The Effects of a Modified Flow Regime on Fish Assemblages in a Third-Order Piedmont Stream in Lee County, Auburn, Alabama
Type of DegreeThesis
DepartmentFisheries and Allied Aquacultures
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I examined the effects of a modified flow regime on fish assemblage condition over a 2-year period at two sites in Chewacla Creek, a third-order Piedmont stream (Lee County, AL). My goal was to assess the biotic condition of fish assemblages in the creek impacted by dewatered conditions that occurred prior to 2003 as a result of drought, no water releases from Lake Ogletree, and quarry mining in the watershed. The two Chewacla sites were compared with a relatively undisturbed reference site, Cane Creek (Cane-1), another Piedmont stream in Lee County. Water quality and fishes were sampled once per year at all three sites during low-flow conditions in the fall of 2004 and 2005. In addition, a physical habitat assessment at each site was conducted in the fall of 2006. The principal method used in this study for comparison of fish assemblages across sites was the Index of Biotic Integrity (IBI). Differences across sites in water quality, physical habitat quality and fish community health were compared. Results showed few differences across sites in water quality and physical habitat once continuous flows were reestablished in the study reach in December of 2003. IBI ratings for Cane-1were good to excellent; thus, it compared well with other Piedmont reference streams in terms of fish assemblage condition. In contrast, IBI ratings for the two Chewacla Creek sites (CH-U and CH-D) rated poor to fair, indicating that fish assemblages at both sites were degraded and did not meet fish assemblage conditions present at Cane-1 in either 2004 or 2005. At CH-U, IBI ratings were poor both years suggesting no recovery of the fish assemblage from altered flow conditions that occurred periodically between 1999 and 2001. At CH-D, IBI ratings changed from poor to marginally fair in 2005 suggesting slight recovery of the fish assemblage from periodic dewatering of the stream channel that occurred at the site. Differences in fish assemblage condition between Cane-1, CH-U, and CH-D were mostly attributable to differences in flow regime. Although water quality and physical habitat influenced the fish assemblages at CH-U and CH-D, a highly modified flow regime resulting from drought in previous years, mining in the watershed, and the presence of Lake Ogletree appeared to be most influential in structuring the fish assemblages at both sites during this study.