The various metrics that comprise the Puget Sound Lowland BIBI are based on several characteristics, or attributes, of the organisms included in the analysis. These attributes include whether or not the invertebrate is a predator, long-lived, and tolerant of pollution, as established by Bob Wisseman (1998), and whether or not the animal is a clinger, as defined by Merritt and Cummins (1996. An Introduction to the Aquatic Insects of North America, Kendall/Hunt Pub. Co.) Neither Wisseman’s nor Merritt and Cummins’s list is comprehensive; however, they represent an established precedent that was used in the calibration of the BIBI.
It is not always practical or even feasible to uniquely identify benthic macroinvertebrates that have similar phenotypes (appearances) during their aquatic life stages. Therefore, some macroinvertebrates are identified to a taxonomic level that is higher than Genus or Species, such as Family or Order. However, in other cases the organisms can be positively identified as belonging to a select subset of Genera; therefore, these organisms can be identified at a custom taxa level that is in between the standard taxa hierarchy. These custom taxa levels are indicated with a “Group” (e.g., Rhyacophila Angelita Group) or a “Complex” (e.g., Orthocladius Complex) designation, or they can be designated with a slash (e.g., Kogotus/Rickera). Some examples of these custom taxa levels are included in the attribute table below.