Modeling Suitable Riverine Habitat for the Robust Redhorse: An Assessment for Reintroduction

A remnant population of robust redhorse Moxostoma robustum, a rare catostomid, persists downstream of Blewett Falls hydro-facility, the terminal dam in the Pee Dee River, North Carolina.  An improved minimum flow regime for the Tillery hydro-facility, the next dam upstream of Blewett will likely enhance habitat conditions.  These habitat improvements could justify robust redhorse reintroduction into the Tillery reach that would benefit the species, but upstream physical habitat has not been quantified.  Habitat suitability indices based on field microhabitat measurements from downstream of Blewett Falls Dam were applied to model suitable habitat for proposed minimum flows.  Our objectives were to (1) quantify suitable habitat in the Tillery reach based on these suitability indices and (2) determine what specific microhabitat variables are limiting.  Modeling results indicate that suitable robust redhorse habitat exists in the lotic reach between Tillery and Blewett dams.  Sensitivity analyses suggest that substrate and depth are limiting microhabitat variables throughout the reach.  These results will assist river managers in flow regulation decisions during critical periods for the robust redhorse and other species of concern and guide research and planning for potential reintroduction of the robust redhorse in its historical range.