The San Francisco Chronicle
Michael Dougan Chronicle Staff Writer
December 05, 2000 — Seven popular species of sport fish in Tomales Bay should be consumed with caution — or not at all — because of elevated levels of mercury, Marin County health authorities warned yesterday.
The mercury levels are similar to those in fish from San Francisco Bay and pose a particular health threat to "the most sensitive" individuals — children and pregnant women — said Marin County Health Officer Fred Schwartz.
While the tidal waters of Tomales Bay have been so pure that is has supported the farming of oysters, clams and mussels since the 1920s, its water quality is being increasingly threatened from a variety of sources.
The mercury, in a particularly toxic form called methylmercury, was discovered in a test of Tomales Bay fish conducted in 1999 by the San Francisco Bay Regional Water Quality Control Board. Schwartz said it was the first time Tomales Bay sport fish had been tested for mercury.
The mercury is believed to have infiltrated Tomales Bay from an open-pit mercury mine located 6 miles upstream from 1968 to 1972. The mine is now an EPA Superfund site.
Leopard and brown smooth hound shark pulled from Tomales Bay have the highest levels of mercury and should not be eaten at all, Schwartz said.
In addition, he said, nobody should eat more than one meal a week of shiner or redtail surfperch, two meals a month of California halibut or Pacific angel shark and one meal a month of bat ray if the fish were caught in Tomales Bay. Those who eat one of those fish should avoid the others.
Commercially grown oysters, mussels and clams from Tomales Bay do not have elevated mercury levels and are safe to eat without restriction.
People who have been eating Tomales Bay fish without limitation are not likely to experience adverse health affects, he said. Schwartz described the warning as a conservative but prudent measure.
Simultaneous tests on Tomales Bay fish showed no hazardous levels of other toxic substances that were found in San Francisco Bay fish, including PCB, dioxin and organic pollutants.
Warning posters explaining recommended limitations on consumption of Tomales Bay sport fish will be posted in four languages in Marin and Sonoma counties, said Schwartz.
© 2000 The San Francisco Chronicle. via Bell&Howell Information and Learning Company; All Rights Reserved
