Definitions for "Biological criteria"
numeric values or narrative expressions that describe the reference biological condition of aquatic communities inhabiting waters that have been given a designated aquatic life use.
Biological measures of the health of an environment, such as the incidence of cancer in benthic fish species. Biological criteria can consist of narrative statements (in the simplest case) or of numeric statements.
under the Clean Water Act, numerical values or narrative statements that define a desired biological condition for a waterbody and are part of the water quality standards.