U.S. Water News Online
CHICAGO -- At one time the Chicago River was so polluted
that no fish could live there, and now scientists are considering a
longshot idea to make it unlivable again to prevent exotic species
from using the river to migrate between the Mississippi River and
Killing the river would buck the Clean Water Act and set an ugly
example of environmental policy. But biologists foresee ecological
and economic disaster from invasions of giant carp, zebra mussels and
``We've done marvelous things with the Clean Water Act, and nobody
wants to undo that,'' said Jerry Rasmussen, a river biologist for the
Fish and Wildlife Service.
The Chicago River flows backward, away from Lake Michigan, because
19th century Chicagoans engineered it to carry pollution away from
their beaches and into a canal. The canal flows to the Illinois
River, a tributary of the Mississippi, creating a link unintended by
Until aerators were used in the 1970s to pump oxygen into the
water, Chicago's waste polluted the river and canal. The Metropolitan
Water Reclamation District has since brought the manmade waterway
into federal compliance.
But now that the waterway can support native fish, nonnative
invaders can live there too.
Zebra mussels, drifting from Lake Michigan to the Mississippi 300
miles away, have cost an estimated $5 billion in clogged water
intakes and damage to fisheries, according to the Environmental
Asian bighead carp are swimming in the other direction. The
100-pound, plankton-straining species were imported to clean
Mississippi Valley fish farm ponds. They escaped during floods and
are within 25 miles of Lake Michigan.
Rasmussen and others fear bigheads could destroy the lakes' food
As a coordinator at the agency's Rock Island office, Rasmussen
suggested river-killing among several options in an analysis for
States routinely use smaller kills to eliminate nonnative or
``trash'' fish. In September, Maryland poisoned a 4-acre pond to kill
more than 1,000 rapacious Asian snakehead fish.
The Illinois Natural History Survey is testing options at its lab
in Havana on the Illinois River. Bighead carp dominate the river
there, after reaching the stretch in the mid-1990s.
``We'll catch easily 100 before we even get the net set,'' station
director Mark Pegg said.
In tests, electrodes were only 98 percent effective. The success
rate for a combination of underwater noise and a wall of bubbles was
Testing a combination of bubbles, noise and electrodes is next.
Then, heated water and a nitrogen plume that would suffocate the
channel as waste once did. Some suggestions are as simple as bringing
Mayor Richard Daley is lobbying Congress and agencies for more
barrier funding but is uncertain about the river-killing proposal,
city Environment Commissioner Marcia Jimenez said. She said the city
wouldn't endorse shutting off aerators ``without a great deal of
Even building a dam wouldn't guarantee protection against the
``Someone may like to eat them and decide it's a good idea to
release them,'' said Sarah Whitney, program manager with the Great
Lakes Commission in Ann Arbor, Mich.
Still, she said, there's no sense giving up.
``Otherwise I'd just go home and cry,'' she said.
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