Michael M. Gangloff1, Emily E. Hartfield2, Kevin L. White1, David C. Werneke2, and Jack W. Feminella2. (1) Biology Department, Appalachian State University, 572 Rivers Street, Boone, NC 28608, (2) Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849
Although the impacts of large dams to fluvial ecosystems are frequently dramatic and have been well documented, impacts of smaller structures remain under-studied. A comprehensive understanding of the impacts of low-head dams (i.e., those <5 m height) is critical to imperiled species management because 1) low-heads greatly outnumber larger dams and 2) dam removal is increasingly part of stream restoration projects. During 2006 and 2007 we quantified responses of invertebrate and fish assemblages at 18 small Alabama dams. We categorized dam status as intact, breached, or relict. Preliminary data indicate that responses ranged widely between taxa and appeared related to dam status. For example, crayfish were less abundant downstream from 16 of the 18 dams but differences were most dramatic immediately downstream of intact dams. In contrast, we measured much greater mussel densities immediately downstream of some intact dams and we found that mussel extirpations were greatest near breached or relict dams. These data suggest that the response of invertebrate populations to small dams and changes in physicochemical conditions varies widely between taxa with different life histories. Further, they suggest that extensive case-by-case studies are needed to weigh consequences of dam removal or restoration for at-risk freshwater taxa.
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dams, mussels, restoration