equilibrium-nonequilibrium continuum that are based on competition as a structuring mechanism. The catostomid assemblage showed characteristics of both equilibrium and nonequilibrium assemblages. Habitat utilization was not proportional to habitat availability for depth, velocity, and substrate indicating habitat selection occurs. These patterns are influenced by the distributions of soft Lake Agassiz deposits and harder glacial till-plain habitats and therefore localized. Species co-occurred in relation to abundance indicating negative associations assumed in competition-based theory were not apparent. In addition, species from the same subfamily co-occurred more often than expected by chance, indicating positive within-group comparisons, except for silver redhorse, which did not co-occur differently than random. Species from the same feeding group co-occur most frequently with conspecifics, indicating species have specific habitat patterns. Benthic invertebrate distributions and fish distributions were positively correlated with fish diet. Within-feeding-group comparisons indicated species that co-occurred frequently consumed the same food items, but showed subtle differences in abundance of diet items. The most common diet items varied among white sucker, silver redhorse, golden redhorse, and shorthead redhorse, indicating that, although these species co-occur, subtle differences in feeding behavior may account for differences in relative abundance and frequency of diet items. Quillback and bigmouth buffalo shared a few core food items, but co-occurred infrequently. Inter-specific interactions showed silver redhorse diets were a subset of white sucker diets, white sucker diets were a subset of golden redhorse diets, shorthead redhorse diets were a subset of silver redhorse and golden redhorse diets, while bigmouth buffalo diets were a subset of quillback diets. Lower richness and prevalence of organisms in quillback and bigmouth buffalo diets were due to highly aggregated prey items. Benthic invertebrate distributions were aggregated and dependent on the predictable patterns of substrates, based on hydraulic sorting in the meandering along the river. Large-scale redundancy of species-habitat associations was correlated with historical (phylogenetic) or adaptive (morphological) constraints on habitat selection. Stream habitats are constrained by regional factors of slope and sediments, but also determined by stable, repetitive and predictable local processes of erosion, transport, and deposition (meandering). The fish-habitat associations of catostomids in the Assiniboine River provide an example of interaction between the abundance of the component species, the phylogenetic constraints on the niche, and the deterministic nature of the spatial distribution of habitats. Within-feeding-group pairs showed that local habitat overlap is positively correlated with geographic overlap, while local diet overlap is negatively correlated with geographic overlap. Two species pairs (silver redhorse and golden redhorse and bigmouth buffalo and quillback) were concluded to have symmetric overlaps at the geographic scale and stable interactions. Using the functional niche concept ecological theory provides a link between ecology and biogeography of sympatric species. The multi-analytical approaches in this study provide insights into the structuring of north temperate prairie river fish communities, through hypothesis testing and correlation that have application beyond Prairie Rivers.

Several hypotheses from community ecology were tested using habitat and diet patterns for six catostomid fishes of the Assiniboine River, Manitoba. Specifically, I examined expected assemblage patterns based on the equilibrium-nonequilibrium continuum that are based on competition as a structuring mechanism. The catostomid assemblage showed characteristics of both equilibrium and nonequilibrium assemblages. Habitat utilization was not proportional to habitat availability for depth, velocity, and substrate indicating habitat selection occurs. These patterns are influenced by the distributions of soft Lake Agassiz deposits and harder glacial till-plain habitats and therefore localized. Species co-occurred in relation to abundance indicating negative associations assumed in competition-based theory were not apparent. In addition, species from the same subfamily co-occurred more often than expected by chance, indicating positive within-group comparisons, except for silver redhorse, which did not co-occur differently than random. Species from the same feeding group co-occur most frequently with conspecifics, indicating species have specific habitat patterns. Benthic invertebrate distributions and fish distributions were positively correlated with fish diet. Within-feeding-group comparisons indicated species that co-occurred frequently consumed the same food items, but showed subtle differences in abundance of diet items. The most common diet items varied among white sucker, silver redhorse, golden redhorse, and shorthead redhorse, indicating that, although these species co-occur, subtle differences in feeding behavior may account for differences in relative abundance and frequency of diet items. Quillback and bigmouth buffalo shared a few core food items, but co-occurred infrequently. Inter-specific interactions showed silver redhorse diets were a subset of white sucker diets, white sucker diets were a subset of golden redhorse diets, shorthead redhorse diets were a subset of silver redhorse and golden redhorse diets, while bigmouth buffalo diets were a subset of quillback diets. Lower richness and prevalence of organisms in quillback and bigmouth buffalo diets were due to highly aggregated prey items. Benthic invertebrate distributions were aggregated and dependent on the predictable patterns of substrates, based on hydraulic sorting in the meandering along the river. Large-scale redundancy of species-habitat associations was correlated with historical (phylogenetic) or adaptive (morphological) constraints on habitat selection. Stream habitats are constrained by regional factors of slope and sediments, but also determined by stable, repetitive and predictable local processes of erosion, transport, and deposition (meandering). The fish-habitat associations of catostomids in the Assiniboine River provide an example of interaction between the abundance of the component species, the phylogenetic constraints on the niche, and the deterministic nature of the spatial distribution of habitats. Within-feeding-group pairs showed that local habitat overlap is positively correlated with geographic overlap, while local diet overlap is negatively correlated with geographic overlap. Two species pairs (silver redhorse and golden redhorse and bigmouth buffalo and quillback) were concluded to have symmetric overlaps at the geographic scale and stable interactions. Using the functional niche concept ecological theory provides a link between ecology and biogeography of sympatric species. The multi-analytical approaches in this study provide insights into the structuring of north temperate prairie river fish communities, through hypothesis testing and correlation that have application beyond Prairie Rivers.

The hills of Yazoo Basin have a long history of land use modification and subsequent erosion and flood control issues. In response, federal actions were taken to address these issues beginning after the Mississippi River flood of 1927. Four major flood control reservoirs were built in 1932-1957, and instream low-drop grade control structures (GCS) were installed beginning in the 1980s. The objective of my dissertation was to ascertain the long-term effects of these efforts on stream fish assemblages and channel morphology. To assess whether the reservoirs affected upstream fish assemblages as barriers to recolonization by fluvial fishes or as source population for invasion by lentic generalist fishes (Chapter 1), I used stream data collected 43-61 years after the rivers were impounded to test for differences in fish assemblages between sites upstream and downstream of the reservoirs. Analysis of catch per effort and diversity metrics displayed little influence of the reservoirs, but trait-based analysis revealed marginal increases in planktivores, herbivores, detritivores, and generalists in upstream assemblages. After determining that potential effects of reservoirs would not confound further analysis, I assessed the effects of GCS on channel morphology (Chapter 2) and fish assemblages (Chapter 3) 30 years post-installation. To assess GCS effects on channel morphology, stream cross-sections were used to calculate Bank Height Ratio, Width/Depth Ratio, and Entrenchment Ratio, while point estimates made along the transects were used to calculate the average sediment size distribution. Analyses revealed that the GCS were successful in checking channel incision moving headward in the streams: sites upstream of the GCS were less incised and had greater accumulations of fine substrates compared to downstream sites and sites on streams lacking erosion control structures. The GCS could potentially affect fish assemblages through habitat modification or by selectively filtering the assemblages as a barrier to upstream migration. Analysis of beta diversity revealed that diversity was driven by species replacement rather than nestedness, which indicates GCS were not acting as filters on the assemblages. Analysis of catch per effort data confirmed differences in assemblage structure that echoed the instream habitat differences revealed in Chapter 2.

Stream fishes are highly diverse, yet highly imperiled by human alterations of stream environments. Many species are poorly characterized with regard to the size and structure of populations and patterns of dispersal between populations, which complicates assessment of how human activities, both harmful and beneficial, will affect persistence. I used genetic tools to further this understanding in three case-study fish species of the southeastern United States: Roanoke logperch (Percina rex) of the greater Roanoke River basin and redline (Etheostoma rufilineatum) and greenside darters (E. blennioides) of the upper Tennessee River basin. I found that endangered P. rex persists in seven isolated populations. Within populations, individuals exhibit extensive dispersal and gene flow, which maintains connectivity throughout entire watersheds. Most populations exhibit small contemporary effective population sizes and occupy few stream channels, and thereby face an elevated risk of extinction. Genetic estimates of divergence indicate that fragmentation was recent, coincident with the construction of major dams throughout the species' range. Close evolutionary relationships between most populations suggest that a translocation strategy could decrease extinction risks. I developed a framework to help guide the process of balancing small-population versus translocation risks when formulating conservation strategies. When the framework was applied to populations of P. rex, straightforward management prescriptions emerged. The framework also may prove useful for other fragmented species. Unlike P. rex, E. rufilineatum and E. blennioides are relatively abundant where they occur. However, both species were strongly affected by fragmentation due to hydroelectric dams and reservoirs. Populations in small streams flowing directly into a reservoir had lower genetic diversity than populations in larger, more fluvially connected streams. Furthermore, indices of watershed urbanization (e.g., percent impervious surface, road density) were negatively correlated with genetic diversity and with a genetic index of population stability. This suggests that darters occupying isolated streams and/or urbanizing watersheds experience smaller, more variable population sizes than darters elsewhere. Monitoring of such genetic responses could provide a useful early indicator of ecosystem stress and a useful complement to other biomonitoring techniques. / Ph. D.

Knowledge of species occurrence is a prerequisite for efficient and effective conservation and management. Unfortunately, knowledge of species occurrence is usually insufficient, so models that use environmental predictors and species occurrence records are used to predict species occurrence. Predicting the occurrence of stream fishes is often difficult because sampling data insufficiently describe species occurrence and important environmental conditions and predictive models insufficiently describe relations between species and environmental conditions. This dissertation 1) examines the sufficiency of fish species occurrence records at four spatial extents in Virginia, 2) compares modeling methods for predicting stream fish occurrence, and 3) assesses relations between species traits and model prediction characteristics. The sufficiency of sampling is infrequently addressed at the large spatial extents at which many management and conservation actions take place. In the first chapter of this dissertation I examine factors that determine the sufficiency of sampling to describe stream fish species richness at four spatial extents across Virginia using sampling simulations. Few regions of Virginia are sufficiently sampled, portending difficulty in accurately predicting fish species occurrence in most regions. The sufficient number of samples is often large and varies among regions and spatial scales, but it can be substantially reduced by reducing errors of sampling omission and increasing the spatial coverage of samples. Many methods are used to predict species occurrence. In the second chapter of this dissertation I compare the accuracy of the predictions of occurrence of seven species in each of three regions using linear discriminant function, generalized linear, classification tree, and artificial neural network statistical models. I also assess the efficacy of stream classification methods for predicting species occurrence. No modeling method proved distinctly superior. Species occurrence data and predictor data quality and quantity limited the success of predictions of stream fish occurrence for all methods. How predictive models are built and applied may be more important than the statistical method used. The accuracy, generality (transferability), and resolution of predictions of species occurrence vary among species. The ability to anticipate and understand variation in prediction characteristics among species can facilitate the proper application of predictions of species occurrence. In the third chapter of this dissertation I describe some conservation implications of relations between predicted occurrence characteristics and species traits for fishes in the upper Tennessee River drainage. Usually weak relations and variation in the strength and direction of relations among families precludes the accurate prediction of predicted occurrence characteristics. Most predictions of species occurrence have insufficient accuracy and resolution to guide conservation decisions at fine spatial grains. Comparison of my results with alternative model predictions and the results of many models described in peer-reviewed journals suggests that this is a common problem. Predictions of species occurrence should be rigorously assessed and cautiously applied to conservation problems. Collectively, the three chapters of this dissertation demonstrate some important limitations of models that are used to predict species occurrence. Model predictions of species occurrence are often used in lieu of sufficient species occurrence data. However, regardless of the method used to predict species occurrence most predictions have relatively low accuracy, generality and resolution. Model predictions of species occurrence can facilitate management and conservation, but they should be rigorously assessed and applied cautiously. / Ph. D.

Orientador: Domingos Garrone-Neto / Resumo: Neste trabalho estudamos a composição, distribuição e história natural da comunidade de peixes em um riacho litorâneo da Mata Atlântica. Além disso, relatamos um estudo de caso envolvendo a utilização desta ictiofauna como ferramenta de divulgação e conscientização ambiental, no âmbito do projeto “Peixes do Lagamar”. Conduzimos os estudos ictiofaunísticos em três trechos do rio das Minas, no município de Cananeia, litoral sul do estado de São Paulo. Apesar de estar localizado, em sua maior parte, dentro do Parque Estadual do Lagamar de Cananeia, o rio das Minas não possuía registros a respeito de sua ictiofauna. Realizamos observações diretas (mergulho livre) e indiretas (BRUVS – Baited Remotely Underwater Video Station) durante dois anos (2017 e 2018) e coletas tradicionais (covo, picaré, puçá etc.) somente em uma campanha (set./2017). Ao todo, registramos 31 espécies, pertencentes a 14 famílias e cinco ordens, com 28 espécies no trecho a jusante, 17 no trecho intermediário e seis a montante, fato que esteve relacionado ao gradiente altitudinal existente entre os pontos de coleta. Descrevemos dois comportamentos para Geophagus brasiliensis: i) uma nova tática de forrageamento e ii) uma associação alimentar do tipo “nuclear-seguidor” com o lambari Deuterodon iguape. De forma complementar, realizamos estudos de capacidade de suporte no rio das Minas e em um outro riacho da região, o rio Mandira, identificando áreas com potencial de receber visitantes para a prática de atividad... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, we study the composition, distribution and natural history of the fish community in a coastal stream of the Atlantic Forest. In addition, we report a case study involving the use of this ichthyofauna as a tool for dissemination and environmental awareness, within the scope of the "Peixes do Lagamar" project. We conducted the ichthyofaunistic studies in three stretches of the Rio das Minas, in the municipality of Cananeia, south coast of the state of São Paulo. Despite being located, for the most part, within the Lagamar de Cananeia State Park, the Rio das Minas had no records regarding its ichthyofauna. We conducted direct observations (snorkelling) and indirect observations (BRUVS - Baited Remotely Underwater Video Station) for two years (2017 and 2018) and traditional captures (fish trap, seine net, dip net and hook) in only one campaign (sep/2017). In total, we recorded 31 species, belonging to 14 families and five orders, with 28 species in the downstream section, 17 in the intermediate section and six upstream, a fact that was related to the altitudinal gradient existing between the collection points. We describe two behaviours for Geophagus brasiliensis: i) a new foraging tactic and ii) a "nuclear-follower" food association with tetra Deuterodon iguape. In addition, we carried out studies of carrying capacity in the Rio das Minas and another stream in the region, the Rio Mandira, identifying areas with potential to receive visitors for the practice of flot... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-07-29T16:21:17Z (GMT). No. of bitstreams: 1 Dissertacao Luciano Lajovic Carneiro.pdf: 507309 bytes, checksum: b58c6af9d894c2d90f75adfed8ebd925 (MD5) Previous issue date: 2011-04-18 / This research aims to assess the fish biodiversity of the streams of the Tocantins and Araguaia basin and test the relative influence of local and regional processes in determining local species richness by examining the relationship between local species richness and regional species richness. For this purpose were sampled 18 streams in the basin of the Araguaia River and 16 streams in the basin of the Tocantins River in the state of Goiás using trawls. For analysis of richness observed was used and linear regression to assess the relationship of local and regional richness. The average value of diversity index of Shannon-Wiener were similar (p> 0.098) to the streams of the Tocantins (H`= 1.784) and Araguaia (H` = 2.254), uniformity also showed similar values (p> 0.962), but the average richness values were different (p = 0.039) for the basin of Tocantins S = 7.12 and S = 11.38 for Araguaia basin. Species richness of the Araguaia streams was strongly related to regional richness (r² = 0.826, p <0.0001) indicating a linear relationship and suggesting that local assemblies are unsaturated. For Tocantins streams was obtained a weak relationship (r²= 0.251, p = 0.047) and it was not possible to infer the shape of the relationship, several factors may be involved in the result. The diversity index was not an efficient descriptor of biodiversity, the test of the relationship between local and regional richness is a good predictor of ecological processes that influence species richness, has the disadvantage of the need to obtain a large amount of data. / Este trabalho objetiva avaliar a biodiversidade de peixes de riachos da bacia Tocantins e Araguaia e testar a influência relativa dos processos locais e regionais na determinação da riqueza de espécies locais através da análise da relação entre a riqueza de espécies local e a riqueza de espécies regional. Para isso, foram amostrados 18 riachos na bacia do Araguaia e 16 riachos na bacia do Tocantins no estado de Goiás utilizando redes de arrasto. Para análise da biodiversidade foi utilizada a riqueza observada e a regressão linear para avaliar a relação entre a riqueza local e regional. Foram capturados 2919 peixes (1833 da bacia do rio Araguaia e 1082 da bacia do rio Tocantins) distribuídos em cinco ordens, 20 famílias e 85 espécies. Os valores médio do índice de diversidade de Shannon-Wiener foram semelhantes (p>0,098) para os riachos da bacia do Tocantins (H`= 1,784) e Araguaia (H`= 2,254), a uniformidade também apresentou valores semelhantes (p>0,962), no entanto, a riqueza média apresentou valores distintos (p=0,039) para as bacias do Tocantins S= 7,12 e do Araguaia S= 11,38. A riqueza de espécies dos riachos do Araguaia esteve fortemente relacionada a riqueza regional (r² = 0,826; p<0,0001) indicando relação linear e sugerindo que as assembléias locais estão insaturadas. Para os riachos do Tocantins obteve-se uma relação fraca (r²= 0,251; p= 0,047), de forma que não foi possível inferir sobre a forma da relação, pois diversos fatores podem estar envolvidos no resultado obtido. O índice de diversidade não foi um descritor eficiente da biodiversidade, por outro lado, o teste da relação entre a riqueza local e regional é um bom preditor dos processos ecológicos que influenciaram a riqueza de espécies, mas tem como desvantagem a necessidade de se obter grande quantidade de dados.

No description available.

Positive biotic interactions such as mutualism, commensalism and facilitation are ubiquitous in nature, but historically have received considerably less research attention than negative interactions such as competition, predation and parasitism. The paucity of research on positive interactions is particularly evident in stream ecosystems and in vertebrate communities. Stream fishes clearly provide an ideal system for advancing research on positive interactions. Many minnows (Cyprinidae) of eastern North America engage in a potentially mutualistic reproductive interaction known as nest association, in which individuals of one species (nest associates) spawn in nests constructed by host species. In nest association, hosts provide unsilted gravel substrate for spawning nest associates, and increased parental care to associate broods. High associate: host egg ratios can create a dilution effect, reducing the probability that host eggs will be preyed upon by egg predators. Nest associative interactions are common, but are relatively understudied compared to other interactions among stream fishes. The goals of this study were to apply general ecological models to this novel system to (a) gain new insight into the mechanisms structuring nest associative stream fish communities, and (b) to use inference from stream fish communities to potentially expand and improve the general ecological models. These goals required completion of three objectives, including (1) examining the influence of abiotic and biotic contexts on reproductive behavior and fitness outcomes between a cyprinid host and associate, using the biological markets model to generate predictions; (2) examining the utility of the nest web framework (previously only used for cavity nesting vertebrate communities) and the stress gradient hypothesis (previously applied almost exclusively to plant communities) for predicting which associate species spawn on nests built by various nest building species, and the consequences of these choices, respectively; and (3) using two-species occupancy modeling to determine the relative influence of biotic interactions and habitat covariates on the co-occurrence of a host and two nest associates. To accomplish these goals, I conducted a large-scale experiment to manipulate presence of mutualists (Nocomis leptocephalus, host; Chrosomus oreas, associate), egg predators (biotic context) and habitat quality (abiotic context). I conducted behavioral nest observations and conducted repeated stream fish stream fish community surveys to collect demographic data. I constructed a nest web from observational data, and implemented structural equation modeling through an information-theoretic framework to identify nest web plausibility across a large spatial extent. I tested some predictions of the stress gradient hypothesis by regressing juveniles-per-nest and a metric of cyprinid community structure on a composite measure of physical stress (scaled gradients of catchment-scale agricultural land use and catchment area). I used two-species occupancy modeling to model co-occurrence of N. leptocephalus hosts and two associates, C. oreas and Clinostomus funduloides, and used an information-theoretic framework to compare hypotheses representing the importance of biotic interactions, habitat covariates or both at determining species co-occurrence. Results corroborated some (but not all) model predictions, and identified room for improvement in each of the general models. Nest associative spawning by C. oreas was not context dependent; C. oreas did not spawn in the absence of a reproductively active male N. leptocephalus at any treatment level. However, the net fitness outcome of host and associate species was mutualistic, and the interaction outcome switched from commensalistic to mutualistic with abiotic context. N. leptocephalus reproductive success was improved by C. oreas presence in less-silted habitats, but not in heavily-silted habitats. This is most likely because broods were subject to predation in both habitat types, but were also negatively affected by siltation in silted habitats. Accordingly, egg dilution by associates was not sufficient to support a mutualistic relationship in less favorable habitats. Results suggest that the biological markets model may be a useful tool for predicting fitness outcomes of nest associative mutualism, but may not be as useful for predicting the behavioral outcomes of obligate mutualisms. Future applications of the biological markets model should carefully consider species traits, specifically the degree to which trading behavior is obligate for participants. Future work with this model will yield more insight by considering highly facultative associates. Nest webs constructed from nest observational data suggested an interaction topology in which strong (nearly-obligate) associates relied most frequently on N. leptocephalus nests, and less frequently on nests constructed by Campostoma anomalum. Weak (facultative) associates were seldom associated with nests constructed by either species, and probably spawned before hosts began nesting activity. Structural equation models corroborated this topology throughout the New River basin, although some less-supported model evidence specified some nest association by weak associates. Juveniles-per-nest of strong associates responded positively to physical stress, while this metric for other cyprinid reproductive groups showed no relationship. Proportional representation of Nocomis and strong associates also increased predictably with physical stress. This study suggests that the nest web framework can be informative to systems outside the ones for which it was developed; future studies may be able to use this framework to better understand the role of habitat-modifying species in communities other than cavity nesting terrestrial vertebrates and nest associative stream fishes. This work extended the nest web framework by (a) modeling the outcomes of interactions instead of the interactions themselves, and (b) by using structural equation modeling to test nest web predictions with an information-theoretic framework. This study also suggests that the stress gradient hypothesis can be useful for understanding interaction dynamics in vertebrate communities; this represents the first direct evidence that this model can be used in vertebrate communities. Further, I demonstrate that the stress gradient hypothesis may be extended to predict community structure. However, more research in a diversity of systems will be needed to determine the extent to which this can be applied. This study provides some of the first evidence of large-scale positive co-occurrence patterns in vertebrates. However, the precise roles of habitat covariates and biotic interactions were species-specific. Occupancy results suggest that co-occurrence between N. leptocephalus and nest associate C. funduloides is driven only by reproductive behavioral interactions. Alternatively, evidence suggests that co-occurrence between N. leptocephalus and C. oreas is driven by both nest association and habitat covariates. That two-species occupancy modeling can be a useful tool for comparing difficult-to-test hypotheses involving biotic interactions at large spatial scales. This study represents the first quantitative, multi-scale treatment of positive interactions in stream ecosystems. This study demonstrates that applying general ecological models to stream fish communities can yield new insights about both the study system and the models themselves. While models of negative interactions, food webs and dispersal have been applied to stream fishes, we stand to gain much ground by also considering positive biotic interactions. In doing so, stream fish ecologists will also be able to contribute to the advancement of general ecology, and thus raise awareness for these understudied ecosystems and taxa. / Ph. D.