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Scientist: Asian Carp Not a Threat to Lake Michigan


A UWM School of Freshwater Sciences researcher shares his “big picture” view of the state and future of the Great Lakes, particularly Lake Michigan.

Last month the U.S. Army Corps of Engineers announced a $2.8 million contract to construct a new electric barrier in the Chicago Sanitary and Ship Canal.  It’s the latest in the Corps’ efforts to hold back the Asian carp from entering the Great Lakes.

Although recent samples collected from the Kalamazoo River in Michigan found no evidence of Asian carp, its DNA has previously been detected in Chicago-area waterways – as close as seven miles from Lake Michigan. But scientist John Janssen says Asian carp do not pose a threat to Lake Michigan. Number one, he says, Lake Michigan doesn’t have the food source Asian carp depend on.

"The Asian carp feed on the little suspended algae called phytoplankton," he says. "There’s virtually no phytoplankton in Lake Michigan left to sustain the Asian Carp."

Janssen, who has spent much of his career studying invasive species like the round goby, says "fertile" waters like the Mississippi and Illinois Rivers harbor plenty of the food stuff, but not Lake Michigan.

Not any more, at least - he says another invasive beat the Asian carp to it.

"In Lake Michigan the animal that's doing that job, and much more efficiently, is the quagga mussel, which is what replaced the much more familiar to the general public zebra mussel," he says. "Quagga mussels are so efficient they basically starved the zebra mussel out."

So while Asian carp might not have the food source to survive in Lake Michigan, Janssen says it is likely to be an issue in other parts of the Great Lakes, such as western Lake Erie.

"Because a lot of nutrients go in via the Maumee River which enters at Toledo...there's plenty of food in Lake Erie, and the Maumee River is very likely a very good place for them to spawn," he says. "That means that Asian carp are an issue at least for sections of the Great Lakes."

Janssen echoes what he says is a "big picture" consensus among scientists: the possibility of invasive species will not end with the Asian carp, unless the Great Lakes and Mississippi basins are severed .

"The issue is really the canal system around Chicago because that's a conduit for invasive species to go from the Great Lakes down to the Mississippi, which of course already happened with zebra mussels and quagga mussels and round gobies, etc.," he says. "And it's a conduit potentially for things that are a problem that become invasive initially in the Mississippi drainage to move into the Great Lakes. That is the big issue."

Janssen says making that separation happen is a complicated proposition requiring, among other forces,  sanitary engineering expertise along with a great deal of money.

Despite its challenges, the scientist describes Lake Michigan as being "pretty pristine," even as it's restablizing from previous invasive species.

"Anytime you see freshwater that's blue, you say that's really clean water," he says.

John Janssen in his School of Freshwater Sciences lab.

Ironically, Janssen says a major reason for its cleanliness resulted from the invasion of the quagga mussel. The scientist says you have to rewind to the arrival of the zebra mussels.

"The zebra mussel show up in numbers in the summer of 1991," Janssen says. "And the whole lake changes; it becomes a little blue. And now it's not unusual to have 60 feet of visibility because the quagga mussels have cleaned it up even more.  And that turbidity was the phytoplankton; the food that would go to certain fishes ultimately."

Janssen says generations of invasives have resulted in an altered  Great Lakes with a changed ecosystem.  Their fisheries continue to be challenged.

"I think it's time to rethink the ecosystem, all the way, and think of it as a ecosystem approach," he says.

Janssen is a researcher and professor with UWM’s School of Freshwater Sciences. His specialties are fisheries ecology and biological oceanography. Right now, Janssen and his students are immersed in the study of hatching round gobies – one Great Lakes invader - in Lake Michigan.

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Susan Bence entered broadcasting in an untraditional way. After years of avid public radio listening, Susan returned to school and earned a bachelor's degree in Journalism from the University of Wisconsin-Milwaukee. She interned for WUWM News and worked with the Lake Effect team, before being hired full-time as a WUWM News reporter / producer.