Impacts of Road Crossings on Fish Movement and Community Structure

ABSTRACT

We quantified the impact of four commonly used road crossings (bridge, arch culvert, box culvert, and pipe culvert) on stream fish community structure and movement in the Piedmont region of the Cape Fear River basin of North Carolina, USA during summer 2004. We focused on non-perched crossings, which did not present a physical barrier to fish movement. With the exception of species richness, all response variables (fish population size, species diversity, fish index of biotic integrity, and conditional percentage of movement) did not vary significantly with crossing type, position (upstream and downstream), or month. Streams with arch culverts contained significantly higher species richness than streams with bridges. The general lack of stream fish abundance and diversity responses to road crossings may be due to the insensitivity of stream fish community variables to anthropogenic effects, the insensitivity of fish communities to the presence of crossings, the overall resilience of fish communities, or the shifting baseline theory (fish communities having shifted to a different community prior to sampling). Triple-pass electrofishing results suggest that these road crossings had no detectable effect on fish abundance or diversity.