Four silver carp were captured this month in Pool 8 of the Mississippi River near La Crosse.
Rather than kill the destructive invaders, staff with the U.S. Fish and Wildlife Service fitted the fish with acoustic tags and released them back to the river.
On its face, it seems counter to every guidance on aquatic invasive species.
But the action was part of a multi-agency project to monitor the movements of the fish and learn their preferred habitats in the expansive pool.
Ultimately, it is hoped the "Judas" fish will reveal the location of other silver carp and guide netting efforts to remove the undesirable fish before they can strengthen their foothold in the Mississippi River along Wisconsin's western border.
The silver carp were caught by commercial fishermen contracted by the Minnesota Department of Natural Resources to look for the invasive fish. Other partners in the project are the Wisconsin Department of Natural Resources, U.S. Geological Survey and USFWS.
Once the four fish were captured, USFWS immediately dispatched a crew to insert acoustic tags in and release the fish.
“The more we can learn about these fish, the more effectively we can work to prevent their spread,” said Nick Frohnauer, invasive fish coordinator with the Minnesota DNR. “The ability to now track four silver carp gives us important data not only about how they act individually but also how they might move together and among schools of other fish.”
It's not the first time Asian carp have been tagged in the region - in 2017 a bighead carp was similarly fitted in the St. Croix River near Stillwater, Minn., and in 2019 a silver was tagged on the St. Croix near Hudson — but it was the first multiple-fish release.
Four species of Asian carp are found in the Upper Midwest — bighead, black, grass and silver. All are considered AIS and can cause severe damage to river and lake ecosystems in North America.
The bighead and silver have proven to reproduce in high numbers and be especially destructive. Since the fish escaped from Arkansas fish farms in the 1970s, they have been progressing up the Mississippi, Missouri, Illinois and Ohio river systems.
The large, plankton eating fish compete with native species and pose a severe threat to rivers and lakes.
The good news is no successful breeding has yet been documented by any species of Asian carp in Wisconsin waters of the Mississippi, Wisconsin or St. Croix rivers.
However, recent years have been yielding higher catches of the unwanted fish in Wisconsin and Minnesota border waters, topped off by 51 (40 silver and 11 grass) netted in March by commercial fishermen on the Mississippi near La Crosse and Trempealeau.
The fish, similar to the recent catch of four silver carp near La Crosse, were all adults.
Many conservationists fear it's only a matter of time before young-of-the-year Asian carp - an indication of local spawning - are found in Wisconsin or Minnesota waters.
"(Asian carp) are a huge concern for us, as they should be for everyone in the state and region," said Marc Schultz of Onalaska and a member of the La Crosse County Conservation Alliance. "This river is a precious natural resource and we need to do everything we can to protect it."
Fisheries experts hope the four silver carp will act as "traitor" fish and guide targeted netting and removal efforts of the invasive species.
The acoustic tags emit a signal that is detected either through a passive array of receivers placed in the river or by active means, typically with a receiver on a boat.
"Pool 8 has a lot of habitat, including backwaters, the fish may utilize," said Jordan Weeks, member of the Wisconsin DNR Mississippi River fish team based in La Crosse. "We'll be watching their movements to see if they use specific areas that could be key to removing them."
Research, including bubble and sound arrays, is being conducted on potential technologies to turn back the spread of Asian carp, but none has been shown as completely effective.
Tom Matych, an angler and conservationist from Twin Lake, Michigan, has long maintained the best method of combating the invasives is to keep native fish populations as strong as possible. Bass, walleyes, northern pike and even panfish such as yellow perch will gobble up young Asian carp, he said.
Matych advocates for added protections of native species as well as increased stocking efforts in certain waters and for certain species.
It is illegal in Wisconsin to possess, transport, transfer or introduce any species of live Asian carp.
If an angler catches an Asian carp, they should kill it and if possible put it on ice and take it to a local DNR office. If that is not possible, take a photograph of the dead fish and submit it to the agency along with details of where and when it was caught.
To report an Asian carp, call the DNR at (800) TIP-WDNR or the USFWS at (920) 866-1750.
The Link LonkOctober 25, 2020 at 04:54AM
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Four silver carp tagged and released on Mississippi River near La Crosse - Milwaukee Journal Sentinel
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