Modification and assessment of an index of biotic integrity to quantify water resource quality in great rivers

Abstract

Abstract A measure of stream quality, the index of biotic integrity (IBI), was adapted to great rivers (>3226 km 2 ) and calibrated using a variety of spatial scales. Fish fauna was sampled at 60 localities within 15 impoundments of the Ohio River drainage, eastern Ohio, West Virginia and Pennsylvania, with boat electroshocker methods during the summers and autumns of 1990–1993 to provide biological information for the IBI. Significant correlation was not found between ecoregion or differing reservoirs; however, the IBI was sensitive to differences in land use and variable industrial and municipal loadings. Species richness, the percentage large river faunal group, the proportion of round‐bodied sucker species, the number of centrarchid species, the number of sensitive taxa and the proportion of simple lithophilous spawning species showed the greatest change between riverine and lacustrine habitats within an impoundment. The percentage large river faunal group metric was not significantly different between riverine, transitional and lacustrine habitats; however, the metric reflected significant differences when evaluated with habitat information. The number of centrarchid species was higher in lacustrine habitats, whereas round‐bodied sucker species were highest in transitional habitats. The inherent variation of proportional metrics was significantly reduced with the removal of gizzard shad. This modification of the IBI will enhance assessment sensitivity over the original approach designed for wadable streams and rivers.