Asian carp

Minnesota, Wisconsin Conduct Carp Harvest In Upper Miss Pool 8

Beginning April 5, the Minnesota Department of Natural Resources conducted a joint intensive carp-harvesting operation with the Wisconsin Department of Natural Resources to remove invasive Asian carp from Pool 8 of the Mississippi River. Pool 8 extends from Lock and Dam 8, located near Genoa, Wis., upstream to Lock and Dam 7, located near Dresbach, Minn.

The effort used the innovative Modified Unified Method (MUM) that combines netting and herding techniques to drive and concentrate invasive carp from a large area of water into a small zone for removal. The two agencies say this is the first time the MUM method has been used in Minnesota or Wisconsin waters, and the first time it has been used anywhere as an early detection and rapid response technique. Other partners include the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service.

The MUM exercise was designed as part of a response to the capture of 39 silver carp and 12 grass carp in Pool 8 in March 2020. To date in 2021, eight additional invasive carp have been captured in or near Pool 8. The goal is to remove invasive carp present in Pool 8, curb the potential for invasive carp reproduction and prevent their establishment in the Upper Mississippi River Basin. The operation will yield more detailed information about any current invasive carp presence in Pool 8.

This thorough search and removal effort took place over a period of seven to 10 days. Progressive areas of Pool 8 were closed for one to three days during this time, temporarily suspending commercial fishing and recreational use. The operation paused Saturdays and Sundays, due to typically higher weekend boat traffic. The DNR has been contacting commercial fishing operations and others who might be affected to inform them of the effort and share the expected long-term benefits.

The MUM method, developed by the USGS, uses block nets to create compartments or “cells” from which the fish can be driven. The USGS then uses electrofishing boats and boats outfitted with underwater speakers to herd carp from each cell. When a cell is cleared, another net is used to close the cell and prevent the fish from returning. This process is repeated one cell at a time, gradually reducing the area available to the carp and concentrating the fish into a harvest removal area, where a large commercial seine is used to draw out the congregated fish. Native fish do not seem to respond in the same way as the invasive carp, preferring to hide, rather than run, from the sound stimulus.

Five invasive carp previously tagged with acoustic transmitters will complement this effort by increasing effectiveness of targeting fish in Pool 8 and providing insights into their movements and other behaviors.

“Thanks to the Minnesota Department of Natural Resources, we continue to break ground in the effort against invasive carp in our waters,” said Christine Goepfert, associate director of the National Parks Conservation Association and co-lead of the Stop Carp Coalition. “This field exercise to reduce carp in the Mississippi River is a positive step forward. This effort will help protect waters upstream, including the national park waters of the Mississippi National River and Recreation Area and the St. Croix National Scenic Riverway.”