Biological monitoring is performed on many streams throughout the Commonwealth for a variety of reasons.  Fish, macroinvertebrate and algae data from the ambient stations provide long-term and trend information on mainstem rivers and many major tributaries. These stations will be revisited every five years.  Most of the ambient biological stations are located on streams that also have water quality monitoring.  This information is used to help in the compilation of the 305b Water Quality Report to Congress.  Intensive surveys may also be performed on areas previously unmonitored in order to determine waterbody usages, effects of point and nonpoint source pollution or background conditions within a drainage.

Streams are assessed by using a combination of multiple factors.  The three assemblage combination of fish, macroinvertebrates and algae are most often used in conjunction with habitat assessments, but can also be combined with information from bacteriology and physicochemical results to give a complete picture of the health of a stream.  The watershed biological monitoring group is also responsible for collecting fish samples for fish tissue analysis.  For more information about our collection methods please go to the Standard Operating Procedures page and view Methods for Assessing Biological Integrity of Surface Waters.