Species Associations and Habitat Use of Stream Fishes: the Effects of Unaggregated-Data Analysis

Abstract

ABSTRACT Fish species in several families were collected in microhabitat quadrats during warmer seasons of 1989–1990 in the upper Roanoke River (URR), a midsized stream of southwestern Virginia. The quadrats were visually classified into five mesohabitat types (medium and shallow pools, runs, and slow and fast riffles) before sampling. Uni-, bi-, and multivariate statistical analyses on fish-abundance data were used to establish species associations, fish-habitat relations, and habitat-use guilds. This included examination of coefficients of variation for species densities across quadrats, ANOVAs for species densities across different habitat types, and factor analyses of species associations. Although these analyses were generally concordant, they enabled only crude segregation of fishes by habitat niche, namely rheophilic, limnophilic, or generalized. These analyses also showed that fish species were largely independent of each other in their habitat use at smaller spatial resolutions (quadrat-level) and moderately large spatial extents (stream reaches of three to five meander sequences). Hence, pooling of quadrat-abundance data for fishes into several mesohabitat types (e.g., shallow-pool vs. fast-riffle), or consideration of mean habitat use for fish species over all quadrats (e.g., for depth and velocity) will allow more efficient and accurate delineation of habitat-use guilds. These analyses also suggest that abundant fish species do not differ from rarer species in variability of occurrence across spatiotemporal samples.