Effects of water quality and habitat on composition of fish communities in the Upper Colorado River Basin

The sampling design of the National Water-Quality Assessment (NAWQA) program emphasizes a multidisciplinary approach using physical, chemical, and biological information to provide multiple lines of evidence to describe water-quality conditions. The composition of fish communities at stream sites representing selected environmental settings is one characteristic assessed as part of the NAWQA program (Meador and others, 1993a). The presence and abundance of fish species can be related to water chemistry, physical habitat, and land-use activities to provide a more complete picture of water quality across a river basin. Although fish communities may have a high degree of natural variability, they can be useful indicators of ecosystem health (Moyle, 1994). Berkman and others (1986) recommended fish be given consideration in biological water-quality monitoring of streams because they generally are perceived by the public to be ecologically relevant, and they are directly related to legisla