might kill river to bar invaders
CHICAGO -- At one time the Chicago River was so polluted
that no fish could live there, and now scientists are
considering a long-shot idea to make it unlivable again
to prevent exotic species from using the river to migrate
between the Mississippi River and Great Lakes.
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 other undesirables.
"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 nature.
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 man-made waterway into federal compliance.
But now that the waterway can support native fish, non-native
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 Protection Agency.
Asian bighead carp are swimming in the other direction.
The 100-pound plankton-straining species was 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 chain.
As a coordinator at the agency's Rock Island office,
Rasmussen suggested river-killing among several options
in an analysis for cooperating agencies.
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
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
"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 about two-thirds.
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 in predators.
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 research."
Even building a dam wouldn't guarantee protection against
the Asian carp.
"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.