Habitat Partitioning and Associated Morphological Differences Among Three Species of Catostomidae (Teleostei: Actinopterygii) in the South Fork Roanoke River, Virginia

The upper Roanoke River has 11 species of Catostomidae including Thoburnia rhothoeca, Torrent Sucker; Moxostoma cervinum, Blacktip Jumprock; and Moxostoma ariommum, Bigeye Jumprock. Resource partitioning appears to be a key component of maintaining diverse fish assemblages with habitat and food partitioning cited as especially important in communities containing members of the same family. The diets of these species have been documented in previous work revealing only modest differences among them. Snorkeling observations and subsequent quantification of microhabitat were conducted to illuminate habitat partitioning among these morphologically and ecologically similar species. Thoburnia rhothoeca inhabited the shallowest, fastest water, over the smallest substrate, and Moxostoma ariommum inhabited the deepest, slowest water, over the largest substrate, with M. cervinum intermediate for all habitat variables. In an effort to correlate morphological adaptations to these different microhabitats, 22 body measurements were included in a Principal Components analysis revealing a bigger eye for M. ariommum and more fusiform bodies for T. rhothoeca and M. cervinum consistent with findings in other species inhabiting faster waters. Other correlations among morphology and microhabitat were less clear

Microhabitat Comparison of Percina roanoka (Roanoke Darter) and Percina nevisense (Chainback Darter) in the Roanoke River

Snorkel observations of Percina roanoka and P. nevisense in the Roanoke River during summer months were followed by measuring current velocity, water depth, and substrate diameter at points of occupation. A total of 89 observations of P. roanoka and 81 observations of P. nevisense were compared using two-sample T-tests. Percina roanoka inhabited faster, shallower water than P. nevisense with the former found in a mean flow of 0.318 m/s and depth of 31.53 cm and the latter in a mean flow of 0.17 m/s and depth of 55.6 cm. Mean diameter of substrate at points of occupation did not differ significantly between the two species with P. roanoka over substrate 10.14 cm diameter, and P. nevisense over substrate of 9.7 cm diameter. Differences in habitat among age classes were not detected for either species. These findings suggest habitat partitioning along current velocity and depth help maintain the diverse darter assemblage in the Roanoke River