Invasive Asian carp less than 50 miles from Lake Michigan
Silver Asian carp leap from the Illinois River near Bath, Ill., on Sept. 8, 2010. Noise from boats causes the carp to leap.
DETROIT — The news is mixed as Great Lake states and the federal government continue to devote money and brainpower to stopping a potential Great Lakes ecological disaster — invasive Asian carp species making their way from the Mississippi River into Lake Michigan.
First the good news: The leading edge of the mass of bighead and silver carp hasn't made much progress lately up the Mississippi and connected rivers toward Lake Michigan.
"We really haven't seen the picture change for silvers and bigheads over the last few years," said Charles Wooley, deputy director of the U.S. Fish and Wildlife Service's Great Lakes Region. "That's really a good thing for those of us who are working on this."
Now the bad news: The younger fish — juveniles — are moving closer, the evidence shows. And they can do more damage.
Silver carp is a variety of Asian carp. Invasive Asian carp are getting closer to Lake Michigan.
Silver carp larvae were found in the Dresden Island Pool of the Des Plaines River, about 47 miles from Lake Michigan, in June 2015. Since young fish tend to drift with the currents, that means they were probably hatched about 10 miles even farther upriver, somewhere in the vicinity of the Brandon Road Lock and Dam near Joliet, Ill., O'Keefe said.
An Illinois program to harvest Asian carp near Peoria has helped keep adult numbers from spreading quickly, Herbst said. That program has removed nearly 4.5 billion pounds of Asian carp since 2011, most being exported for human consumption in China.
But that approach has its limits, O'Keefe said. The Chinese market is primarily for adult, bighead carp, he said. There's less of a market for the silver carp that make up the bulk of the biomass making its way up the river. And commercial fishing is more viable farther down the Mississippi River; but near the leading edge of the invaders in the Illinois and Des Plaines rivers, there aren't enough carp to make commercial fishing viable unless it's continually subsidized, he said.
Current markets also want adult fish, while managers seek to remove fish of all sizes.
"What's needed is a market for both fish, in varying sizes — pet food, fish oil," O'Keefe said. "No one's been able to develop a market for that at this point."
While there's no long-term data that can predict what will happen yet, "We're getting a little glimpse that we may have reached a stalemate in this movement, which is good," Wooley said.
Lake Michigan and the Mississippi river were originally connected in 1848, in a limited shipping canal system. To deal with a rapidly expanding Chicago's sewage overflows into Lake Michigan, a sanitary canal was built between the Chicago and Des Plaines rivers to move sewage to the Mississippi by 1900, which included engineering work to reverse the flow of the Chicago River from Lake Michigan in the opposite direction to the Des Plaines River.
The U.S. Army Corps of Engineers operates two electrical dispersal barriers near Romeo, Ill., about 37 miles south of Lake Michigan. A third electrical barrier upstream of the existing pair is also in the works, with an aim of making it more effective against juvenile fish, Wooley said. The Army Corps expects to have that completed sometime next year.
"There are no fish that are probing these electrical barriers on a daily basis," Wooley said. "The closest these fish are is about 15 to 20 miles downstream, and that leading edge hasn't really changed much in the past five or six years."
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