The netting of an invasive silver "flying" carp on the St. Croix River is being seen by Minnesota conservation officials as a "disappointing but not surprising" discovery.
The notorious breed of carp, known for flying out of the water to the peril of boaters, was snagged by a commercial angler on the river in early April during seasonal netting between Hastings and Prescott, Wis., the Minnesota Department of Natural Resources (DNR) said late Monday.
It's the same location, at the mouth of the river, where the first silver carp in the St. Croix was captured in 2017.
"Captures of individual invasive carp are disappointing but not surprising," said Nick Frohnauer, DNR invasive fish coordinator. "This silver carp was captured in an area that is heavily fished in the spring, as it is an overwintering area for several species of fish."
The DNR has known for several years that carp can circumvent the lone barrier it has been operating in the lower Mississippi River, at Lock and Dam No. 8 near the Iowa border. A team of University of Minnesota researchers and the DNR have been testing electronic barriers and speakers at the dam, which can theoretically blast enough noise to deter carp from attempting to breach the spillway. But some of the biggest carp have proved that they can still swim through in the early spring, when spillway gates are lifted high and water velocity drops.
The U is still working on the technology and plans to install an upgraded system this year.
Prof. Peter Sorensen, who led the design of the system, has long said that about 50 miles upstream from the Iowa border — a bit north of Winona — there is another lock and dam system that shoots water out at a higher velocity and would make carp breaches even more rare if similar sound barriers were installed. But none has been added.
Once carp make it past the Winona lock and dam, there is nothing to prevent them from getting into the St. Croix or, worse, the Minnesota River. Given the polluted and deteriorated conditions of the Minnesota, biologists believe the tough bottom-feeding carp would quickly thrive and spread.
Breeding populations of any type of invasive carp have yet to be detected in any Minnesota waters.
Various breeds of invasive carp, native to China, were brought to the United States to cleanse algae from fish farms and sewage treatment ponds in the South. They have been moving upstream since escaping into the Mississippi River amid flooding in the 1970s.
The commercial angler who made the latest discovery immediately contacted the DNR about the fish, a 26¼-inch male weighing 7 pounds. DNR staff are working with the angler to conduct additional netting at the location of the capture.
The fish are considered damaging because they out-eat native species and create a nuisance for recreational boating. Online videos show silver carp flying out of the water and landing in boats and striking their occupants. One video, which has been viewed roughly 6 million times, shows two boaters ambushed by silver carp along the Wabash River in Indiana.
Single invasive carp have been caught as far upstream in the Mississippi River as near the Twin Cities (bighead, grass, and silver); the King power plant on the St. Croix River by Oak Park Heights (bighead); and just downstream of Granite Falls in the Minnesota River (bighead).
The DNR requires anglers to report invasive carp immediately by calling 651-587-2781 or e-mailing invasivecarp.dnr@state.mn.us. More information about invasive carp is available at mndnr.gov/invasive-carp.
Staff writer Greg Stanley contributed to this report.
