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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 Co.Environmental Health, (541) 682-3753

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


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

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

Cottage Grove Reservoir was the first body of water in Oregon to be placed under a public health advisory because of mercury contamination found in fish. In April, 1979, Lane County Health Department, in consultation with the Oregon Health Division, issued a public health advisory suggesting limits on the amount of fish to be eaten from the reservoir.

Since that time there has been additional testing of fish, most recently an Oregon Department of Environmental (DEQ) sampling survey performed in 2003. These tests show the average level of mercury in fish from the reservoir to be 0.58 ppm (parts per million), which is higher than the average level (0.53 ppm) documented up to 1994. Bass tested in the most recent survey had an average mercury level of 1.6 ppm. DHS generally issues mercury advisories when the average mercury level in fish from a waterbody reaches or exceeds 0.35 ppm.

The newly recommended limits for consumption of fish from Cottage Grove Reservoir are:

•Women of childbearing age, particularly pregnant or breastfeeding women, children under six years of age and persons having liver or kidney ailments should avoid eating any fish from this reservoir:

•Healthy women beyond childbearing age, other healthy adults and healthy children six years of age and older should eat no more than one 8-ounce meal per month.

The source of mercury in Cottage Grove Reservoir appears to be natural volcanic rock and minerals, and geothermal activity 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 or well understood.

Once mercury enters the food chain it is not likely to diminish or disappear from fish and other organisms living in the reservoir. 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. At Cottage Grove Reservoir, large bass have the highest levels of mercury. Because mercury is bound to muscle tissue in fish, exposure to consumers cannot be significantly reduced by cleaning, cooking, brining, smoking, canning or by any other known preparation techniques.

Fish is known to be an excellent source of nutrients, and DHS encourages fishing and eating of fish from Cottage Grove Reservoir by healthy adults as long as the consumption limits in this advisory are not exceeded.

Note: This advisory is similar to the mercury advisory in place for the entire Willamette River mainstem, but the levels of mercury from fish in the river are not as high as those from this reservoir.