Assessing the ecological condition of the ohio river using a newly modified fish IBI

The Ohio River Fish Index (ORFIn) was developed in 2003 using data from 318 least disturbed sites. We’ve taken steps to refine the ORFIn by including a much larger data set (903 sites), moving from discrete scoring (1-3-5) to continuous scoring (0-100) and calibrating for natural, longitudinal changes in fish assemblage. Instream measure of substrate composition, fish cover and depth were recorded at each site allowing us to evaluate a total of 120 habitat metrics. We have now identified five discrete classes of habitat within the Ohio River mainstem and assign one of six fish quality scores (v.poor-poor-fair-good-v.good-excellent) based on statistical thresholds (5^th-25^th-50^th-75^th-95^th percentiles) derived from the distribution of ORFIn scores within each of the five habitat classes. By accounting for shifts in fish community expectations based on position within the river and habitat, we are better able to discern condition changes due to poor water quality.