Researchers believe the toxic form of Pfiesteria lasts for just a matter of hours, Vogelbein said. States that close rivers after finding the lesions, then, would be acting after the fact. Sales of Chesapeake Bay fish and shellfish fell off sharply last year amid wide publicity of Pfiesteria problems. Maryland and Virginia closed the Pocomoke River after watermen working on the river became sick and Pfiesteria was blamed for killing fish. There is no evidence that eating fish from waters where Pfiesteria is found causes illness.
Health problems stem from the release of toxins into water.
Vogelbein studied fish that developed sores this year and last year. His findings are similar to those of Vicki Blazer, a fish pathologist for the U.S. Geological Survey, which were reported Sept. 30. The USGS study included fish with lesions from three Eastern Shore rivers that were closed last year and showed fungus caused almost all the sores. Michael Mac, fisheries program director for the USGS, said the lesions shouldn't be used as an indicator of Pfiesteria . Deborah Kallgren, spokeswoman for the Virginia Department of Health, said the work by Vogelbein, Burkholder and the USGS will be discussed at a November meeting of the Pfiesteria task force.