[Water_news] 4. DWR'S CALIFORNIA WATER NEWS -WATER QUALITY-5/28/09

Department of Water Resources

California Water News

A daily compilation of significant news articles and comment

 

May 28, 2009

 

4. Water Quality –

 

High levels of mercury in Lake Piru bass, study shows

The Ventura County Star – 5/27/09

By Zeke Barlow

 

An examination of pollutants in 152 California lakes found that largemouth bass in Lake Piru have levels of methylmercury that could make it unhealthy for women and children to eat.

 

Although further study is needed before a health advisory is issued for the lake, the initial results showed the largemouth bass, which often have high levels of mercury, were above the threshold for safe consumption levels.

 

Fish from Lake Casitas were tested but did not have high levels of mercury.

 

“There is definitely a concern,” said Jay Davis, a senior scientist with the San Francisco Estuary Institute, which did the study for the California Water Resource Control Board. “We don’t want to send the message that people shouldn’t eat fish or be fishing. It’s more that they should try to be informed and try to focus on the fish that have a lower level of the contaminants.”

 

The bass at Lake Piru are not alone in having high concentrations of pollutants.

 

Only 15 percent of the lakes that were sampled were determined to be “clean,” meaning the fish had levels of mercury, PCBs, DDT and other pollutants that were all below the limit at which officials establish health advisories, according to the report — “Contaminants in Fish from California Lakes and Reservoirs.”

 

Mercury levels over .44 parts per million in fish is considered unhealthy for women and children to consume. The largemouth bass in Lake Piru tested at .46 parts per million.

 

Methylmercury — a by-product from gold mining that was rampant in the state more than a century ago — was the main culprit. Of the lakes sampled, 74 percent had levels of mercury high enough to be considered unhealthy to eat more than three servings a week. Overall, 26 percent had even higher levels of mercury — considered unhealthy to eat at all by women and children.

 

Much more comprehensive tests of different species would have to be done before the Office of Environmental Health Hazard Assessment issues an official warning against eating fish. Even if a fish, such as bass, is deemed unhealthy, other fish from the same lake further down the food chain are OK to eat. Brown bullhead from Lake Piru were also tested but had low levels of mercury, the study found.

 

Swimming in the lakes or other recreational activities are still safe, officials added.

 

In Northern California, where gold mining was much more prevalent historically, mercury was known to be a problem, but this is the first time the southern half of the state showed widespread problems, too, Davis said.

 

“It was somewhat surprising to see some lakes in Southern California with high concentrations,” he said.

 

It was news to United Water Conservation District, which stores water in Lake Piru to recharge the aquifers on the Oxnard Plain.

 

“This is the first sampling we know of,” said Dan Detmer, a hydrologist with the district. He said the district will look into the findings and potentially issue a warning if needed.

 

Detmer said some of the mercury contamination could be coming from the water the district gets from the Sierra Nevada, where there was a lot of gold mining. Mercury was used to extract gold and then dumped into the watershed where it accumulates in sediment and remains for decades.

 

Davis said mines around Southern California also could have contributed to the problem.

 

Fish at the top of the food chain, such as largemouth bass, tend to have higher concentrations of mercury because it is stored in the muscle.

 

Too much exposure to mercury can affect a human’s nervous system and women can pass on the pollutant to their fetuses.

 

Even if further tests show the bass in Lake Piru shouldn’t be eaten by children and women, some question the impact.

 

Most bass fishermen who come into Eric’ s Tackle Shop in Ventura are releasing the fish they land at Lake Piru, shop owner Eric Huff said.

 

“They are fishing for sport and not for food,” he said.

 

Clayton Strahan, a park ranger at the lake, said there aren’t any statistics on the number of fish caught and kept versus the number released. He estimates there are somewhere from 50,000 to 70,000 fishing trips per year at the lake, with many fishermen making return visits.

 

Dwayne Maxwell, a senior fisheries biologist with the California Department of Fish and Game, said many of the bass caught are released back into the lake — but a fair amount are eaten.

 

“A lot of people who fish in Southern California are subsistence fishermen,” he said. And even if a fish is deemed unsafe to eat, it doesn’t mean people are deterred.

 

“There have been signs up on the Cabrillo Pier (in San Pedro) cautioning people against eating white croaker, but that doesn’t keep them from taking them home by the bucketful,” Maxwell said.

 

These tests are the first in a long string of studies looking at the health of California waters. Next year, another round of tests will be done on lakes, followed by examinations of the pollutants in streams and the ocean.

 

If a water body is found to be very polluted, it could qualify for a federal cleanup of the waterway#

 

http://www.venturacountystar.com/news/2009/may/27/high-levels-of-mercury-in-lake-piru-bass-study/

 

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