Few complaints as DNR draws down Swan Lake

By Joe Albert

Staff Writer

Nicollet, Minn. – The DNR’s decision to draw down Swan Lake met
with little resistance at a public meeting last week.

The drawdown began Dec. 6, two weeks after a DNR Fisheries crew
electroshocked a three-pound carp from the famed 10,000-acre
shallow lake. The water-level reduction is meant to kill any
remaining carp and will continue through the winter.

The DNR checked the lake after multiple duck hunters reported
they had seen carp there this fall. The discovery is the first time
carp have been documented in the lake.

‘The best and maybe only thing we could do was attack the
problem aggressively and quickly,’ said Joel Anderson, DNR area
wildlife manager in Nicollet.

That meant a drawdown.

As of last Wednesday, between three and four inches of water had
been drained from the lake. Officials aren’t sure exactly how much
water they’ll be able to drain during the winter, but hope to get
oxygen levels low enough (one part per million) to kill carp.

It’s unclear how many carp they’re dealing with. An hour of
electrofishing produced one carp, but five previous surveys dating
to 1967 never revealed carp, introduced in North America in the
late 1800s.

‘I don’t think it’s a huge population, but we don’t know,’
Anderson said.

Swan Lake is known to have other fish, including bullheads,
fathead minnows, sticklebacks, and green sunfish, but those haven’t
been detrimental, said Ken Varland, DNR regional wildlife manager
in New Ulm.

A few people at the meeting questioned how carp ended up in Swan
Lake.

‘There are just any number of ways carp could have gotten into
the lake,’ Varland said.

Among them, according to the DNR: through interconnected ditches
and streams; unknown inlets; up a lake outlet ditch from the
Minnesota River; and human activity.

A few of those at the meeting said they had seen minnow trappers
at the lake. ‘I’ve seen it with my own eyes,’ a cabin owner on the
lake said.

DNR officials say they have no evidence that minnow trapping
activities led to carp in the lake. ‘We have no evidence,’ said
Jack Lauer of the DNR Fisheries office in New Ulm. ‘We don’t want
to point fingers because we don’t know.’

The DNR may look into changing the rule so bait dealers can’t
use the watershed Swan Lake is located in, Anderson said.

The DNR also will explore whether carp may have gotten in from
the Minnesota River, about 11 miles from the lake. Swan Lake
empties into a ditch system that meanders through bean fields,
which in turn empties into Nicollet Creek. That creek empties into
the river.

There is a 10-foot waterfall in the Nicollet Creek stretch, and
it’s possible carp got over that during high-water years, officials
say.

What’s next?

Twice a day, DNR staffers are checking the outlet from Swan Lake
and the ditch system to ensure water is flowing properly.

As the winter goes on, they’ll test dissolved oxygen levels in
the lake and look for ‘refuge’ areas that may hold more oxygen than
the rest of the lake. Those areas, conceivably, are places carp
could survive even if most of the water in the lake doesn’t have
enough oxygen.

If those areas are found, and carp are there, two strategies
could be used to kill them: reverse aeration or a chemical
treatment.

While officials hope the drawdown eliminates carp, they say they
will check the lake when there’s no ice, and if carp remain, it’s
possible a chemical called rotenone could be used to kill the
fish.

But, ‘Rotenone would be kind of a last resort,’ Varland
said.

However, talk of rotenone dominated the discussion, as some
wondered what side effects it could have, what it would cost, and
how effective it would be.

Jon Schneider, manager of Minnesota conservation programs for
Ducks Unlimited was surprised by the number of questions about
rotenone. He related that on Lake Christina, a famed 4,000-acre
waterfowl lake near Ashby, a rotenone application cost about
$400,000 and didn’t eliminate all the fish.

Drawing Swan Lake down, he said, is the best option at this
point because the stop log structure at its outlet allows the DNR
to manually manage water levels. That option wasn’t available at
Christina.

‘We spent almost half a million dollars at Lake Christina
because we couldn’t do a drawdown,’ Schneider said.

DNR officials did say that, depending on how much water they get
out of Swan Lake, water levels could be low for next year’s
waterfowl season.

‘It’s a risk,’ Varland said. ‘But so is the carp. That’s a
bigger risk.’

Motorless update

A plan to close Swan Lake to motors to reduce disturbances to
waterfowl is under consideration in St. Paul.

The proposal was to close the lake to motors during the
non-hunting season. It would be open in August and during the
waterfowl season, Anderson said.

But a final decision hasn’t been made, and the DNR’s Waterfowl
Committee is expected to talk about the issue at a meeting next
month.

Categories: Hunting News

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