An index of biotic integrity (IBI) developed for fish in the South Platte River Basin (Schrader, 1989) can be used as a biological indicator of habitat and water-quality conditions. An IBI for a site was calculated by summing the ranks of three categories of fish-community characteristics; the number and types of fish, fish feeding habits, and fish abundance and health. The ranks were determined by comparing a fish-community characteristic at a site to those expected under natural conditions. The site scores were then grouped into three classes; significantly degraded, moderately degraded, and minimally degraded.

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