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How are these data used?

Observations are used to determine values for four physical habitat indicators.

Physical Indicators

A rock ledge in a stream, an example of suitable fish habitat. Photo by EPA

In-stream habitat measures the complexity of habitat providing cover for fish and other organisms within the stream and its banks. Cover features include large woody snags, boulders, rock ledges, undercut banks, overhanging vegetation, brush and tree roots. Channelizing streams, hardening shorelines, and removing vegetation and snags can result in habitat loss.

Where is in-stream fish habitat observed?

Crews observe and record characteristics
of fish habitat throughout
the sample reach.
Schematic of stream segment showing 11 evenly spaced transects.

To learn more, see the
NRSA Field Operations Manual.