Day 5: Keeping Asian carp from Minnesota River will be difficult
By Tim Krohn Free Press Staff Writer
Add giant flying carp to the list of potential dangers to the Minnesota River.
Last month, officials found DNA from Asian carp in water samples taken from the mouth of the Minnesota River.
They have not confirmed the carp are in the Minnesota or upper Mississippi rivers.
Intense efforts are under way to keep the invasive Asian carp out of Minnesota waters. The fish, which can reach monster size and some which jump into the air when startled, are moving up the Mississippi.
State and federal officials, with a mandate by the Legislature, are devising plans to halt or at least slow their migration.
But some say the plans largely ignore keeping the carp out of the Minnesota River.
“ Their planning process has had no real consideration for the Minnesota River,” said Scott Sparlin, a river advocate from New Ulm who fishes the river often.
“I just get the impression they’re writing the Minnesota River off.”
But Jack Lauer, Department of Natural Resources regional fisheries manager in New Ulm, said there aren’t any feasible ways to block the carp from getting into the Minnesota River.
The existing plan, developed by state and federal officials and supported by Gov. Mark Dayton, is focusing on taking a stand against Asian carp near St. Anthony Falls in Minneapolis.
But the Minnesota River ties into the Mississippi several miles south of St. Anthony, leaving it wide open for any carp that make their way up the Mississippi.
Lauer said St. Anthony was chosen because it’s the one place the carp could possibly be held back.
“ The St. Anthony falls is a natural falls and a natural barrier (to fish),” Lauer said. But state officials face a hurdle because there is also a lock and dam there that lifts and lowers boats to navigate the Mississippi. That lock carries water from the lower falls to the river above — along with any fish in the water.
State officials are asking Congress to have the Army Corp of Engineers close that lock and dam if Asian carp are detected in the area, creating a permanent natural barrier.
“But that runs up against boaters and commercial interests,” Lauer said. If the lock can’t be closed, Plan B focuses on an area nearby on the Mississippi at the Coon Rapids dam. A barrier — possibly using a wall of constant bubbles that deter fish from swimming through — would be erected there.
As for the Minnesota River, some work has been done looking at possible places to use a barrier. But with no dams — except near the start of the river — it’s not very feasible, Lauer said.
“ There aren’t any natural barriers (like waterfalls) and no dams.”
Another issue is that there is barge traffic on the lower end of the Minnesota.
And he said, frequent and increasingly larger floods on the Minnesota would work against any barrier efforts as water often flows up over the banks, creating temporary lakes and wetlands that could give carp a way in.
Still, Lauer said it may be possible to erect some type of barrier on the Minnesota. “But should we spend so much money to try to stop one species?”
And, he said, any barrier would also keep native fish from coming into the Minnesota River. “ Sturgeon and sauger are species that need to travel long distances to find spawning.”
Fisheries workers are checking the Minnesota River for any sign of the four species of Asian carp, including the silver carp, which is the one that flies above the water.
“ We’ve been out electrofishing this summer and fall. There’s no presence of the carp.”
Fisheries workers also recently took 50 water samples from different spots on the Minnesota River to do “environmental DNA” testing, which can indicate whether Asian carp may already be present in the water.
This spring similar testing on the St. Croix River showed the presence of silver carp DNA.
Later netting turned up none of the carp. Officials said samples could have been unreliable because of high flood waters at the time.
Besides the Minnesota River, the new round of DNA testing includes more samples from the St. Croix and the Mississippi.
Early results from that round of testing found Asian carp DNA in the Mississippi River and in the mouth of the Minnesota River.
Sparlin said that if the Minnesota River isn’t protected, the river does have one thing working in its favor — there are a lot of native fish and fish species in the river.
There isn’t much research on the subject, but some think that areas with healthy native fish populations may make it harder for Asian carp to get established — or at least slow their spread — because the native fish will feed on small carp.
“ The Minnesota has a lot of fish,” Sparlin said. “ The lower 25 miles of the Minnesota isn’t too hot for fishing, but you get above that and there’s tons of fish,” Sparlin said.
Lauer agreed. “ With the existing game fish, with flathead and channel catfish, walleye, sauger, some predator species, it’s in pretty good shape to keep the Asian carp in check for a while,” he said.
“ The thing is we really have no idea what effect Asian carp would have on the Minnesota River.”