California Delta Smallies Have Too Much Mercury
It was formed 18,000 years ago and modified by man as described here:
The Sacramento-San Joaquin Delta was formed about 18,000 years ago, when melting glaciers carved out and subsequently filled San Francisco Bay with water and northern rivers dragged debris and sediment from the Sierra toward the ocean, creating a huge swamp. Human activity in this wildlife-rich swamp did not cause significant damage until about 250 years ago. In the mid-1800s, Congress enacted reclamation laws, and by the turn of the century, miners with the help of Chinese laborers, had constructed small levees to hold back water, transforming the swamp into productive farmland. Source
A study was just completed by the State Water Resources Control Board of waterways in the state of California and it found that smallmouth bass and other fish in the Delta had the highest levels of mercury in the state.
The high mercury rate levels come from previous mining.
There have been numerous advisories posted regarding consuming large quantities of these fish and the warnings are often ignored.
But UC Davis researcher Fraser Shilling tells the Bee that some people ignore the advisories and nonetheless consume what they catch. Shilling surveyed people who fish rivers in Sacramento, Stockton and Suisun Bay about their catching and eating habits in 2008. He concluded that about 75,000 people consume enough fish from those areas to put them at risk, while about 8,500 eat about 10 times the amount that officials consider safe. Source
There are many of these types of environmental problems all over the country. There are many states where consumption of fish caught in contaminated waterways is limited or not recommended.
I would suggest pulling out the booklet provided by most fish and game commissions and read through the recommended limits for fish consumption if you are a catch and eat angler. You could be slowly causing brain damage with mercury or eating cancer-causing chemicals when you eat this fish or feed them to your friends and family.