Spring-fed streams in Virginia and assessment of livestock impacts

Abstract

The first of two studies surveyed fish communities and habitats in first-order spring streams in Virginia. Springs exhibited low species (3.3) and trophic guild (2.5) richness, and fish densities averaged 0.47 individuals/m². Two species, blacknose dace (Rhinichthys atratulus) and sculpins (Cottus sp.) dominated most sites. Spring size and location factors more effectively predicted fish community structure than did instream habitat or riparian condition, indicating that composition of Virginia spring fish communities was limited by access to colonization sources. Location, size, and instream habitat of springs were related to presence of common fish species and trophic guilds.

The second study evaluated livestock impacts on biotic communities of ten Virginia spring streams. Riparian and instream habitat was significantly altered and nitrate levels were elevated in heavily grazed watersheds. Within the fish community, piscivores and young-of-year benthic invertivores were adversely affected by habitat loss associated with increasing cattle densities. Benthic macroinvertebrate communities showed significant trends in composition across the gradient of grazing intensities. Fish communities were correlated with riparian condition, whereas benthic invertebrate communities were correlated with benthic habitat degradation and nitrate enrichment. Benthic macroinvertebrate community structure was a reliable indicator of cattle-related spring stream degradation, but fish metrics were related to riparian condition.