Effects of regulated flows on habitat use of the robust redhorse, an imperiled riverine fish

The robust redhorse Moxostoma robustum is a rare and imperiled fish found only in three drainages from North Carolina to Georgia, USA.  Hydroelectric dams have altered habitat and restricted its range.  Blewett Falls Dam on the Pee Dee River in North Carolina is hydro-regulated, and a new minimum flow regime that will affect available habitat for robust redhorse is being implemented.  Our objectives were to describe and quantify spawning and non-spawning microhabitat and quantify how these will be affected after the implementation of augmented minimum flows.  Microhabitat use data were obtained from relocated radio-tagged robust redhorse from spring 2008 through summer 2009.  Non-spawning habitat consisted of deep, slow-moving pools with bedrock and sand substrates with boulders or coarse woody debris cover.  Spawning habitat consisted of shallower, faster-moving water with gravel and cobble substrate and boulders as cover associated with shoals, although overlap in habitats between spawning and non-spawning occurred.  Microhabitat suitability analysis suggests the augmented flows will increase suitable habitat during spawning and non-spawning periods.  Our results will assist managers in refining the regulated flows in the Pee Dee River and other waters to enhance habitat for the robust redhorse and other fish populations.