Reproductive ecology and seasonal migrations of robust redhorse (Moxostoma robustum) in the Savannah River, Georgia and South Carolina

The objectives of this dissertation were to (1) establish a reliable means of sampling robust redhorse and other catostomid fishes for the purpose of broodstock collection and research; (2) determine the patterns of seasonal migration, daily movement, and habitat use of robust redhorse; and (3) evaluate the degree of spatial and temporal segregation of spawning habitat occurring among catostomid species on main channel gravel bars in the Savannah River, South Carolina and Georgia. The use of prepositioned grid electrofishers was determined to be viable and in many ways superior method for both collecting robust redhorse broodstock and sampling catostomid spawning aggregations. This method proved particularly effective in collecting ripe females when used in conjunction with an observation tower. Robust redhorse were found to be a highly mobile species making long distance migrations between spawning and overwintering habitats. However, they tended to maintain small daily use areas less then one kilometer in length. Robust redhorse were found to inhabit deep water along the outside bends of the river in close association with gravel substrate and woody debris. This species was also shown to exhibit a high degree of fidelity to both spawning and overwintering habitats. Catostomids appear to have specific spawning microhabitat preferences. Although some temporal and spatial overlap was observed, these preferences allowed adult Savannah River catostomids to effectively partition available spawning habitat. Frequent temporal overlap between the early life history stages of one species and the spawning adults of another occurred. There is also evidence to suggest that intraspecific superimposition of nest sites occurs.