Invasive asian carp threaten to harm the food chain and disrupt the Mississippi River aquatic ecosystem.

While the media buzz about Asian carp may have slowed a bit over the summer, these invasive marauding fish certainly haven’t. And the Minnesota Department of Natural Resources has been busily preparing to implement barrier technology to slow their spread, some of which would likely be the largest of its kind in the world.

Fish farmers in the southern United States originally imported Asian carp to control snails and other small organisms in fish farms, but the invasive species escaped into the Mississippi River during floods. Their penchant for consuming copious amounts of plankton (the basis of the food chain) small organisms, paired with their large size — some can reach 100 pounds or more! — makes for a lethal combination that threatens to harm the food chain and disrupt the Mississippi River aquatic ecosystem.

While fewer than a dozen adult Asian carp have been found in Minnesota, it doesn’t take many to constitute a breeding population. For perspective, the U.S. Geological Survey reports that it would only take 10 adult males and 10 females to colonize the Great Lakes. Thus halting the spread is an urgent issue, with many of Minnesota’s treasured rivers, lakes and our $4 billion fishing and water recreation economy at risk.

Thanks to state Legacy funding and bonding appropriations, the DNR has been working to evaluate and construct barrier technology at several strategic locations to protect the Mississippi, Minnesota and St. Croix rivers, including:

• Mississippi River Lock #1 (Ford Dam),
• five sites in the Little Sioux River watershed in southwest Minnesota,
• a site in northwest Iowa,
• Lock #2 in Hastings,
• and the mouth of the St. Croix in Denmark Township/Prescott, Wisconsin.

The Lock #1 barrier would prevent Asian carp from getting further up the Mississippi River and keep them out of tributaries like the Rum River that leads to Lake Mille Lacs. The barrier at Lock 1 requires Corps of Engineers approval and includes evaluation of safety at the lock. As there has never been an electric barrier installed in a navigation lock this is a significant issue that will take time to resolve, and ultimately this decision belongs to the Corps.

The southwest Minnesota and northwest Iowa barriers would prevent Asian carp from getting into Minnesota from the Missouri River basin, or prevent them from crossing into subwatersheds if they do get into Minnesota. The five sites in southwest Minnesota could have barriers completed in one year, while the Iowa site could be done by the end of this year, which is the Iowa DNR's goal.

Identifying sites for barriers to protect the Minnesota and St. Croix rivers presents considerable challenges and could be extremely costly. Most of the Minnesota River Valley is so wide it would be inconceivable to erect an effective barrier, however the DNR is evaluating the possibility of installing barriers at a few constricted locations, including along or near Mankato’s flood control levee and Lock and Dam #2 on the Mississippi which is downstream from the confluence with the Minnesota. For the St. Croix, the DNR is exploring the feasibility of installing a barrier at its mouth, where it joins the Mississippi, near Prescott.

Aside from permanent dams, electric barriers are the most effective deterrent available. However, there are concerns about boater safety and potential risks to native fisheries. The highly qualified engineers who operate the Chicago Sanitary and Ship Canal’s electric barrier have encountered technical problems resulting in temporary shutdowns, power outages and other operational issues. At 165 feet across, the Chicago barrier is the largest known electric fish barrier in the world. Yet this barrier would be dwarfed by some of the potential barriers being considered in Minnesota. Lock and Dam #2 is 770 feet wide and both the Minnesota River at Mankato and the mouth of the St. Croix are over 500 feet wide. All three sites are deeper than the Chicago Ship Canal during floods, and experience greater flows. The Chicago barriers took many years to build and cost $35-40 million and over $1 million a year to operate and maintain. We can learn from the Chicago barrier, but with such width issues, Minnesota would be entering uncharted waters.

Electric barriers are a critical tool in the fight to stop the Asian carp invasion. However, it’s important to note that while they will considerably slow the spread of the fish, they may not completely stop them. Based on past experiences, many electric barriers have experienced unforeseen technical or weather-related problems and despite the best intentions are not 100% effective. (Asian carp lay millions of eggs, which hatch in fewer than 48 hours!)

With the understanding that it does not take very many adults to establish a population, Minnesota and the federal government must act quickly and strategically to ensure barriers are located where they can be most effective.

The advancement of electric barriers also underscores the need to close the Upper St. Anthony Falls Lock, which is by far the most cost-effective way to stop Asian carp from invading the Mississippi River north of the Twin Cities. This spring, a bill to give the U.S. Army Corps of Engineers authority to close the lock was introduced in Congress with bipartisan support, but political observers think it is unlikely to pass in the near term.

FMR supports moving ahead on both fronts — installing barriers as soon as possible and moving forward with a process to close the Upper St. Anthony Falls Lock should Asian carp arrive on our doorstep.

For more information about the Asian carp issue, please contact Irene Jones at 651-222-2193 x11. You can also stay informed through StopCarp.org, a website of the Asian Carp Coalition, a group of non-governmental organizations collaborating in their efforts to prevent the invasion of these harmful invasive species into Minnesota’s waters.

Tim Schlagenhaft of the Minnesota DNR contributed information for this story. He can be reached at timothy.schlagenhaft@state.mn.us or 651-345-3365 x233. Read more…