Researcher talks ducks and minnows

As a result, some have linked fatheads to the duck decline.

“Our data don’t substantiate that claim,” Hanson said. “On a
site level, we can show and we have shown that if you decrease the
availability of aquatic invertebrates, you make foraging difficult
for young ducks.”

But applying that research to a landscape level and saying
fatheads are causing a decline in the duck population shouldn’t be
done, Hanson said, because a female duck likely would take
ducklings to a place with more food, rather than stay at a place
with little food.

The walleye study

The question, then, becomes how to control fatheads.

Whereas previous studies looked at the relationship between
fatheads and water quality, another study Hanson was part of aimed
to evaluate how walleyes influence fathead minnow populations.

The three-year study included six wetlands stocked with walleye
fry, six wetlands stocked with year-old walleyes, and six wetlands
without any walleye stocking.

“There were rather dramatic influences on those resident
populations of fathead minnows in the fry stocking wetlands,”
Hanson said. “Specifically, what was perhaps the most dramatic was
the influence the walleye fry had on recruitment of fathead
minnows. Those fry stockings were successful in dramatically
limiting the recruitment of fathead minnows.”

Additionally, fry stocking resulted in greater abundance of duck
foods, like amphipods. However, researchers said fish should be
removed each fall from the wetland to prevent the walleyes from
feeding on aquatic invertebrates.

The ponds stocked with walleyes one year and older didn’t have
similar results. In those, the consumption rates of fatheads wasn’t
high enough to reduce the minnows’ abundance.

Interconnected wetlands

Hanson, Sternberg, and Roger Pederson of Ducks Unlimited are all
of the opinion that the connection of wetlands is one of the
biggest problems facing wetlands today.

“That’s really the big problem, more interconnectedness,”
Sternberg said. “All the draining and tiling and the water levels
keep going up, everything keeps running together, and the fish are
just kind of moving across the countryside.”

Said Hanson: “We have ditched the daylight out of the prairie
landscape. As we move water around, as we connect for the purpose
of consolidating and eliminating water, as we connect complexes of
wetlands, we are providing travel corridors for migration of these
fish.”

There’s no data that shows the range of fathead minnows has
changed, but they are now found in more wetlands because of wetland
connection.

“They are having what we think are disproportionate ecological
influences because of human-related alteration of the landscape,”
Hanson said.

Anyone concerned about wetland quality aquaculture for
harvesting and raising fish, duck hunters for waterfowl habitat
should be concerned about interconnectedness because of the spread
of fish like black bullheads and fatheads, Hanson said.

“It’s a problem for the fish growers, and it’s also more than
likely a problem for the avid waterfowl enthusiasts,” Hanson said.
“That’s not consistent with high-quality wetland habitat.”

Ducks Unlimited isn’t against the aquaculture industry, but
wants to see wetlands used in a sustainable manner, and have some
that are managed only for ducks, Pederson said.

“There’s just a lot of pushing the state toward a fish-dominated
system,” Pederson said. “We’re not trying to take the fish out of
everything, but there are things management can do to make them
better.”

The agreement

The aquaculture industry and duck hunters have a lot of concerns
in common. They disagree on specific details, but are generally in
agreement about the more important landscape issues, Hanson
said.

“We differ somewhat in the special interest that we bring to
this,” Hanson said. “The fish people have some interests that
aren’t shared by our avid waterfowlers, and vice versa. But there
is a broad area” of agreement.

Things such as agricultural practices that contribute to poor
water quality are concerns for both sides.

“Most of the things that really impinge on wetland quality would
threaten both of the groups populating both of these poles,” Hanson
said.

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