Graduate Thesis Or Dissertation
 

Formation and maintenance of fish assemblages in a high desert Oregon stream

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9w0327344

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  • Considerable controversy exists about how fish assemblages are organized. I explicitly took fish movement into account while I studied the effects of disturbance, habitat complexity, and predation at different times of the summer to understand the major factors influencing assemblage structure in a high desert Oregon stream. The effects of disturbance were determined by sampling fish assemblages before and after summer and spring floods. Proportions of fish density and diversity decreased more in simple habitats than in complex ones following a summer flood and assemblages were quite resilient in all habitats. Following these floods, three controlled field experiments were performed to investigate fish assemblage formation and maintenance in response to habitat complexity and predation. Experiments were designed to allow fish to move in and out of manipulated habitats. Complex habitats from these experiments had higher juvenile and adult fish densities and diversities than simple habitats. Simple habitats had a high proportion of age 0+ fish and low species richness. Pool habitats with high densities of squawfish predators (>0.22 squawfish/m³) had lower fish densities and diversities than pools with low squawfish densities. Pools with high densities of predators had a high proportion of age 0+ fish, few juvenile suckers, and low species richness. Migration of fish during the spring and summer was the dominant feature affecting fish density and assemblage structure in Rock Creek. Habitat complexity, predation, and disturbance altered the patterns of migrations into different habitat types in Rock Creek. Migrations of fish resulted in an increase in diversity and density which peaked in late summer. A suite of models are presented that assume increasing fish density and diversity with time as a template. The affects of variations in habitat complexity, predator density, and disturbance timing alter the trajectory of the template in different ways. For example, summer floods are predicted to have greater effects on the template than spring floods. In addition, complex habitats and pool habitats with high densities of squawfish predators are predicted to have higher fish colonization rates than simple habitats and pools with low densities of squawfish predators, and these rates diverge through time. Application of these models to fish assemblages in other streams is related to distances from colonization sources and regional and environmental contexts.
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Declaración de derechos
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  • File scanned at 300 ppi (Monochrome, 256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9050C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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file details PearsonsToddN1995.pdf 2017-10-19 Público Descargar