Assemblage and Community Parameters

Species abundance curves These plot the relative abundance of species, ranking from most to least abundant (Newman 1995, pp. 285). These measurements may be most useful in a comparative mode, as the rankings and distribution change over time. 

Species richness, diversity, and equability Perhaps the most commonly measured aspects of communities has been the number of species, evenness of the composition, and diversity. These measures are not measures of toxicant stress, but do describe the communities. Prior judgment as to the depletion of diversity relative to a comparative site 

Many tools exist for measuring the number and evenness of the species distribution. All are summary statistics generating one number to condense the information on richness, diversity, or equability. Often these measurements are used to describe the so-called healthy or unhealthy systems without regard for the limitations of the measurements or the absurdity of the health metaphor. A review of these methods can be found in R. A. Matthews et al. (1998). A major disadvantage is that these summary statistics compress a great deal of information into a single number, thereby losing most of the valuable information contained in the dataset. 

Total number of fish species3 (native fish spedes)b Expectations for metrics 

Number and identity of darter species (benthic species) 

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