Saturday, February 4th, 2023
Saturday, February 4th, 2023

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DNR expects rebound after fish winterkill

Windom, Minn. – A recent scan of some southwestern Minnesota
lakeshore probably had local anglers fearing the worst – that the
harsh winter of 2009-10 had decimated fish populations.

But while winterkill, brought on by the depletion of oxygen in
the water, may have put a dent in some fish populations, the
resulting void could prove beneficial for the remaining fish,
according to the DNR.

“Most people around the local area … know that within one to
three years, they’re going to see a good fishery (in lakes that
suffered winterkill this year),” said Jack Lauer, DNR regional
fisheries manager in New Ulm.

DNR personnel in Windom are taking a look at losses in as many
lakes as possible, said Ryan Doorenbos, area fisheries supervisor
in that office. Thus far, dead fish have been documented in a
number of lakes, but several surviving fish have been netted, too,
in post-winter assessments.

There are some 18 lakes in the work area that experienced
winterkill to some extent, Doorenbos said. Whether or not each lake
is checked depends on if time is available to do so. “We’ll have to
play it by ear,” he said.

St. James Lake, located in the city by the same name, was one of
those recently netted, Doorenbos said, and the results were
somewhat unexpected.

“It turned out to be just fine,” he said. “That’s the one we
were sweating the hardest.

“There were good numbers of everything we’ve ever stocked in St.
James,” he said.

The nets contained a mix of bluegills, largemouth bass,
crappies, northern pike, walleyes, and many perch, along with a few
bullheads.

“It looks like it’s going to take care of itself,” Doorenbos
said.

St. James, like many shallow, bowl-shaped southwestern lakes,
utilizes an aeration system during the winter. However, conditions
this year rendered such systems mostly ineffective in some
cases.

“The aeration holes were not as big as in years past (due to
extreme winter weather conditions),” Doorenbos said.

The southwestern portion of the state received snow far above
average this winter. That snow cover limited light penetration,
thus reducing plants’ ability to produce oxygen. If vegetation dies
from lack of sunlight, the plants start to decompose, which uses
oxygen dissolved in the water, according to the DNR.

“(Winterkill) had everything to do with the snow cover,”
Doorenbos said. Early or heavy snowfall worsens winterkill; the
southwest had both.

Eventually, staff from Windom will evaluate a massive fish kill
that occurred in Murray County’s Lake Shetek. Lake residents and
others already have gathered up fish carcasses that filled some of
the lake’s bays and in some cases distributed them on farm
fields.

DNR Fisheries staff didn’t participate in the fish pick-up,
Doorenbos said. It’s not something the department does, in part
because of office vacancies, partly because of other spring duties,
and partly because of the extent of winterkill this year.

“We don’t go to every fish kill to pick up the dead fish,” he
said. “The reality is, it’s not just Lake Shetek where there were
dead fish. It’s a natural phenomenon that occurs in the area.”

Lauer said residents may remove fish carcasses without any
special permission, and he thanked those who removed the fish from
Shetek.

“Kudos to the people who stepped up and took ownership (of the
lake),” he said.

Most of the fish that perished in Shetek and neighboring Bloody
Lake were common carp, bigmouth buffalo, and channel catfish,
Doorenbos said.

While Shetek was slated to receive stocked walleye fry this
year, Bloody was not. But both will get fish, and Doorenbos expects
big things from the year-class, given the void created by the
winterkill. He said in the fertile southern lakes, stocked fish can
pull off excellent year-classes following die-offs.

For Eagle Lake, located between Windom and Mountain Lake, a fish
kill might open the door to a new stocking opportunity, Doorenbos
said. The small lake is managed for yellow perch, and a post-winter
assessment found the lake “absolutely loaded with perch,” he said,
adding that the lake needs a predator fish. He said it’s possible
northern pike could be stocked in the lake this year.

Timber Lake, near Jackson, also saw several carp and bigmouth
buffalo succumb to low oxygen levels. It’s another opportunity to
fill the void in biomass with predator fish, Doorenbos said.

The DNR’s netting assessment of Timber turned up nearly 700
black bullheads, and almost 2,000 yellow perch.

Doorenbos said his crew also will be netting Clear Lake in Lyon
County (near Russell), a lake in which there was a “pretty
significant” fish kill. Another area lake that “took a hit,” he
said, was North Fulda Lake in Murray County. There also are
concerns about Buffalo Lake, near Dovray in Murray County.

East Lake Stay, on the outskirts of Arco in Lincoln County,
“ranks right up there in terms of dead fish,” Doorenbos said. The
dead from that lake included walleyes, carp, and bigmouth buffalo.
The loss of fish could make way for a bumper crop of walleyes that
will be stocked there.

If there are a few fish left in lakes (brood stock), Doorenbos
said he’s confident they usually can effectively repopulate the
lake, given the reduced competition for forage and similarly
reduced chance of predation on the young-of-the-year. That’s the
reason he typically doesn’t open winterkill lakes to “liberalized”
fishing come late winter.

“We’re now going into systems post-winterkill and finding fish …
in numbers,” he said. “It’s the rationale we’re using for not
opening them to liberalized fishing.”

That’s not an absolute rule, Doorenbos added. “We look at lakes
on an individual basis.”

Another benefit: Fewer carp can mean improved water quality.

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