Spawning Microhabitat Use of Bluehead Chubs in a Small Virginia Stream

The purpose of this study was to assess the spawning microhabitat use of bluehead chub Nocomis leptocephalus in the North Fork of the Roanoke River, Virginia. Average current velocities (ms-1) and depths (cm) of transects at nests (n=28) were compared to paired transects one meter upstream. Approximately 100 substrate particles were measured randomly from four nests and compared to 100 particles from the surrounding substrate at a relatively forested site (n=2 nests) and a relatively silted (n=2 nests). Logistic regression indicated that current velocity was the only significant habitat variable (p=0.092), which negatively affected nest presence. Paired t-tests showed that chubs prefer substrate particles approximately two millimeters smaller than available gravel both before (p=0.0001) and after (p=0.0006) accounting for land use differences. Sizes of substrate particles used by chubs were larger in the silted site than in the forested site (p=0.0187), but sizes of available substrate did not differ between the two land use types (p>0.10). Bluehead chubs are reproductive habitat specialists. Selecting larger stones to build their nests in a silted site may improve oxygenation, which can be negatively affected by siltation.