Karen L. Smathers, Michael R. Mills, Ron E. Houp, and John F. Brumley, Kentucky Division of Water, 14 Reilly Road, Frankfort, KY 40601

Karr's (1981) original Index of Biotic Intergrity (IBI) was developed using third-order midwestern streams. In order to accurately assess fish communities in other areas, the IBI should be calibrated and/or modified to "fit" the region. One objective of Kentucky Division of Water's Reference Reach Program was to sample a number of least-impacted or reference sites within all ecoregions in Kentucky, and then to use the data obtained to adapt the metrics of the IBI for each ecoregion. Forty reference reach sites were established across the state and were sampled twice yearly between 1992 and 1995. Twenty-six of the sites were in the Interior Plateau or Western Allegheny ecoregions. Metrics were calibrated for headwater and wadable streams in the Interior Plateau and Western Allegheny ecoregions using methods outlined by Karr et al. 1986, Ohio EPA 1987 and Simon 1991. Maximum species richness lines were developed for nearly all metrics in order to determine the 5, 3, and 1 scoring criteria. Some new metrics were found to be more effective than the original ones when calculating an IBI at headwater sites. Several original metrics were modified for use at wadable sites.