Habitat analysis by hierarchical scheme and stream geomorphology (West Virginia)

A study was undertaken to classify eight stream reaches in the North Branch of the Potomac River watershed and determine if geomorphologic differences influenced the availability of fish habitat structure and fish density. Stream reaches were classified using Rosgen Level II (1996) methods, and fish habitat was determined using Hydraulic Channel Unit (HCU) classification based on a method modified from Bisson et al. (1982). Other habitat variables were also studied such as stream shading and physical habitat based on the Rapid Bioassessment Protocol (Barbour et al. 1999). Despite the differences in HCU density between sites, HCU density did not influence fish density in the study streams. HCU density appeared to be mainly controlled by slope. Fish densities were highest in the relatively unimpacted streams, as expected. However, the impacted streams also appeared to have sufficient physical fish habitat structure to support fishes historically found in these streams. Other confounding variables, such as acid mine drainage, may be controlling factors in inhibiting fish populations in the impacted streams.