Jennifer C. Wellman, Daniel L. Combs, and S. Bradford
Cook, Department of Biology, Tennessee Technological University, Cookeville, TN 38505
Voice 931-372-3134 E-Mail JCW3866@tntech.edu
Keywords: bridge construction, environmental impacts, fish
communities, water warm streams
The effect of bridge/culvert construction/replacement was studied on 42
streams in two ecoregions of Tennessee. Bridges were placed in three age classes (0-5
years old, 5-10 years old, and 10+ years old), and sampled biannually for two years. Three
100-m long stream reaches were sampled at each bridge with a 50-m buffer zone separating
each site. Sites were located upstream from, at, and downstream from bridges. In each
100-m reach, fish communities were sampled by a single pass depletion using a backpack
electrofishing unit. Physical and chemical characteristics were measured to correlate with
fish community data. Funding was provided by the Tennessee Department of Transportation
and the Center for the Management, Utilization, and Protection of Water Resources at
Tennessee Technological University.
Eighteen Paired t-tests were conducted to compare richness between
upstream and bridge sites; all but one was not significant (Significant test: P = 0.02;
Non-significant tests: P = 0.09- 1.00), and only one was significant between the bridge
and lower site(Significant test: P = 0.04; Non-significant tests: P = 0.06 - 1.00).
Diversity did not differ between bridge and lower sites (18 Paired t-tests, P = 0.06 -
0.95), and only in two diversity tests between upstream and bridge sites(Significant
tests: both P = 0.02; Non-significant tests: P = 0.06-0.98). Of the four significant
tests, three indicated that richness and/or diversity was greater at bridges than at lower
or upper sites. This study does not support the view of some conservation groups that
bridge construction has long-term negative impacts on fish communities. However, immediate
impacts of bridge construction were not evaluated in this study, and bridges may provide
access for activities that are detrimental to fish communities (e.g., gravel dredging).