ABSTRACT
The use of fish communities as indicators of biological integrity was documented as early as the turn of the century on the Illinois River. Fish have been and remain a major part of any aquatic study designed to evaluate water quality. Not only are fish a highly visible component of the aquatic resource, but they are one component that is easily sampled by professional biologists. This chapter discusses the evaluation of fundamental considerations of biological integrity at multiple hierarchical levels of ecosystem integration. Focus on biological evaluations enables integration of water-body change, since living systems assimilate the range of site-specific biotic and abiotic conditions. Karr et al. suggest that narrow chemical criteria assume declining water resource conditions have only been caused by chemical contamination. Water quality standards contain rules that define minimum stream flows above which chemical and narrative criteria must be met.
