6th Annual Judith Ramaley Celebration of Research and Creative Scholarship
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Poster #75 Geomorphological Complexity as a Determinant of Fish Community Structure in a River Network Christopher Milham Faculty Mentor: Michael D. Delong A widely held view is that fish species richness increases as a function of an increase in river basin size. More recently geomorphic complexity, instead of location longitudinally within a river network, has been identified as a key factor in fish community structure at multiple spatial scales. Complexity is an attribute of local geology and climate independent of any continuum of physical connection. With greater complexity there is greater chance of more diverse habitat. This study examined fish community structure in longitudinally arranged patches to test longitudinal gradient and local geomorphology as determinants of community composition. We electrofished at six different sites, from low to high geomorphology complexity: Lake Pepin, Saint Croix River (2 sites), and Upper Mississippi River (3 sites). Analysis included density of each species, number of taxa, and species diversity. Geomorphological complexity was summarized by comparison of: island frequency, number of channels, wetted area width, river valley width, and sinuosity. Fish were identified and quantified as catch per unit effort. Species richness increased with greater geomorphological complexity, whereas the relationship of fish community structure to location along a longitudinal gradient was weaker. The findings, therefore, indicate that geomorphic complexity and not location on a longitudinal gradient is a critical determinant of community structure. |
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