Document Type

Original Research Article


Population fragmentation by dams of all sizes is a major threat to biodiversity in running waters. Dam removal has become an increasingly popular tool among conservation practitioners because of its potential benefits to aquatic organisms and ecosystems. During fish monitoring following removal of a small run-of-river dam on the Cahaba River, we documented new upstream records between 8 months and 2 years post-removal for five species: Stargazer Shiner, Notropis uranoscopus; River Redhorse, Moxostoma carinatum; Southern Sand Darter, Ammocrypta meridiana; Freckled Darter, Percina lenticula; River Darter, P. shumardi. These new records suggest that the former dam may have served as a barrier to dispersal of resident species, and that dam removal may have benefited these species by opening additional habitat to colonization.


Upon re-examination of records provided by the Geological Survey of Alabama (GSA), we discovered that a data-reporting error (a shift in rows which caused abundances to align with incorrect species) caused inaccurate species presence for a single site ~1 km (latitude: 33.175, longitude: -87.028) upstream of the Marvel Slab dam in 2004 prior to removal. Because one species in our study was inaccurately reported at this site, we gave a lesser range extension (~ 1 river km) than actually occurred. Prior to dam removal in 2004 the upstream range extent for Skygazer Shiner, N. uranoscopus, was downstream of the Marvel Slab near the junction with the Little Cahaba River and our post-removal sampling of the species represents a >22 river km extension. The small range extension for River Redhorse, Moxostoma carinatum (~1 km), is correct as originally reported based on GSA sampling records, as this species was collected just above the dam in 2004 prior to removal. The error affected only a single sample at a single site and other GSA data was found to be accurate. By increasing the number of large upstream range extensions (from three to four species), this correction adds support to the idea that the removal of the Marvel Slab opened upstream habitats to a diverse group of fishes.



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