R.K. Smith and D.J. Orth, Dept Fisheries and Wildlife
Sciences, Virginia Tech, Blacksburg, Virginia 24060; Voice 540-231-5320 FAX 540-231-7580
E-Mail rysmith6@vt.edu
Keywords: stream, microhabitat selection, reproductive guilds,
refugia, bed movement
Alterations of sediment dynamics in spawning habitats have been
implicated in declines of several stream fishes. For example, increased levels and
frequency of bed movement during egg incubation periods may result in reduced reproductive
success. Adaptation to bed movement by selection of spawning microhabitat refugia was
investigated in the upper Roanoke River, Virginia, a watershed heavily impacted by
agriculture and urbanization. Spawning areas of several darters, minnows, and suckers
representing 3 reproductive guilds were identified through snorkeling observations.
Microhabitat use and availability were measured to investigate habitat selection. Logistic
regression analysis indicated that nest spawning darters selected strongly for large
particle sizes and low embeddedness. Nest building chubs utilized areas of low
embeddedness, low velocity, and relatively laminar flow. Simple lithophilic spawners
selected distinct ranges of substrate size, velocity, depth and shear stress. Spawning
microhabitat selection in all 3 reproductive guilds has the potential to mitigate for bed
turnover in floods. Stability of these spawning microhabitats has also been empirically
evaluated with tracer particles and repeated measurements of monumented cross-sections to
validate these conclusions.
