By Chris Schultz
March 1, 2004
Oxygen levels on Lake Ann have been tested
The DNR tested the oxygen levels on Lake Ann Tuesday, Feb. 24, with the readings going up, finding 3.9 mg/LD.O. near fish houses, and 5.0 east of the access, in the middle.
Below are the levels recorded by the DNR at numerous sites on Lake Ann.
Site 1 1 foot: 4.3 ppm; 5 feet: 3.6 ppm; 8 feet: 2.9 ppm; bottom at 9 feet.
Site 2 1 foot: 42. ppm; 5 feet: 4.2 ppm; 10 feet: 4.0 ppm; 13 feet: 2.4 ppm; bottom at 14 feet.
Site 3 1 foot: 4.6 ppm; 5 feet: 4.1 ppm; 10 feet: 5.4 ppm; 13 feet: 4.0 ppm; bottom at 14 feet.
Site 4 1 foot: 5.9 ppm; 5 feet: 5.4 ppm; 10 feet: 3.5 ppm; 15 feet: 1.0 ppm; bottom at 16 feet
Site 5 1 foot: 4.8 ppm; 5 feet: 4.6 ppm; 10 feet: 4.5 ppm; 14 feet: 0.5 ppm; bottom at 15.5 feet.
Site 6 1 foot: 4.3 ppm; 5 feet: 4.1 ppm; 10 feet: 3.5 ppm; 15 feet: 0.7 ppm; bottom at 16.5 feet.
Foe more information go to www.dnr.state.mn.us/areas/fisheries/montrose/index.html
Lake Ann intends to aerate
The Lake Ann Improvement Association is announcing their intent to put an open water aerator in the lake as early at Feb. 28, 2004, if the oxygen levels in the lake drop below 2 ppm.
Fish are severely stressed at oxygen levels below 2 ppm, and will struggle to survive.
Thus, the lake association is now working with the DNR to prepare to install an aerator on the northwest side of the lake in the oxygen levels continue to decline, and get below 2 ppm.
If aeration occurs, this will open a spot on the lake that could reach 1,000 feet wide.
The lake will be posted and the are itself will be marked.
This article serves as the first public notice regarding the intention of the lake association to aerate the lake.
It is believed that the latest stress on the lake and its fishery is still a repercussion from the flooding/high waters of the last two years, and the fact that vegetation in the lake was scarce last year (excluding the Curlyleaf pondweed).
Additionally, the heavy snow cover on the lake prevents sunlight from penetrating the ice allowing the vegetation to generate oxygen via photosynthesis.
‘Normal’ winter taking usual toll on fisheries
From the DNR
Anyone who has lived in Minnesota for more than a few years understands this winter is, historically speaking, a “normal” one. And during “normal” winters, some fish in southern Minnesota lakes die.
“Winterkill,” a natural phenomenon, occurs when dissolved oxygen in a lake drops to levels that cause fish to - basically - suffocate.
Lack of sunlight reaching aquatic vegetation due to snow cover, coupled with low water levels, can quickly make oxygen levels plummet.
“Southern Minnesota primarily has shallow lakes,” said Huon Newburg, Department of Natural Resources (DNR) Southern Region Fisheries Supervisor at New Ulm. “And many of those lakes are what we call ‘boom or bust’ lakes. They can provide a great fishery for a number of years but then suddenly ‘bust’ when conditions change.”
This winter has seen a considerable number of southern Minnesota lakes go bust due to prolonged snow cover and the fact that water levels are low as a result of near-drought conditions last year.
DNR Fisheries staff monitor lakes for oxygen levels and when it appears a winterkill is imminent, the lake is opened for liberalized fishing, Newburg explained.
“Under liberalized fishing, we basically allow people to take as many fish as they wish, in ways that are not usually allowed,” Newburg said. “If the fish are going to die anyhow, we’d like to have people make use of them first.”
Lakes open for liberalized fishing are listed on the DNR web site at dnr.state.mn.us.
To date, the DNR has opened a dozen lakes to liberalized fishing this winter, a considerably higher number than the past few years.
“Conditions have been ripe for winterkills, even though this has not been an unusually harsh winter.” “If you go back and look at historical winter weather conditions, this winter is pretty typical in terms of snow and temperatures,” Newburg noted. “What might be different, however, is that our shallow lakes are not as healthy as they once were and thus not able to withstand even normal winters as well as they once could.”
Consequently, “busts” occur more frequently today than they used to, at least on those lakes without aeration systems. And even aeration systems don’t always prevent “busts,” especially during severe winters.
As development and crop production continues unabated around southern Minnesota lakes, run-off into those basins continues to increase and impair water quality.
Additionally, many people still equate aquatic vegetation with “weeds” and attempt to remove it whenever possible, Newburg stated.
“Lakes have to have that aquatic vegetation if there is to be any hope for them to be healthy waters,” Newburg noted. “Removing those plants, both emergent and submergent, is nothing but bad news for fish, wildlife and water quality.”
With the advent of aeration systems some thirty years ago, the odds that a southern Minnesota lake could survive a typical winter without a winterkill improved considerably.
That has since been tempered somewhat by the degradation of many shallow lakes, Newburg stated.
“Aeration systems can certainly help,” Newburg explained, “but there are no guarantees that they’re always going to get every lake through the winter.”
Newburg pointed to Lake Elysian in Le Sueur County as an example.
Lake Elysian has suffered winterkills on a semi-regular basis over the years.
Two years ago, following a winterkill, the DNR stocked the lake, in good measure because Elysian has an operating aeration system.
“A good percentage of the walleye in Elysian this year would be in that 12 to 16-inch size, perfect for eating,” Newburg noted.
Unfortunately, Elysian was recently opened to liberalized fishing.
“Oxygen levels have dropped to such an extent that a fishkill is now very likely,” Newburg said. “Because Elysian is such a long lake, it really should have two aeration systems. We’ve only been able to arrange for one local organization to operate a system on the lake, however.”
DNR aeration policy is to find a club, city or organization that is willing to operate the system. DNR then provides the system but the sponsoring organization is responsible for the costs of maintaining and operating it and for ensuring the area is properly signed for safety.
Would a second aeration system on Lake Elysian have prevented a winterkill?
“It’s very possible but there is no way to guarantee that,” Newburg stated. “There are always variables involved that make it impossible to give guarantees.”
According to Newburg, it’s simple to identify the problems facing Minnesota’s shallow lakes. Conversely, it’s “tough as heck to implement solutions to the problems. There are just so many competing interests and wants out there.”
In Newburg’s vision of a perfect world for Minnesota’s shallow lakes, the following would occur:
Buffer strips would be in place along all tributaries in a lake’s watershed.
Lakeshore owners would plant vegetation along their shoreline (not remove it), and refrain from fertilizing their lawns.
Faulty septic systems would be repaired or replaced.
Local zoning ordinances would take a more proactive approach to protecting shorelands from over-development.
Citizens would embrace the fact that local decision-making is the key to making long-term lake improvements.
“We have a lot of lakes here in southern Minnesota that could truly become trophy fishing lakes ,” Newburg stated. “But not until we start treating them a whole lot better than we have been. Winter around here is what it is. Winter isn’t the problem. People are."
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