The fish are clearly exposed to cancer-causing agents, and at this point, we really don't know what chemicals are responsible. We suspect it's from (polluted) runoff.

In the South River we have not established a link between the tumors and PAH exposure.

We collected 30 fish from the South River near Annapolis last year. Sixteen fish had raised, pinkish red lesions around the mouth.

Since 1992, we have surveyed 10 other locations in the Chesapeake watershed. These catfish from the South River have the highest skin tumor rate and second highest liver tumor rate.