Environmental testing has found that a species of the invasive Asian carp likely is present in the St. Croix River, as far north as St. Croix Falls, Wis.
No positive samples of carp DNA were found in the Mississippi River, but researchers say that's not proof positive that the carp are not there.
Asian carp are considered a threat to native species and entire eco-systems. State and federal officials vow to conduct an all-out campaign to hunt down Asian carp in Minnesota waterways, and to try to stop its spread.
Researchers collected 50 water samples on both the St. Croix and the Mississippi Rivers. On the St. Croix, researchers focused on a four-mile stretch from the St. Croix Falls Dam downstream to the town of Franconia. That's about 50 miles upstream from Prescott Wis., where the St. Croix joins the Mississippi. Tests on 22 of 50 samples came back positive for silver carp.
The silver carp is the most notorious of the four species of Asian carp. It jumps wildly out of the water at the sound of a boat motor.
On the Mississippi, researchers took samples from the Ford Dam in St. Paul, downstream to just above the confluence with the Minnesota River. Those samples all came back negative for Asian carp. But scientists say because the river was at flood stage, the tests are not conclusive.
Two non-profit groups contributed about $20,000 to hire a consulting firm to do the testing at the end of June.
Tom Landwehr, commissioner of the State Department of Natural Resources, said the news about the St. Croix is disappointing. Later this month, the department will hire commercial fishermen to trawl the St. Croix and Lake Pepin in the Mississippi, using nets to try to catch any live carp that may be there. That will give a better idea of how many carp are present.
DNR officials also plan to conduct more environmental DNA tests on state waterways, including in the Minnesota River.
Landwehr said the next step likely will be to erect? a barrier against the invasive fish somewhere in the St. Croix.
"We are going to proceed with development of a sonic and bubble barrier on the St. Croix, pending the outcome of those additional surveys," Landwehr said. "We want to make sure if we implement a barrier it'll be effective, that the cow isn't already out of the barn."
Most likely the sonic and bubble barrier would be installed near Prescott at the mouth of the St. Croix. It's expected to cost $7 million for materials alone. A barrier of this type has been used in California to deflect fish from one river into another one.
Landwehr defended his agency for not acting sooner. He said no one is sure whether the barrier will work, and other agencies like the U.S. Army Corps of Engineers and the state of Wisconsin need to be convinced it's a good idea.
As for the Mississippi, citizen groups are pushing to at least consider closing some of the locks at dams operated by the Corps of Engineers.
But Russel Snyder, project manager for the St. Paul District of the Corps of Engineers, said it has no authority to close a lock to fight invasive species. Congress has only empowered the corps to address navigational issues.
"We do have a 2007 Congressional authorization for studying and implementation of a barrier similar to what was discussed here, acoustic or electric," Snyder said. "However, Congress has not appropriated any money for that, so that is a potential avenue for assessing and possibly implementing a barrier system."
Such a barrier would be located in a lock chamber or between locks, and it would not close the lock completely.
A handful of Asian carp have been caught in both the Mississippi and St. Croix rivers in the last four years.
As for how to pay for the new war on carp, the chairman of the Legislature's House Environment Committee, Rep. Denny McNamara, R-Hastings, said money from the Legacy Amendment could be available next year.
McNamara said the DNR has $5.6 million for aquatic invasive species that it could use to combat Asian carp. The department could make commitments for the first stage of the barrier through the state fisheries budget, he said.
"There's some options available that will allow us to react quickly to the needs," McNamara said. "If we build a barrier between Minnesota and Wisconsin, my hope is Wisconsin will be paying half the bill."
Meanwhile, the Wisconsin Department of Natural Resources announced Thursday it has found bighead carp in the Wisconsin River.