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In the past two weeks, she’s spotted hundreds of smaller dead fish and about 50 larger dead fish, she said.
The fish kill has led Schmidt and several other residents to question the health of the popular swimming hole — especially after the lake tested positive for a number of pollutants after last year’s flood.
Goodview officials, however, say there’s nothing to worry about and blame the fish die-offs on a harsh winter that depleted the lake’s oxygen content.
Post-flood testing for pollutants — including petroleum, total coliform and E. coli — show contamination has dissipated, said Mayor Jack Weimerskirch. The lake will be sampled again before swimming season, he said.
“We attribute it to the winterkills, which is pretty much a normal, natural thing every year,” said Greg Volkart, Goodview’s public works director who oversees the maintenance of Lake Goodview and Michael LaCanne Memorial Park. “It was a hard winter with lots of snow cover and ice. That lowers the lake’s oxygen content.”
Milder winters over the past six to eight years caused few, if any, winter fish die-offs at Lake Goodview, Volkart said, which may explain why residents are particularly concerned this spring. With the recent ice breaking and appearance of dead fish, city staff has taken a couple of calls from concerned residents who’ve noticed a higher number of dead fish along the shores, he said.
The die-offs aren’t limited to southern Minnesota.
Severe winterkills have been a common sight and smell this year for many lakes and ponds throughout the state. It’s caused the Minnesota Department of Natural Resources to open 31 water bodies for unlimited fishing.
In southern Minnesota, shallower eutrophic water bodies — which include lakes that become rich in dissolved nutrients, especially phosphates — are more prone to winterkill, said Dan Dieterman, DNR assistant fisheries supervisor in Lake City.
High levels of phosphorus and nitrogen in land-locked water bodies such as Lake Goodview and Lake Bartlett grow thick, aquatic plants, Dieterman said.
When snow and ice cover the lake, it limits photosynthesis, and plants decompose, taking up more oxygen. The oxygen deficit kills a variety of more susceptible fish such as bluegill, bass, trout and gizzard shad, he said.
Lake City Area Fisheries hasn’t recorded any previous fish die-offs on Lake Goodview or any other local water bodies, but 2001 was the last largest winterkill in southern Minnesota, Dieterman said.
“It’s been exacerbated because of agricultural practices in the southern part of the state, but for hundreds of years it’s been a reoccurring event that happens during bigger winters,” Deiterman said.
According to water quality measures in 2007, Dieterman categorized Lake Goodview on the low side of eutrophication. That means nutrient levels for phosphorus and chlorophyll, 26 parts per billion and 12.4 ppb respectively, rated in the second highest level out of four stages.
The DNR plans to run water-quality analysis and fisheries assessment in Lake Goodview this year to compare post-flood measurements from last year, Dieterman said.
Cal Fremling, a retired Winona State University biologist who has studied the river for 48 years as a teacher, fisher, hunter, historian and writer, agreed the dead fish along Lake Goodview’s shores was related to winterkills, especially gizzard shad, a species of baitfish.
“They’re at the northern extent of their range here, and they can’t handle a long cold winter,” Fremling said.
Fish, like other animals, have antibodies against bacteria. The longer the winter, the fewer antibodies they have left to fight off bacteria and viruses, Fremling explained.
While winterkills aren’t unusual, Fremling related it to Lake Goodview becoming more enriched every year with algae blooms due to sediment and nutrients washing in from fertilized lawns.
And the flood gave the lake an extra jolt, he said.
“When I came to Winona in 1959, I swam in Lake Goodview often and it was crystal clear. It’s not crystal clear anymore,” he said. “It’s not surprising to me because of the increased development around it where people have lawns, gardens and all that kind of stuff.”
Contact reporter Amber Dulek at amber.dulek@lee.net or 507-453-3513.
