Two invasive carp netted late last week in Cottage Grove, their northernmost point along the Mississippi River so far, stirred merely moderate concern for now.
Commercial fisherman under contract with the state Department of Natural Resources captured a 40-pound bighead carp and a 20-pound silver carp in Pool 2 of the river, the DNR said. Regional fisheries manager Brad Parsons said the discovery is “disappointing but not entirely unexpected.”
The agency will set additional gill nets and traps this week to determine whether more or younger, smaller invasive carp are in the Grey Cloud Slough area, a backwater lake for Pool 2.
The capture of the two is the first evidence that bighead carp have advanced past the mouth of the St. Croix River near Prescott, Wis. Silver carp had previously not been detected above Pool 5A near Winona.
Peter Sorensen, a leading anti-carp fighter and University of Minnesota professor, referred to the captured carp as “two rogue individuals who are not going to do much damage.” Sorensen said it would have been “incredibly concerning” if the carp had been young because that would be an indication of active reproduction. He warned that, “it’s certainly a sign that if nothing’s done, they will continue to move north. It’s another wake-up call.”
Within the next two weeks, Sorensen is heading down to Iowa to Lock and Dam 8 to install acoustic deterrents in the water in an attempt to keep the carp south. He’s also working at the university’s Aquatic Invasive Species Center to develop a velocity field that would be too strong for the carp to breach.
Ann Pierce, section manager at the DNR’s ecological and water sources division, said the find doesn’t appear to show that the carp population is established in Pool 2, but she said additional research will yield more information.
The DNR doesn’t know how long the carp were in Pool 2, but invasive carp migrate in high water and the Mississippi was very high for a long time this spring and summer.
Parsons said the discovery does not necessarily mean a breeding population exists within Pool 2. But he said both fish were females that contained eggs.
Sorensen said fish generally are not good breeders so it takes them awhile to establish themselves.
Silver and bighead carp can grow to 60 pounds and consume large amounts of plankton that native fish rely on. The silver carp are the ones often seen jumping from the water.
The carp, native to Asia, were introduced in the southern United States about 30 years ago. They now threaten ecosystems of lakes and rivers throughout the South and Midwest.