Relationship between habitat quality and occurrence of the threatened black redhorse (Moxostoma duquesnei) in Lake Erie tributaries

Recovery planning for the nationally threatened black redhorse (Moxostoma duquesnei) is limited by a lack of knowledge regarding species ecology, population size and factors that affect distribution and abundance. Generalized additive models (GAM) were used to evaluate the influence of habitat quality on the distribution of the black redhorse in the Grand River (Ontario) and 11 western Lake Erie tributaries (Ohio). Black redhorse were captured at 26% of Grand River sites and 6% of western Lake Eric tributary sites. In western Lake Erie tributaries, black redhorse were more likely to be found at sites of intermediate upstream drainage area (a surrogate for watercourse size) and less likely to be found at sites with poor substrate, pool, cover and channel conditions. In the Grand River, occurrence was negatively associated with higher gradients and small and large upstream drainage areas. Habitat quality was found to be associated with the distribution of golden redhorse (M. erythrurum) but not the other two co-occurring redhorse species. Site occupancy was negatively associated with poor substrate and pool conditions. Results from this study indicate that, in areas of black redhorse occurrence, river reaches with clean, coarse bed material, well-developed riffles and pools, and stable channels require specific protection. Repatriation efforts in formerly occupied watercourses will likely require restoration of the condition of these habitats.