Survey of the freshwater mollusk assemblages in the Little River, Virginia.
May 2010 - December 2011
- Virginia Department of Game and Inland Fisheries
PROJECT DESCRIPTION: The Little River is a relatively undisturbed headwater tributary of the Clinch River that still supports at least 12 freshwater mussel species, including the federally endangered shiny pigtoe, Fusconaia cuneolus and littlewing pearly mussel (Pegias fabula). The most comprehensive survey of the stream was conducted 20 years ago. We are repeating surveys at those survey locations using semi-quantitative methods intended to detect rare species and quantitative methods to establish base-line data for monitoring purposes and population estimates. These efforts will be coupled with fish assemblage surveys conducted by VDGIF and TVA. OBJECTIVES: 1) Detect endangered species and document native mollusk assemblages at 16 sites in the Little River originally visited by biologist in 1990; and 2) Determine density at selected sites in the Little River. PROGRESS: As of August 2011, we have semi-quantitatively sampled 21 sites in the Little River, documented and described habitat, determined the amount of habitat surveyed, measured all live mussels, and noted the presence of other aquatic mollusks (snails and clams). We have documented live specimens of 11including the state-endangered Alasmidonta viridis and a federal candidate for threatened status, Ptychobranchus subtentum. We found relic shells of the federally endangered, Quadrula cylindrica strigillata and Pegias fabula and a relic shell of the state-endangered Lasmigona holstonia. We also observed several relic shells of the state-threatened Io fluvialis. Our greatest challenge has been obtaining permission to access sites in the Little River. We have spent considerable time contacting and coordinating visits with land owners. We now have a more complete picture of the spatial variation among sites in the Little River. In general, there appears to be a great amount of variation in total richness and relative abundance among sites; however, there are a few patterns of note. As expected, there is increasing richness from upstream to downstream, but this is limited to the upstream third of the river. Species richness varies greatly in lower two-thirds of the river. While relative abundance varies greatly throughout the river, many sites in the middle of the river have extremely low numbers of mussels as well as limited species richness. Instream physical habitat does not appear to explain the limited richness and abundance, nor does local land use. These three sites flow through a landscape of forest or pasture well buffered by an extensive forested riparian zone.