DNR proposes plan to stop spread of Asian carp
WORTHINGTON — When the Minnesota Department of Natural Resources closed a gate on Herlein-Boote Slough north of Worthington in January 2012, to stop water from flowing through a diversion channel and into Okabena Creek, it was a temporary fix to try and stop invasive fish species like big head and silver carp from making their way into the Des Moines River Watershed. Now, the DNR plans to implement permanent solutions to fight the spread of invasive rough fish.
During an open house in Worthington Wednesday afternoon, officials with the DNR Fisheries office in Windom and representatives from Bolton & Menk Engineering and Surveying discussed plans with interested landowners regarding the proposed $140,000 project.
Duane Hansel, project engineer with the Sleepy Eye-based engineering firm, said plans include removing the gate system on the east side of Herlein-Boote Slough and permanently cutting off water flow into the Okabena-Ocheda Watershed District and greater Des Moines River Watershed. In addition, a dike is planned on the north side of the slough, where there is also potential for outflow from the slough during high water levels. The DNR is working with landowners to gain access to construct the dike.
As the DNR works to remove the east gate and close off outflow both east and north, plans also include increasing the pipe outlet for westward flow to the Rock River. At this point, a 24-inch outlet is in place, and it will be expanded to 54 inches to handle the water flowing out.
“The hope is that if we can secure permits, we could do the work yet this winter,” Hansel said. Three permits are needed to do the work — two from the DNR and one from the U.S. Army Corps of Engineers.
“I think it’s a high priority, high profile project for the Department of Natural Resources,” he added. “That’s the reason it’s fast-tracked, to get it done.”
Up until the east gate was closed in January 2012, the water in Herlein-Boote Slough flowed in two different directions — west into the Rock River, part of the Little Sioux Watershed, and east into Okabena Creek, part of the Okabena-Ocheda Watershed District and the greater Des Moines River Watershed. The water flow was split in the early 1980s, when a diversion channel was constructed to bring water from Herlein-Boote toward Worthington during periods of low water.
The diversion never worked as intended, however.
When Lake Okabena was low, so too was Herlein-Boote Slough; and in large rain events and high water levels, Worthington didn’t need or want the extra water flowing out of Herlein-Boote.
Now, it isn’t excess water that’s fueling the push to block off the diversion. Asian carp have been on the move and are knocking on Minnesota’s door. DNR Windom Fisheries Supervisor Ryan Doorenbos said while there has not been confirmation of species like big head or silver carp in the Rock River, they are “pretty prominent” in the Big Sioux River, which the Rock River flows into.
“Where flow is running in, they will find it,” Doorenbos said Wednesday, adding that if both gates to Herlein-Boote Slough had remained open, it would have become a highway for the Asian carp to infest waters in Minnesota and much of Iowa through the Des Moines Watershed.
Already, Herlein-Boote Slough is believed to have been the mode of travel for certain fish that have typically not been found in local waters.
Doorenbos said during a fish survey on Lake Okabena in 2004, netting efforts captured two short-nosed gar — a fish species never caught in the lake in the history of netting. Then, in 2010, a freshwater drum (commonly referred to as a sheepshead) was netted in Lake Okabena. Both species are prevalent in the Sioux and Rock River watersheds.
The ability for Asian carp to get into Minnesota waters is much more disconcerting. They are more prolific, grow faster and bigger than common carp and can consume up to one-third of their weight per day in zooplankton, the food necessary for fish like walleye and northern pike to survive.
“They are very good swimmers — three times better than common carp,” Doorenbos said.
Stopping the Asian carp at Herlein-Boote Slough is just one of the steps the Minnesota DNR is taking to keep the invasive species out. Doorenbos said there are half a dozen projects taking place in Jackson County, from removing some township culverts to reinforcing dike systems and planning additional electronic fish barriers.