Keeping carp out of the St. Croix River calls for aggressive action

In honor of National Invasive Species Awareness Week:

Invasive bighead and silver carp could seriously disrupt the St. Croix River we know and love. They will eat all the food, drive out all the other fish, and leap from the water and into boats and boaters.

Bighead and silver carp eat plankton, which native mussels and fish depend on, consuming up to 20 percent of their body weight everyday, growing to 50-100 lbs.

Jumping carp have all but destroyed recreation on the Illinois River. And they have been found in the St. Croix River. But there is still time to stop the frightful fish; the closest reproducing populations are thought to be on the Mississippi River in Iowa.

A key emerging concept to stopping carp from invading new waters is to throw everything you can at them. Achieving “the maximum collective impact” is central to a plan recently released by a coalition working to keep carp out of the Great Lakes.

From bubble walls to electric currents, hot water to noise machines, numerous methods employed together can “dramatically reduce the Asian carp populations at locations near the electric barrier, resulting in a reduced threat of dispersal.”

A similar strategy is part of the recommendation from Minnesota carp researcher Dr. Peter Sorensen. In a St. Croix 360 article last year, Sorensen explained how his studies had shown that an $8 million upgrade to the lock and dam on a Mississippi River could keep carp out of the upper Mississippi, and the St. Croix, for a long time.

But the proposal got entangled in University of Minnesota bureaucracy, and the money was not allocated by the legislature in 2016.

The St. Croix River Association (a St. Croix 360 supporter) sees invasive species, including carp, as a priority. Executive director Deb Ryun wrote in SCRA’s spring newsletter that a healthy ecosystem might be the best defense against carp.

“Our cooler northern waters make their reproductive success less likely,” she wrote. “And predators such as muskellunge and northern pike are common in our waters, which may prove to be a semi-effective defense against the young should Asian carp reproduce in the St. Croix.”

But that’s not enough to comfort most people who love the St. Croix.

Last year, the St. Croix River Association undertook several efforts to address carp and the many other exotic plants and animals that could also have effects nearly as catastrophic:

• Completed an Aquatic Invasive Species Strategic Plan for the St. Croix River Basin
• Employed three summer interns who helped conduct invasive species education and outreach.
• Spent almost 350 hours at landings on the St. Croix River, encouraging nearly 700 boaters
  to clean, drain, and dry their boats and equipment.
• Distributed educational materials to more than 60 river- and lake-dependent businesses.
• Expanded K-12 aquatic invasive species education capabilities.
• Visited marinas along the Lower Riverway to provide invasive species information and partner on outreach to boaters.

What you can do:

The National Park Service recommends the following personal actions:

• Minimize use of Mississippi locks for watercraft travel (carp can swim upriver when the locks are opened). Consider trailering your watercraft around locks whenever possible.
• Don’t harvest bait or transport water from infested areas.
• Dispose of unwanted bait in the trash, NOT in water bodies.
• NEVER release fish from one water body into another.
• Report any new sightings
• Drain and rinse your boat when you are done boating
• Spread the word! The more people who know about the problems Asian carp cause and how they can help keep them out of the Great Lakes, the easier it will be to stop these fish.

If you catch or see an invasive carp, call 651-587-2781 or email invasivecarp.dnr@state.mn.us.

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