Study finds pollution in area waterways may be keeping Asian carp from advancing to Lake Michigan
CHICAGO (CBS) -- Lake Michigan may be benefiting from a bit of irony.
A new study from the University of Illinois suggests that pollution in Chicago's waterways is protecting the lake from invasive Asian carp.
In the study, "Silver carp experience metabolic and behavioral changes when exposed to water from the Chicago Area Waterway," researchers Amy E. Schneider, A.J. Esbaugh, Aaron R. Cupp, and C.D. Suski found that over the past decade, Asian carp have not spread beyond a certain stretch of the Illinois River.
The study found that the fish appear to change their behavior the closer they get to Chicago.
"Several possible hypotheses can explain this lack of upstream movement, including a scarcity of suitable habitat, low availability of food resources, or low population densities at the leading edge due to harvest efforts farther downstream," the study said. "An additional, alternate hypothesis to explain why the invasion front of silver carp has not expanded farther upstream is that they are being deterred by the presence of anthropogenic bioactive contaminants coming from the Chicago Area Waterway System (CAWS), and these contaminants are reducing habitat quality."
The study noted that the alternate hypothesis had not been tested directly, and the researchers conducting the study set out to do just that. They placed young carp in a container filled with polluted water from the Chicago Area Waterway System—and almost immediately, the fish started swimming slower.
The study concluded that there is some contaminant in the water of which the carp are not fond—and this indeed is likely why they have not advanced along the Illinois River in 10 years.
"Results from the current study showed that silver carp display decreased swimming activity and increased energy consumption when exposed to CAWS water, which was not apparent for animals held in control water, providing a putative, energetic mechanism for the lack of range expansion of silver carp within the CAWS," the study said.
The invasive Asian carp is considered a big threat to native Great Lakes fish. They were the subject of a heated controversy about a dozen years ago—in which other Great Lakes states unsuccessfully sued to have the locks on the Sanitary and Ship Canal closed so as to keep Asian carp from making their way to the Mississippi River to Lake Michigan and the other Great Lakes.
In 2022, the Illinois Department of Natural Resources campaigned to have the Asian carp, or silver carp, rebranded as "copi"—in hopes of getting people more interested in eating the fish.