REFINED BIOLOGICAL CLASSIFICATION FOR DERIVING BIOCRITERIA IN THE WESTERN ALLEGHENY PLATEAU ECOREGION: FISH ASSEMBLAGE RESULTS

We explored development of a refined aquatic life classification system for the Western Allegheny Plateau (WAP) ecoregion in Ohio considering potential geographic constructs (e.g., level IV ecoregions) and natural abiotic variables including geomorphic measures. First, we compared fish assemblage data across several hundred historical sites in the WAP ecoregion using Bray-Curtis similarity indices to test the classification strength of geographic constructs, i.e., do fish assemblages vary more within regions than between regions. We constructed alternate geographic groupings using stream basins, latitude, longitude, a random selection, and the results of a cluster analysis that used the biological assemblages to distinguish groups. There were statistical differences among some of the geographical regions; however indicator species analyses indicated that most differences were related to species replacements that would have little consequence on Indices of Biological Integrity, (IBIs) used to assess stream condition. We then explored fish assemblages in response to a suite of abiotic variables (reduced using PCA from a larger set of variables) using CCA analyses. Variables that reflect stream size, stream gradient, and landuse explained significant variation in fish assemblages. Stream size is already a part of the IBI index calibration, and landuse is reflected in the tiered aquatic life uses in Ohio. Stream gradient, however, is not currently a source of variation used in the calibration or application of the IBI. Current analyses are ongoing with new data including geomorphic variables, such as a Rapid Geomorphic Assessment (RGA), not available in the historical data.