Evaluating four fish-based indices of biotic integrity for similar measures of ecological condition

While the use and development of biological indices for management and planning purposes has increased in popularity over the past few decades, many of their properties are rarely evaluated. Using stream fish community data from numerous watersheds across several management jurisdictions, this study compared and evaluated four different indices of biotic integrity to assess their use in biomonitoring programs. With multivariate comparisons, statistical resampling and species replacements, sensitivities of indices to changes in community composition were examined. While indices were positively correlated at a large scale, different relationships among indices were found across the spatial regions represented by management jurisdictions. Indices responded differently to replacements of native with non-native species as well as year-to-year changes in community composition (i.e., species turnover). Variability generated through bootstrap resampling showed the potential to change resulting scores up to a value of 50, altering stream health designations that are commonly used in decision-making. The differences in index scoring seen due to differences in the four calculations prevent largescale comparisons and integrated management from taking place across management jurisdictions. This paper emphasizes that the potential advantages and limitations of indices of biotic integrity must be considered when developing/choosing one for use in a given region.