Mark-recapture studies sample unevenly over distance and generate biased or distance-weighted movement data, where short distances are sampled more frequently than long distances. I examined how study design affects the degree of distance-weighted sampling and observed movement distributions of stream fish. A modeling study illustrated how distance-weighting increases with the number of mark sites and decreases with the length of stream sampled during recapture. Sub-sampled empirical data sets indicated that longer movements can be detected by increasing the length of the recapture section and that a substantial proportion of fish may move long distances outside of study areas. I also examined factors that were associated with movement in a network of streams. The probability of emigrating from a site was positively related to intermittency and body size and negatively related to distance from the mainstem creek and habitat complexity. Movement rates, measured as the number of fish moving upstream through a trap per day, were positively related to increases in flow, daylength, and water temperature. Distance moved was greater for fish that were initially marked within intermittent reaches. Overall, some species moved in association with several of these factors but others did not respond to any factors. Finally, I identified species-level attributes that were associated with colonization rates after experimental defaunation. Movement rate and abundance explained the most interspecific variation in colonization rates when compared to competing predictors (spatial distribution, body size, and family). Recovery occurred slowly and several species had not restored more than half of their pre-defaunation abundance within a year. Despite slow recovery for some species, defaunation had only a short-term (i.e., < 3 months) effect on relative abundance patterns. This study has important implications for conservation. Improvements in study design will allow detection of longer movements that may be a key component of species invasions, demographic rescue, and colonization. Species that move in association with multiple factors may be better colonists than species that do not. Finally, species that are rare and less-mobile will recover their populations slowly and will be vulnerable to extirpation in systems impacted by frequent pulse disturbances. / Ph. D.

Mutualism is an understudied phenomenon across taxa, but is important to the persistence and structure of communities. The role of positive interactions in supporting threatened species is critically important given that freshwater fish are extremely vulnerable due to the combined effects of climate change and habitat degradation. To disentangle complex positive multi-species interactions, I applied both Eltonian and Hutchinsonian niche approaches to the reproductive mutualism of leuciscids known as nest association, a form of alloparental care characterized by an adult of one species guarding the offspring of another. I conducted this study with the leuciscid community of Toms Creek in which Bluehead Chub Nocomis leptocephalus is the primary nest builder and nest associate species include Rosyside Dace Clinostomus funduloides, Rosefin Shiner Lythrurus ardens, Mountain Redbelly Dace Chrosomus oreas, Crescent Shiner Luxilus cerasinus, White Shiner Luxilus albeolus, Central Stoneroller Campostoma anomalum, Creek Chub Semotilus atromaculatus, and Blacknose Dace Rhinycthys atratulus. I applied Hutchinsonian niche theory with respect to hydrology and water temperature to define the reproductive phenology of each species involved in the reproductive mutualism, then used Eltonian niche theory to define the role of each species in parental and alloparental care. My dual niche theory approach elucidates the reproductive requirements of each species and quantifies the contribution of nest associates to alloparental care, which historically have not been included in definitions of nest association. My results show that Blacknose Dace Rhinichthys atratulus and Creek Chub Semotilus atromaculatus are not true nest associates of Bluehead Chub Nocomis leptocephalus based on their reproductive phenology and observed nesting behaviors. In contrast to previous work on nest association, most associate species did contribute to parental care through nest defense and vigilance behaviors, and their specific behaviors were influenced by morphology. By clearly defining the reproductive niches of these species, this study lays the groundwork for future investigation of how various climate scenarios may impact multi-species reproductive mutualisms. / Master of Science / Positive interactions are understudied throughout ecology, but are important to the persistence and structure of communities. The role of positive interactions in supporting threatened species is critically important given that freshwater fish are at high risk of extinction due to the combined effects of climate change and habitat degradation. To understand the complex positive interactions in freshwater fish, I applied both niche theory approaches to a mutualistic reproductive interaction known as nest association, where an adult of one species builds a nest on which it guards the offspring of other species (formally: a type of alloparental care). I conducted this study with the leuciscid (commonly known as minnow) community of Toms Creek in which Bluehead Chub Nocomis leptocephalus is the primary nest builder and nest associate species include Rosyside Dace Clinostomus funduloides, Rosefin Shiner Lythrurus ardens, Mountain Redbelly Dace Chrosomus oreas, Crescent Shiner Luxilus cerasinus, White Shiner Luxilus albeolus, Central Stoneroller Campostoma anomalum, Creek Chub Semotilus atromaculatus, and Blacknose Dace Rhinycthys atratulus. For each species involved in the reproductive mutualism, I defined the seasonal timing of reproduction with respect to hydrology and water temperature, then defined their role in parental and alloparental care. My approach clarifies the reproductive requirements of each species and establishes the contributions of associate species to alloparental care, which historically have not been included in definitions of nest association. My results show that Blacknose Dace Rhinichthys atratulus and Creek Chub Semotilus atromaculatus are not true nest associates of Bluehead Chub Nocomis leptocephalus based on their reproductive requirements and observed nesting behaviors. In contrast to historic descriptions of nest association, most associate species did contribute to parental care through nest defense and vigilance behaviors, and their specific behaviors were influenced by their size and physical adaptations. By clearly defining the reproductive needs and roles of these species, this study lays the groundwork for future investigation of how various climate scenarios may impact positive relationships among species.