Biological Conditions

The health of fish and macroinvertebrate (i.e., animals without backbones that are larger than the size of a pencil dot) communities is a strong indication of overall stream health.

Since the mid–1990’s many natural resources professionals working in the Anacostia watershed have monitored these communities using an Index of Biotic Integrity or IBI approach. The IBI compares the fish and macroinvertebrate communities of urban streams with those of healthy reference streams, incorporating geographical, ecosystem, community, and population, as well as distribution and abundance variables that account for differences in waterbody size, type, and region of occurrence.

Biological Characteristics: The macroinvertebrate IBI data put the overall health of the Sligo Creek subwatershed in the poor range. While the fish IBI data put the health of the subwatershed in the fair to poor range. There are also a number of fish barriers preventing fish from moving upstream.

Click on the following links for graphs showing biological conditions in the Sligo Creek subwatershed.

The adjusted Fish IBI score puts the overall health of the Sligo Creek subwatershed fish community in the Fair to Poor range.

The adjusted Macroinvertebrate IBI score puts the overall health of the Sligo Creek subwatershed macroinvertebrate community in the Poor range.

Sligo Creek also has a number of Fish Barriers that prevent fish from moving upstream. This is particularly a problem for migratory species.