Out of sight is out of mind for many boaters along the St. Croix and Mississippi waterways. But that doesn’t mean the specter of invasive Asian carp isn’t lurking beneath the surface.
The carp—infamous for hurling out of the water in hordes (silver carp) and siphoning up vital plankton that native fish depend on (bighead carp)—have been making a northward trek up the Mississippi River since escaping into open waters from southern fish ponds in the '80s.
“I think we should be concerned that if they do become established they could affect a lot of our native fishes,” said Tim Schlagenhaft, a planner with the Minnesota Department of Natural Resources.
“It could affect our recreational use and they jump up out of the water so there’s some safety hazards," he said. “We should be concerned but I don’t think people need to panic. We do continue to monitor the developments.”
Schlagenhaft said he is hoping to change that and educate the public on the impacts these invasive aquatic species could bring.
“People should keep in tune to what’s going on,” said Schlagenhaft. “We are trying to address the problem long-term and address their populations should they become established.”
Critical Mass in the Mississippi and St. Croix rivers. A bighead carp was caught near Prescott, WI, in April sparking a resurgent effort to protect the natural and economic resources of the area.
If the troubling fish become established, as they have in many downstream locations, protective headgear may soon be fashionable during weekend cruises. One need only look at the Illinois River to see how fast the Asian carp population can spiral out of control and begin injuring boaters and waterskiers, as well as damaging that area’s native fish population.
Bighead carp can grow to 110 pounds and silver carp (the jumping kind) can bulk up to 60 pounds. Those can be big projectiles.
Schlagenhaft says Minnesota towns aren’t in danger of having those types of experiences yet, but added there is a lot they don’t know.
“Downriver, they started showing up in small numbers and then all of a sudden they reach a critical mass,” said Schlagenhaft. “Either the timing is right or the river conditions are right or they have a certain critical mass of the population that spawn, and the population grew quickly.
"But it’s a different river down there," he said. "We’re not certain what the populations will do up here.”
A multi-agency effort is underway through the National Park Service, Minnesota and Wisconsin DNR, and a hodge-podge of local governments and non-profit organizations to protect the Mississippi and St. Croix waters from Asian carp.
“It’s been evolving,” Schlagenhaft said of the efforts. “It’s was an ad hoc informal task force formed last January that evolved. That group developed an action plan, that was the main focus of that group. Now that we have that, we’re trying to implement that.”
That action plan includes the recently completed DNA testing as well as studies to plan for prevention as well as control should populations become established.
“We’re looking to cover all areas,” said Schlagenhaft.
have been proposed as possible barriers to stop the northward march. But those solutions would leave the St. Croix and anywhere downriver of an effective Mississippi barrier vulnerable to the spread.
Technological barriers that employ bubbles, sound and light are being discussed for deployment at the mouth of the St. Croix River and some Mississippi locks further downstream, but many experts agree those would be far from 100 percent effective.
So far, about a dozen Asian carp have been found along the Minnesota and Wisconsin riverways since 1996. So they are here. The questions remains as to in what numbers.
Schlagenhaft is concerned about the number of positives in the recent DNA testing results but said interpreting those results is difficult.
“We’re not exactly sure what that means,” he said of the results. “The positives mean there’s Asian carp DNA in the water, but not necessarily from live fish. It could be other sources. We’re assuming there’s live fish because the risk is significant. But we’re continuing to learn and try to sort out what the DNA is telling us at this time.”
Schlagenhaft says he considers the St. Croix and Upper Mississippi are seeing “the leading edge” of what could be an unwanted wave, but admits there is no evidence as of yet to suggest the fish are reproducing or that population levels are increasing.
A recent check with Hudson and Stillwater marinas revealed only passing chatter of Asian carp. “Nobody has really seen any in this area,” said Barb Lockway of Wolf Marine in Stillwater. “I don’t really know much about them, honestly. No one’s really talking about it.” Other area marinas contacted along the St. Croix echoed those statements.
Still, he urges boaters and fishermen to take precautions to prevent the spread and report any sightings to the DNR.
“Don’t transport bait from one water body to another,” he urged. “These small Asian carp look similar to other bait fish. If they catch a fish, they should keep the fish and contact the DNR as soon as possible. We would come out to investigate that fish.”
For more information of Asian carp, visit www.asiancarp.us, the Minnesota DNR website, or the Wisconsin DNR website.