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Fish communities, water quality, instream habitat features and surrounding land use were assessed in 20 agriculturally developed watersheds in the Eastern Highland Rim of the lower Tennessee River Basin to determine if fish community composition is related to agricultural intensity (defined as the percentage of the contributing basin in row-crops). Twenty sites were selected to represent a gradient of agricultural intensities ranging from 0.7 to 30 percent in 30-100 square-mile basins. A total of 10,550 individual fish were collected during the course of the study representing 64 species and 15 families. The Cyprinids (minnows) were the most common group of fishes containing 18 species, followed by the Percids (perch and darters) with 12 species, and Centrarchids (sunfish) with 11 species.
Substrate embeddedness was the only variable correlated with both agricultural intensity and fish communities (ordination scores and several community-level metrics). Multivariate and nonparametric correlation techniques were used to evaluate the composition of fish communities with respect to natural physical and chemical variability along the agricultural gradient. Principle component analysis and correspondence analysis suggest inherent physical (elevation, channel morphology, and streamflow) and biological (fish community composition) differences. Data for the subgroup containing the largest number of sites (11) were re-analyzed, revealing that several environmental variables (nutrient concentrations, stream-gradient, bankfull-width, and substrate embeddedness) were related to agriculture, whereas others were related to fish communities. Results from this analysis suggest that although some water-quality variables and habitat altering practices are related to agricultural land use, fish communities primarily respond to the cumulative effects of embeddedness and reduced streamflow.
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