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DHS news release

April 22, 2004

Contact: Bonnie Widerburg (503) 731-4180
Technical Contacts: Ken Kauffman or Dave Stone, DHS (503) 731-4012; Scot Kruger, Lane County Environmental Health (541) 682-3753

Elevated levels of mercury in sport-caught fish from Dorena Reservoir in Lane County


The Oregon Department of Human Services (DHS), in cooperation with Lane County Health Department, is advising the public today of increased levels of mercury in fish caught from Dorena Reservoir.

The advisory recommends specific limits on the amount of fish eaten from this reservoir.

Dorena Reservoir has been under a mercury advisory since February, 1997 and today’s advisory is a modification of the initial advisory. Increased levels of mercury in the fish are documented by Oregon Department of Environmental Quality (DEQ) laboratory testing of largemouth bass taken from the reservoir in 2003. The average mercury level for all fish sampled from Dorena Reservoir since 1993 has risen from 0.37 ppm (parts per million) in 1997 to 0.45 ppm in 2003. DHS generally issues mercury advisories when average mercury levels reach or exceed 0.35 ppm in fish tissue.

The newly recommended limits for consumption of fish from Dorena Reservoir are as follows:

  • Children six years of age and younger should not eat more than one 4-ounce meal every two months;
  • Women of childbearing age, including pregnant women and breast-feeding mothers, should not eat more than one 8-ounce meal per month;

  • Women beyond the age of childbearing, children six years of age and older and other healthy adults should not eat more than one 8-ounce meal every two weeks.
The source of mercury in Dorena Reservoir is believed to be natural volcanic rocks and minerals and geothermal activities in the upper drainage areas. The movement of mercury into waterways and the bioaccumulation of mercury in fish may be influenced by past mining practices in the watershed, but this subject is not well studied.

Once mercury enters the food chain, it is not likely to diminish or disappear from fish and other organisms living in the reservoir. The Oregon DHS, DEQ and Department of Fish and Wildlife continue to monitor contaminant levels and will update the advisory if significant changes occur.

Anglers are encouraged to practice catch-and-release fishing, especially for larger specimens of any species, because older and larger fish have greater accumulations of mercury in their tissues. In Dorena Reservoir, as in most other waterbodies in Oregon, bass have higher levels of mercury than most other species. Because mercury is bound to the muscle tissue of fish, exposure to consumers cannot be significantly reduced by cleaning, cooking, brining, smoking, canning or any other known preparation techniques.

Fish is known to be an excellent source of nutrients for people of all ages, and DHS encourages fishing and eating of fish from Dorena Reservoir as long as consumption does not exceed the levels recommended in this advisory.

Note: This advisory is similar to the advisory in place for the entire mainstem of the Willamette River, but the average mercury level in fish from Dorena Reservoir is somewhat higher than that of the river.