An area fisheries biologist based at the Windom office reported fish schooling below the dam, leading to the investigation and ultimate capture of 12 bighead carp, five silver carp and one grass carp on July 8 in a tributary of the Little Sioux River. The fish ranged in length from 17 to 35 inches.
DNR Invasive Fish Coordinator Nick Frohnauer said DNR fisheries personnel used a block net and large seine into the water body below the dam to capture and remove the invasive species.
While Frohnauer said he can’t say with 100% certainty that all of them were captured, he is confident all of the invasive species in the area below the dam were netted.
It is likely the three carp varieties reached the electric fish barrier through upstream movement in the Missouri River watershed. With prolonged high water conditions in the Little Sioux River last year and into 2020, normally shallow streams contained enough water for the fish to move upstream.
Invasive carp have been moving up the Missouri River watershed since escaping into the Mississippi River in Arkansas in the 1970s. These large fish compete with native species and pose a threat to rivers and lakes, according to the DNR. No breeding populations have been detected in Minnesota waters.
This is the second capture of invasive carp in southwest Minnesota.
In December, two silver carp were captured below the Lake Bella dam, south of Worthington. At Lake Bella, the dam structure makes it impossible for the fish to reach the lake. At Illinois Lake, the electric fish barrier was completed in the fall of 2015 for the specific purpose of blocking the invasive carp from the lake and moving farther upstream.
DNR fisheries staff conducts annual monitoring of Minnesota waters, and Frohnauer said the agency will be looking at its management plan now with this second discovery in the Little Sioux Watershed.
The electric fish barrier at Illinois Lake is one of eight projects the DNR completed in the Missouri River Watershed to protect aquatic resources by preventing expansion of invasive carp populations in southwest Minnesota.
The three species found at the Illinois Lake electric fish barrier are prohibited invasive species in Minnesota. According to the Minnesota DNR, all of the species were imported to the United States in the 1960s or 1970s to control aquatic plants in fish aquaculture operations and reservoirs. The species escaped during large flood events into the Mississippi and Missouri rivers, where they reproduced and established wild populations. They continue to spread through flood events and migration within connected river systems.
Bighead carp can weigh up to 110 pounds and grow to 54 inches in length. They are dark gray with black blotches on the back and sides. Bighead carp are native to southern and central China.
Silver carp can weigh up to 90 pounds and grow to 50 inches in length. They are silver in color and can be greenish on their back. If startled by the sounds of watercraft, silver carp can jump up to 10 feet out of the water. They are native to eastern Asia.
Grass carp is a very large fish in the minnow family that can weigh up to 70 pounds and grow to around four feet long. They are silver to olive in color and appear very similar to common carp, without the barbels or fleshy projections near the mouth. They are native to southeast Russia and northwest China.
For more information, visit dnr.state.mn.us/invasive-carp/index.html.
Invasive carp captures must be reported to the DNR immediately. Take a photo and transport the carp to the nearest DNR fisheries office, or make arrangements for it to be picked up by a DNR official by calling (651) 587-2781 or emailing firstname.lastname@example.org.