Editor's note: This is the fourth in an occasional series of stories by Post-Bulletin reporter John Weiss as he monitors the Zumbro River at Oxbow Park, north of Byron. The stories follow the series "Web of Water," published Dec. 14, 2002, which looked at the overall health of surface water in southeastern Minnesota.
Through the slightly stained water of the Zumbro River, I could see the fish on my line -- a smallmouth bass?
No, please, not a smallie, I said to Bill Denny.
Then I saw the forked tail.
Yes! A sucker. Just what I was fishing for.
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Denny has lived along the river about two miles downriver of Oxbow Park for 43 years. He and I were fishing for suckers or carp because he likes to smoke them for eating. But after reading about all the pollution in the region's rivers, he asked whether he should continue to eat those fish.
What should he and his family do?
Eat the fish. But take some precautions, according to the Minnesota Department of Health.
In the case of streams and lakes away from the Mississippi River, the most common pollutants are things such as fecal coliform from sources along the stream and mercury from miles or continents away.
Patricia McCann, a research scientist with the Minnesota Department of Health and a leader on fish consumption warnings, said coliform is killed if the fish is handled and cooked properly. It's mostly on the outside, so filleting the fish and cooking it gets rid of any fecal material. Smoking also should kill harmful things if the fish are smoked long enough, she said.
When it comes to mercury, however, we're out of luck. It gets directly into the meat and can't be cooked out. Improving watersheds won't help because most mercury comes from power plants perhaps half a world away, carried on the planet's atmosphere, McCann said.
The trend in mercury has stabilized, she said.
Another question is the Mississippi River and polychlorinated biphenyls. PCBs are an industrial chemical of great use in electrical transformers. If PCBs get into the water, they can cause cancer or other health problems.
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The PCBs love fat and accumulate in small bugs on the bottom of stream beds. Small fish eat the bugs, big fish eat the small fish. People eat the big fish.
PCB amounts gradually have declined, but people still remember the bad old days of 20 years ago and don't eat fish from the river. I love to eat fish from the river and have no fears of PCBs. But I stick with smaller fish and avoid those that feed off the bottom, such as catfish.
As we fished the Zumbro River together in the cool shade of a maple tree, Denny said fishing was once really good on the river.
"You could catch walleye, northern, crappies, the river had it," he said. A manure spill from a slurry tank, however, killed many fish about 20 years ago. The Department of Natural Resources said fish would come back, he said, but "it never come back, it's been a long time."
There was a time when he and his family could see things 8 feet down in the water. Then algae came in, and visibility dropped.
In one way, Denny thinks the Zumbro is cleaner now because farmers aren't letting cattle graze in it. Then again, farmers are using more chemicals that get into the water.
The question of whether he would smoke a fish caught that day was moot -- I was the only one to catch a sucker. It weighed about 21⁄2; pounds, and I gave it to Oxbow Park to feed to the otters.
www.health.state.mn.us
