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The Minnesota Department of Health (MDH) tests for mercury and other toxins in Minnesota waters and sets guidelines for the safe consumption of fish. According to Pat McCann, an environmental scientist at the MDH, the North Fork of the Crow River has been added to its Minnesota Fish Consumption Advisory. But, based on data from fish tested just east of Manannah, only the segment of the river from Lake Koronis to the border of Wright County (the part of the river that runs primarily through Meeker County) has been added to the list of impaired/threatened waters.

The fish consumption advisory recommends that pregnant women, women who could become pregnant, and children under 15 should eat these fish from the North Fork Crow River no more than once a week: channel catfish, up to 15 inches; and northern pike, 15-20 inches; and should eat these fish no more than once a month: carp, 15-25 inches; channel catfish, 15-20 inches; smallmouth bass, up to 20 inches; and walleye, up to 25 inches.

The general population should eat these fish no more than once a week: carp, 15-25 inches; channel catfish, 15-25 inches; northern pike, 15 to 20 inches; smallmouth bass, up to 20 inches; and walleye, up to 25 inches.

Mercury - the silver liquid found in thermometers and in some types of light bulbs - is an element that is found naturally in the environment and is released into the air primarily in the emissions from coal-burning power plants, according to the MDH. Mercury in the air isn't considered harmful because it's found in very small amounts, but as mercury is carried by rain or snow into water, it becomes methylmercury, which is highly toxic.

Fish become contaminated with methylmercury by eating foods (plants and smaller fish) that have absorbed the poison. Large fish can have very high levels of methylmercury. Humans and other animals ingest the toxin when they eat con- taminated fish.

According to the United States Environmental Protection Agency, methylmercury exposure can damage the senses and the brain in healthy adults.

Developing fetuses and children under 15 can be severely harmed by even small amounts of methylmercury because it can affect the developing brain and nervous system. For this reason, fish consumption advisories are more rigid for pregnant women and children than for the general public.

Unfortunately, according to Ned Brooks, the MPCA's mercury reduction coordinator, there is no way to remove mercury from the water. Since emissions from power plants are the primary source for mercury, most of it comes from other parts of the country, some of it from overseas.

The only way to fix the problem would be to tighten environmental laws that regulate the amount of mercury that can be released into the atmosphere, he said. As emissions become cleaner, rivers and streams should be able to recover.

McCann said that most of Minnesota's rivers and streams have some amount of mercury in them. Many waters haven't been added to the lists simply because they haven't been tested yet. However, she doesn't want people to panic and quit eating fish altogether, just to follow the guidelines and consume fish wisely.

The MPCA list was last published in 1998. This year 500 Minnesota waterways were added to the list of impaired/endangered waters while only four were taken off.

Lake Koronis and Rice Lake also have fish consumption guidelines because of mercury.

For more information or for a copy of the Minnesota Fish Consumption Advisory, either call the Minnesota Department of Health at 651-215-5800 or go online to www.health.mn.us.