Mercury levels measured in some fish caught in a Calaveras County lake about 30 miles northeast of Stockton have prompted a state advisory.
Sam Delson is with the state Office of Environmental Health Hazard Assessment, which is part of the California Environmental Protection Agency. He says women younger than 46 and children younger than 18 should not eat the fish at all because it has high levels of mercury.
"We don't have information on specifically what caused it in that lake," says Delson. "There are a variety of sources of mercury, sometimes from older mining operations. There are also issues from atmospheric deposition - there's mercury in the air."
Mercury poisoning can damage the brain and nervous system.
Delson says men and older women can eat black bass from the reservoir but should limit their consumption to one serving per week. The advisory is one of more than 80 in place for waterways throughout the state.