Relationships Among Biotic Indices and Their Responses to Ecological Gradients in Least-Disturbed Ozark Streams

Biotic indices are quantitative tools used to infer stream health. Because they need to be tailored to a specific faunal group (fish or aquatic invertebrates) for similar stream sizes and regions, many indices have been created. Therefore, understanding the consistency among index interpretations within and across faunal groups is needed. Investigating these differences may shed light on the consistency and limitations of individual indices and help managers select an index that will most accurately portray environmental conditions. We compared three fish (Index of Biotic Integrity, species richness, and percent intolerant individuals) and three invertebrate indices (Hilsenhoff Biotic Index, taxa richness, and Ephemeroptera, Plecoptera, and Trichoptera richness) using spearman’s rank correlation in the Ozark National Scenic Riverways (ONSR; n=24) and the Buffalo National River (BNR; n=31). Overall, relatedness in indices were highly variable (ONSR r=-0.04-0.81, p=0.84-<0.01; BNR r<0.01-0.87, p=0.98-<0.01) and differed by river system, watershed area, and water temperature.  Because of the inconsistency among indices, managers may need to consider their objectives and that these indices may be related to factors other than degradation (e.g., watershed area) to best determine the most appropriate stream health index to meet their goals.