Contaminants measured in fish tissue include mercury, PCBs, and PFAS (perfluoroalkyl and polyfluoroalkyl substances). Mercury is widely distributed in the environment. Once mercury is deposited in water, certain microbes convert it into methylmercury, a highly toxic form that accumulates in fish. Check local fish advisories before eating fish from rivers and streams.

Where are fish tissue samples collected?

Crews capture fish throughout the
sample reach using methods
like electrofishing. Upstream Downstream

To learn more, see the
NRSA Field Operations Manual.