California Sportfishing Protection Alliance
“Conserving California’s Fisheries"


More News

Your 501(c)(3) tax deductible cash donations are desperately needed if the fight for our fisheries is to continue. Read how you can donate!
Email Newsletter icon, E-mail Newsletter icon, Email List icon, E-mail List icon Enter your Email address to sign up 
for our Weekly Newsletter
For Email Marketing you can trust

More News


horizontal rule


85% of California's lakes polluted, some degree of risk eating fish


by Bill Jennings, Executive Director, CSPA

May 2, 2009 -- The State Water Resources Control Board's Surface Water Ambient Monitoring Program has released the initial results from the first year of a two-year screening survey of fish contamination in California's lakes.  The results reveal that the vast majority of lakes are severely polluted and pose some degree of risk to those who eat fish caught from them - only 15% of the lakes sampled were in the clean category.  The actual situation is likely worse because the study admits that many problems may have been missed due to the limited scope of the screening study.  The study monitored a limited group of pollutants and did not evaluate pollutant impacts to fish and wildlife.  The study can be found at: http://www.waterboards.ca.gov/water_issues/programs/swamp/lakes_study.shtml  

The first year of the Lakes Survey sampled some 150 lakes in 2007, including the most popular fishing lakes and reservoirs and random sampling of California's other 9,000 lakes to provide a statistical statewide assessment.  Next year, results from an additional 130 lakes that were sampled in 2008 will be available.

Fish tissue concentrations were evaluated using thresholds developed by the California Office of Environmental Health Hazard Assessment (OEHHA).  The study collected samples for methylmercury, PCBs, dieldrin, DDTs, chlordanes and selenium and focused on thresholds for human health fish consumption.  BDCPs (flame retardants) were also sampled but results were not available.  Unfortunately, the sampling did not encompass the vast majority of pollutants that pose threats to the environment and human health.  Nor did it evaluate impacts to fish and wildlife, which could be at risk from pollutant concentrations that are far lower than those that adversely affect people.

The survey employed two types of thresholds of concern.  Fish Contaminate Goals (FCG) are estimates of levels that pose no significant health risk to humans consuming fish at a rate of one serving per week.  These are based solely on public health considerations without regard for economic considerations or the benefits of fish consumption.  The other threshold is Advisory Tissue Levels (ATLs), which incorporate other factors including the potential health benefits from eating fish.

Twenty-six percent of the surveyed lakes contained fish with methylmercury levels above the FCG threshold: i.e., high enough to warrant recommending no consumption of the contaminated species for women between 18 and 45 years of age and children from 1 to 17 years of age.  Seventy-four percent of the lakes had a fish species with a methylmercury concentration level above the ATL threshold at which OEHHA would consider recommending consumption of less than three servings per week.  Generally, the highest methylmercury concentrations were found in bass in lakes below 2000 feet and the lowest concentrations were found in trout in lakes above 2000 feet.   Methylmercury concentrations were higher in northern California than southern California. 

Thirty-seven percent of the lakes contained fish species with an average PCB concentration above the OEHHA FCG threshold.  However, only one percent of the lakes had PCB concentrations high enough for OEHHA to consider absolute “no consumption” advisories.  Southern California had the highest PCB concentrations, with 60% above the FCG.   In northern California, 7% of high elevation lakes and 41% of lower elevation lakes exceeded the FCG for PCBs.

The other pollutants (dieldrin, DDT, chlordane and selenium) had fewer exceedances of OEHHA thresholds.  Dieldrin exceeded the FCG in 21% of lakes.  DDT exceeded the FCG in 17% of sampled lakes.  Chlordanes exceeded the FCG in 10% of lakes.  Selenium exceeded the ATL in 2% of sampled lakes.

Two findings are interesting.  First, very few California lakes containing predatory fish, such as largemouth bass, contain low concentrations of methylmercury.  Second, the low methylmercury concentrations found in the relatively “clean” lakes may be the result of high numbers of planted fish versus low self-sustaining populations.  Fish in lakes that cannot support self-sustaining populations have less opportunity to bioaccumulate pollutants.  For example, trout in Hetch Hetchy have high concentrations of methylmercury, perhaps because there have been no trout plantings for many years and the trout population is self-sustaining.

All in all, the report is a damning assessment of the state of California's lakes.  And, when subsequent assessments are conducted that sample for more constituents and go beyond considering only human health concerns to include potential impacts to fish and wildlife, the situation is likely to be far bleaker.


Polluted Lakes Map


On Fish Consumption


According to OEHHA, Advisory Tissue Levels (ATL) are safe if you consume no more than 3 meals a week.  Fish contaminate goals (FCG) are more stringent and are safe at one meal a week.  Concentrations above the FCG = no consumption for women, children and those compromised immune systems or, if even higher, no fish consumption, period.   For mercury: 26% of the lakes were above the FCG level meaining no consumption for women and children and 74% were above the level where OEHHA would consider recommending less than 3 meals a week.  These are not the same numbers.  For mercury: 26% of lakes = no consumption for women and children - 26% = no restrictions - 74% of lakes = levels that OEHHA would consider recommending less than 3 meals a week.  These are conservative standards and consuming fish within those limits should not result in any problems.