New evidence of Asian carp in Wisconsin waters
Published: August 11, 2011 by the Central Office
Contact(s): Bob Wakeman (262) 574-2149; John Lyons (608) 221-6328; Ron Benjamin (608) 785-9012; Steve Hewett (608) 267-7501
MADISON - An angler's catch of a bighead carp in the Lower Wisconsin River and traces of silver carp DNA -- the carp known for its jumping behavior -- in the St. Croix River late last month have state officials calling on the federal government to direct funding and attention to aquatic invasive species in the Mississippi River system.
The two Asian carp species, which have been steadily moving upstream, are among a growing list of invasive species threatening Wisconsin waters of the Upper Mississippi River.
"High water levels on the Mississippi River are enabling more Asian carp to move farther into Wisconsin waters," says Bob Wakeman, who coordinates Department of Natural Resources efforts to prevent and control the spread of aquatic invasive species.
"Their presence is not a big surprise because their numbers have grown tremendously in the lower Mississippi and Illinois river systems and stray fish have reached Wisconsin before. But it's a big concern because of the potential damage they can do.
"We need the federal government to recognize the importance of the Mississippi River basin's invasive species problem and give it the attention and funding it deserves."
Wakeman says DNR also needs anglers and boaters for their help in keeping these fish from getting established in the Upper Mississippi, and in the Lower Wisconsin and St. Croix rivers, two of the most pristine rivers in the country.
Anglers and boaters can help by continuing to follow state rules to prevent the spread of invasive species continuing to follow rules to prevent the spread of aquatic invasive species and the fish disease VHS, and by reporting when they catch a bighead or silver carp or the closely related grass carp and black carp, Wakeman says.
"Please take a photo of it, note where you caught it, put it on ice and bring it to a local DNR office," he says. "We need everybody's help to keep our fishing strong and our rivers healthy."
Bighead and silver carp eat plankton and can potentially decrease populations of native fish that rely on plankton for food, including all larval fishes, some adult fishes, and native mussels. Bighead carp can eat 20 percent of their own body weight in food each day, and can grow to 60 inches and 110 pounds. Silver carp also have been known to jump out of the water and injure boaters.
DNR is supporting Minnesota's efforts to use electrofishing boats and nets to look for fish below the St. Croix Falls dam, where the silver carp DNA was detected earlier this month. Bighead or silver carp have been captured in the Mississippi River along Wisconsin's western border since 1996 and a bighead carp was captured at the mouth of the St. Croix River earlier this year.
The DNR also is partnering with the University of Notre Dame and others to collect water samples to test for Asian carp DNA from the Milwaukee, Kinnickinnic, Menomonee, Sheboygan, and Root rivers, and the Milwaukee, Sheboygan, Racine and Kenosha harbors. The Milwaukee, Kinnickinnic and Menomonee rivers were sampled last year and no DNA from Asian carp was detected. The Great Lakes and Mississippi River basins are artificially connected by the Chicago waterway system.
No signs of Asian carp reproducing in Wisconsin waters
The silver lining to the recent findings is that no young Asian carp nor other signs of successful reproduction have been documented so far in any Wisconsin waters, says John Lyons, a longtime DNR fisheries researcher and fish identification expert.
Also, dams on the Wisconsin River at Prairie du Sac and on the St. Croix National Scenic Riverway at St. Croix Falls will block the fish from travelling farther inland, and measures already in place can help slow the spread. [A fish passage planned for the Prairie du Sac dam has been designed to prevent invasive aquatic species and fish from getting further upstream.]
"The population densities are real low -- the bighead and silver carp entering the Upper Mississippi are mainly strays so there really isn't a critical mass up here yet," Lyons says. "Will there ever be? And what is the critical mass? It's a big unknown."
Wisconsin has taken actions within its own borders to slow the spread of Asian carp and other invasive species, ranging from banning the sale, transport, possession and introduction of bighead, black, grass and silver carp, to enacting ballast water treatment standards, to banning harvest of bait fish from the Mississippi River and its tributaries. That's important because young Asian carp resemble gizzard shad and many minnows, and DNR doesn't want Asian carp to mistakenly be harvested and taken to another water for use as bait, according to Ron Benjamin, longtime DNR fisheries supervisor on the Upper Mississippi River.
Wisconsin also is supporting research to find ways of eradicating aquatic invasive species or at least limiting their ability to spread to other waters, and DNR has worked with other states and federal agencies along the river to develop action plans to slow the spread of carp and other invasive species.
Federal attention and funding, however, has shifted to the Great Lakes region in recent years as concerns grew that Asian carp from the Mississippi River system might invade the Great Lakes, Benjamin says.
While the Asian carp can be blocked from reaching the Great Lakes by severing the connection between the two basins, options on the Mississippi River are more limited, the DNR officials say. The dams on the Upper Mississippi River itself are not high enough to be complete barriers to the Asian carp moving upstream, and the chance of closing down the locks, a decision that would need to be authorized by the U.S. Congress, is very small, Lyons says.
Benjamin hopes the recent findings will help bring federal attention back to the Mississippi River, noting that Asian carp were brought to the United States by the aquaculture industry in cooperation with federal agencies. "I hope that the recent finding will refocus some attention and funding the Mississippi to help implement a multi-state plan to prevent the introduction of new aquatic invasive species within the basin, and to prevent those already here from expanding into unconnected ecosystems," he says. "Finally, one of our best defenses is to keep our ecosystems healthy and diverse."