Study: Most key fishing spots in state polluted ENVIRONMENT

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The most comprehensive survey ever of pollutants in California's lakes and reservoirs has found that only a few of the most popular fishing spots are free of mercury, PCBs and other contaminants.

Of 152 lakes tested statewide, 21 were clean while 131 showed one or more pollutants at levels above state health guidelines, according to the study released Monday by the State Water Resources Control Board.

In Northern California, some of the cleanest were the high-elevation lakes of the Sierra Nevada and the Trinity Alps. The only Bay Area body of water free of contaminants found was Lago Los Osos in Quarry Lakes Regional Recreation Area in Fremont, where fishing isn't allowed.

"This study is helping to define the scope of the statewide problem of contaminants accumulating in sport fish," said Jay Davis, lead author and toxicologist at the nonprofit San Francisco Estuary Institute in Oakland.

Results of the two-year study of California lakes, rivers, reservoirs and coastal waters will be used to develop cleanup plans in watersheds that feed the lakes and to establish guidelines for consuming fish to protect anglers and their families from health risks, Davis said.

In addition to the 100 popular lakes tested in 2007, the survey included 50 other lakes picked at random. Next year, 2008 sampling results from 100 additional lakes will be released, bringing the total to 250 lakes out of 9,000 in California. Some 12,000 fish are being collected and tested, including bass, trout, catfish and carp.

Popular lakes were those that appeared in fishing guides and were known to state fish and water officials. The lakes were considered clean if all concentrations of pollutants in all the tested species were below thresholds set by the state.

Toxic chemicals under scrutiny were mercury, most of which comes from past mining activities; PCBs, chemicals once used in electrical equipment; and the banned pesticides DDT, dieldrin and chlordane. Fish were also tested for selenium, which is discharged as waste from oil refineries and seeps from irrigated land in the Central Valley.

Methylmercury, the potent form of mercury that taints fish, is the most widespread potential health risk, the study said.

Inorganic mercury, used as an ingredient in gold mining or washing out of crushed rock and natural rock formations, transforms to methylmercury in rivers and lakes, where it accumulates in ever-higher concentrations as it moves up the food chain to larger fish-eating species, such as large-mouth bass.

About one-fourth of the lakes surveyed had at least one fish species with a mercury level high enough that state health officials would consider prohibiting it for the most sensitive humans - pregnant and nursing women, women between 18 and 45 years old who might conceive and children.

PCBs, or polychlorinated biphenyls, are the chemicals that caused the second-most concern among health officials. In Northern California, more than one-third of the lakes had a fish species with a concentration about the state's threshold.

Concentrations of banned pesticides and selenium were generally low, and they infrequently exceeded the state's thresholds, the study said.

The study will be used to identify the lakes where state health officials should return to gather and test more fish and establish safe-eating guidelines, officials said.

The strictest limits will be set for pregnant and nursing women because they can pass pollutants onto fetuses and infants, who are most vulnerable to poisons. Mercury and PCBs can impair mental and motor development, while PCBs and the pesticides are believed to increase cancer risks.

Curtis Knight, Mount Shasta manager for California Trout, a 7,500-member conservation organization, said the new information is important for knowing which fish are safe to eat.

"A big part of fishing in a lake is fishing with your kids. That's how they learn to fish. You certainly want to know what you're feeding your kids, and you want that to be safe," Knight said.

Knight said the lakes and the fish in them are indicators of watershed health. "Lakes are collecting bodies for what's coming out of the streams, and that gives a sense of the watershed's history," he said.

Online resources

Read the report at links.sfgate.com/ZGZG.

Read the state's guidelines at links.sfgate.com/ZGZH.