Thesis Title

The Effects of Bridge Crossings on Fish Assemblages in a Southwest Missouri Stream


Matt Keener

Date of Graduation

Summer 2003


Master of Science in Biology



Committee Chair

Daniel Beckman


Recent concerns over water quality have suggested a need for the establishment of a baseline of the current conditions of Missouri's aquatic resources. One region of concern due to impacts associated with increases in population and development is the Ozarks region, particularly the James and White River watersheds. The aquatic health in this region is being assessed by sampling fishes in selected streams (Bull and Swan Creek) with the goal of developing an Index of Biotic Integrity (IBI). From 1 June 2002 until 30 September 2002 I sampled fish located in the vicinity of bridge crossings in Swan Creek to determine if fish assemblages found around bridges differed from those found throughout the rest of the stream. Twenty seven species were collected at thirteen bridge sites and forty six species were collected at ten random sites throughout the stream. Overall fish density did not significantly differ between bridge sites and random sites (p=.531). Percentages of omnivores and herbivores were significantly higher at random sites (p=.001). On average, bridge IBI scores were higher (82.7) than random sites (77.2). Physical habitat measurements indicated that only canopy cover was significantly different between bridge and random sites (p=.007). IBI scores indicated that bridge crossings are not significantly different from the rest of the stream in terms of biotic integrity. Our findings suggest that bridges did not offer any beneficial habitat to fish assemblages that couldnot be found in the rest of the stream. Swan Creek is a relatively unmodified, pristine stream and provides diversity of habitat sufficient to support its fish assemblages. In a more degraded stream, bridges may in fact serve as an important artificial habitat for some species.

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