MERCURY CONCENTRATIONS IN FISH TISSUE, RUSSIAN RIVER, NORTHERN CALIFORNIA

The work was conducted as part of The Waterkeeper Alliance & UNC- Asheville's Mercury in Fish Project in 2004. Five smallmouth bass were caught in the river at the SCWA Wohler dam near Forestville and one largemouth bass in a near-by former gravel pit adjacent to the river in July 2004. The fish ranged from a 155 gram one year-old to a 556 gram 3 year-old. Fish were caught by angling and placed whole in sterile bags on ice. Fish were sent overnight to UNC- Asheville's lab for analysis using EPA standard methods.

The concentrations of mercury in Russian River bass ranged from 0.364 to 0.702 ppm wet (mg/Kg). This is similar to concentrations in the 1997 SF Bay Institute study that included 12 Striped Bass with a mean of 0.42 ppm wet, and the 1999 USGS Gold Mining Region study with 14 lake caught smallmouth bass with a 0.63 mean and 20 stream caught Brown Trout with a mean of 0.12 ppm. EPA health advisory limit on fish is 0.30 ppm and the SF Bay Regional Water Board uses a 0.14 ppm advisory limit.

The watershed upstream of the fish study contains a minimum of 24 abandoned mercury mines and the Geysers Steamfields Complex with unknown additional local sources and unknown atmospheric sources. Excess nutrients from agriculture and urban stormwater depressing oxygen levels and millions of pounds of sulfur applied to Russian River vineyards increasing populations of the bacteria that convert inorganic mercury are likely significant factors.